Cyclone and Storm Surge - Iczmpwb.org

HAZARD ASSESSMENT AND DISASTER MITIGATION
FOR WEST BENGAL DUE TO TROPICAL CYCLONES
Project sponsored by
Department of Disaster Management, Government of West Bengal
Report prepared by:
Indian Institute of Technology, Kharagpur
September, 2006

Acknowledgement
This project was completed with the help extended by many organizations and individuals, to whom
we are equally grateful. However, it is not possible to name all, and we wish to record our sincere
thanks to the following Government departments and offices:
1. Department of Disaster Management, Government of West Bengal
2. Department of Irrigation and Waterways, Government of West Bengal
3. Department of Land Records and Surveys, Government of West Bengal
4. Sundarban Development Board, Government of West Bengal
Acknowledgement
5. District Forest Officer, 24 Parganas (South)
6. Kolkata Municipal Corporation
7. Bidhannagar Municipal Corporation
8. Kolkata Port Trust
9. Kolkata Environment Improvement Project
10. Survey of India
11. National Thematic Mapping Organisation
12. India Meteorological Department
13. Census of India
14. Regional Remote Sensing Service Centre (ISRO), Kharagpur
We are also thankful to:
1. Sri Pijush Kumar Ghosh, Retired Superintending Engineer, I&W Department
2. Sri Tushar Kanjilal, Member, Sundarban Development Board

Project Team
Though the outcome of the project was mostly a combined effort of a joint team of researchers
belonging to various disciplines, the following broad areas were looked into by the experts mentioned
against each.
Overall planning and advice
Prof. S K Dube, Director, IIT, Kharagpur
regarding storm surge modelling
Project Team
Analysis of cyclone data and
assessment of cyclone hazard
Modelling of ocean hydrodynamics
and assessment of storm surge hazard
Vulnerability assessment
GIS integration, river flow modeling
and study of Kolkata and suburbs drainage hazard
Dr. M Mandal, Centre for Ocean, River,
and Land Sciences
Dr. P Bhaskaran, Department of Ocean
Engineering & Naval Arch.
Dr. Tarak Nath Mazumder, Department of
Architecture & Regional Planning
Dr. Dhrubajyoti Sen, Department of Civil
Engineering
An important component of the project has been the identification of the present bank and shorelines
of the rivers, alignment of the embankments, location of mangrove forest zones, along with other
land use patterns from satellite imageries. This was done by a team of scientists from the Indian
Space Research Organisation – Regional Remote Sensing Service Centre (RRSSC), Kharagpur.
Director (RRSSC) obtained special permission from the National Remote Sensing Agency (NRSA)
for availing LISS III as well as PAN data for the study area, for which the project team is immensely
grateful. River modelling was assisted by Dr. C Chatterjee, Department of Agriculture and Food
Engineering.

Contents
Preamble
Chapter 1 Introduction to hazard assessment and disaster mitigation study for West Bengal
Contents
Chapter 2
Tropical cyclones and their effects in West Bengal
Chapter 3
Effect of cyclones on Kolkata and surroundings
Chapter 4
Hazard analysis: cyclone and storm surge
Chapter 5
Vulnerability assessment for coastal districts of West Bengal
Chapter 6
Mitigation strategies and proposed measures for the districts
Chapter 7
Mitigation strategies and proposed measures for Kolkata and surroundings
Executive summary of recommendations
References

Preamble
The State of West Bengal, unlike others, is prone to a wide spectrum of natural hazards ranging from
landslides in hilly regions, flooding and bank erosion of rivers, earthquake, and devastations due to
cyclones. Of these, the last mentioned inflicts damage in many ways – generation of storm surge in
the ocean that lashes against the coast, the strong gusts of wind that threatens to wipe out villages,
and the extreme precipitation that causes drainage congestion, especially in urbanized areas. In a
way, cyclones form a veritable threat to nearly one-third of the state’s population that has the largest
concentration in the southern districts, which lie not very far from the Bay of Bengal, including the
state capital of Kolkata.
The report presented herein attempts to look into the threat perception to the State of West Bengal
and suggest possible mitigation measures. The mitigation measures suggested are in the lines of the
recommendations of the National Cyclone Risk Mitigation Project (NCRMP), like strengthening and
raising of embankments to prevent sea water intrusion and inundation, shelter belt plantations,
regeneration of mangroves, location of cyclone shelters, identification of missing road links, etc. In
addition, a detailed study has been done to analyse the effect of extreme cyclonic precipitation over
the city of Kolkata and its highly urbanized surroundings, though a threat to the city by way of
cyclonic storm appears to be rare but not impossible. This is proved by the records of 1737, when a
huge wave of water sweeping along river Hooghly cast off thousands of boats and ships along the
river. The accompanying storm is said to have devastated much of the city’s mud walled and
thatched houses as has been recorded in the registers of the East India Company.
This report has been attempted to be made as comprehensive as possible, taking into account every
minute detail available. However, it is natural that there could be some inadvertent lapses at some
places, for which we would look forward to any constructive suggestion. We would also welcome any
opinion that may enhance the completeness of this report.
Preamble
(Prof. Shishir Kumar Dube)
Director, IIT Kharagpur
Principal Investigator

Chapter One
Introduction to Hazard Assessment and Disaster
Mitigation Study for West Bengal
1.1. Motivation for the study
CHAPTER 1
The “Vulnerability Reduction & Sustainable Environment” chapter of the United Nations Development
Programme (UNDP) in its website http://www.undp.org.in/dmweb/default.htm presents a map (Figure
1-1) that shows the states most prone to severe cyclonic storms as being the coastal states of
Gujarat, Tamil Nadu, Andhra Pradesh and West Bengal.
Figure 1-1. UNDP map website showing the regions affected by strong winds and cyclones
According to the Indian Meteorological Department (IMD), the most destructive element associated
with an intense cyclone is storm surge. This may lead to inundations as well as coastline washouts.

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IMD, in its website (http://www.imdmumbai.gov.in/cycdisasters.htm) article on the surge prone coasts
of India also mentions that the vulnerability to storm surges is not uniform along Indian coasts. The
following segments of the east coast of India are most vulnerable to high surges:
1. North Orissa and West Bengal coasts.
2. Andhra Pradesh coast between Ongole and Machilipatnam.
3. Tamil Nadu coast, south of Nagapatnam.
It may be of interest to note that the West coast of India is less vulnerable to storm surges than the
east coast of India in terms of both the height of storm surge as well as frequency of occurrence.
The strong winds associated with a cyclone may destroy infrastructure, including dwelling houses
especially if these are the rural thatched types with mud walls. It must be remembered that the
regions very prone to cyclonic storms lie along the coastline and the socio-economic standard of the
people residing here is, on an average, rather low except for the few towns. It is also well known that
cyclonic storms are also associated with heavy precipitation. Hence, inundation by flooding due to
high rainfall is also considered as a disaster related to tropical cyclones.
The table of disasters in India (for the entire nineteenth century) presented in the UNDP website
under the title “Disaster Related Database” also shows that the State of West Bengal has suffered
the worst due to cyclonic storms, followed by floods, droughts and earthquakes. Hence, the present
task of evaluating the hazard caused by cyclones to the state and recommendations of mitigation
measures has been the result of a prudent and timely decision.
1.2. Background, key concepts and methodology
The project was initiated at the request of the Department of Relief, Government of West Bengal after
an initial meeting that took place in June, 2005 at Writer’s Building’s, Kolkata. It emerged from this
and the subsequent meetings that the loss of lives and property due to cyclones having been quite
heavy for the State, there is an urgent need to evaluate the hazard and vulnerability of the different
cyclone prone regions and suggest possible disaster mitigation measures. It was also decided that
the suggestive measures should more or less be in the lines of National Cyclone Risk Mitigation
Project (NCRMP) guidelines.
The core of the project lies in the determination of the following:
1. Hazard analysis: This includes the study of cyclone tracks and related information for past
years as available and evaluation of the hazard to the different parts of the state that are

1.3
most likely to be affected by its effect. Since historical records would show a range of storms
varying from the most severe to the mild, it would be necessary to categorise the storms and
decide upon a certain feasible storm intensity which may practicably be countered by the
various risk mitigation measures. Adoption of a very severe storm is likely to lead to an
uneconomical solution. In addition, study of the storm surges likely to be generated by the
action of cyclones. This has to be tested with the most severe as well as the most practicable
storm as obtained from the cyclone data analysis as mentioned in the paragraph above.
Conditions of simultaneous occurrence of high tides have also to be kept in mind. A study of
river water level rise due to the rise of the ocean water level as a result of the storm surge
coupled with high tide as explained above is necessary. The upland discharge has also to be
considered, since a higher discharge may lead to a higher elevation of the river water level.
Study of water logging scenario in the urban cluster of the State capital of Kolkata and its
surroundings due to heavy precipitation resulting from tropical cyclones is a part of the urban
hazard analysis due to cyclones.
2. Vulnerability studies: Vulnerability or susceptibility is related to the characteristics of the
region and has to be studied in detail after dividing the study area (in this case the cyclone
prone region of the State) into appropriate units. In the present study, it was decided to
choose the Development Block as one unit while studying the vulnerability vis-à-vis the effect
of cyclones. It may be remembered that assessing the vulnerability of human settlements is
an important task, which can be correctly assessed by taking into account the following
factors (a) Shelter type including construction material, (b) Physical connectivity, including
road and navigation network, (c) Local economy, (d) Physical infrastructure, (e) Social
infrastructure, and (f) Incidence of disaster impact on various socio-economic groups.
3. Mitigation measures in the form of embankments that may be newly constructed or the older
ones strengthened. In the coastal districts of West Bengal, especially in the Sundarban
region, the 54 of the 102 islands of the river Ganga estuary are inhabited and most of them
are enclosed by circuit embankments. Many of these embankments are more than a century
old and not constructed according to scientific principles. These need strengthening.
4. Mitigation measures in the form of mangrove plantations that may protect the embankments
from getting eroded or shelter belt plantations that may lessen the impact of the severe
storms moving inland.

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5. Proposals for location of cyclone shelters and suggestions for missing road links. These
have to be done on the basis of the vulnerability studies.
6. Proposals for suggesting relief to the urban dwellers of Kolkata by way of removing storm
water in a more effective way and prevent congestion of water in the streets during a
cyclonic depression.
1.3. Scope of the work and limitation
In order to effectively tackle the project in the limited time available, it was decide to depend upon
secondary data as available from various sources. The scope of the work thus includes the collection
of appropriate data, both in the form of statistics and written documents as well as in maps and
integrating them together to form an overall database useful for the study. The cyclonic storm data
have been obtained from the Indian Meteorological Department. The bathymetry of the oceans,
particularly the Bay of Bengal has been obtained from an international website. The present day
location of embankments and mangrove forests have been derived from satellite imageries, with the
help of the Regional Remote Sensing Service Centre (ISRO), located within the campus of IIT
Kharagpur. The bathymetries of the rivers have been obtained from the Kolkata Port Trust. Details of
embankments have been acquired from the Irrigation and Waterways Department, Government of
West Bengal. The details about the storm water disposal of the city of Kolkata have been derived
from the information supplied by the Kolkata Municipal Corporation. The base map for preparing the
GIS integration was done from the topo-sheets of the Survey of India. The Development Block
boundaries were digitized from the District Planning maps of the National Thematic Mapping
Organisation. The Block-wise statistics on housing was extracted from the Census of India data.
The basic data collected above was integrated into a GIS database that provided the framework for
further analysis. The storm surge analysis was carried out by the IIT Delhi numerical model and the
river flood analysis was done with the help of the software MIKE FLOOD, a numerical simulation
model of DHI. On the basis of these studies, appropriate mitigation measures have been suggested,
which are in line with those suggested by the various technical departments of the Government.

Chapter Two
Tropical Cyclones and their Effects in West Bengal
2.1. General Introduction
Technically, the cyclone affecting the coast of West Bengal, and indeed the remaining of coast of the
country, is called the Tropical Cyclone which is a storm system with a closed circulation around a
centre of low pressure, driven by the heat released when moist air rises and condenses. As the name
suggests, the origin of these is in the tropics and has an anticlockwise circulation in the northern
hemisphere. Tropical cyclones can produce extremely high winds, generate torrential rain, and drive
up the ocean water against the coast resulting in a storm surge. The effects of a cyclone on a
population can be catastrophic and as has been recorded in the historical annals of exceptional
cyclones, the storm of 1737 has been one of the worst, which had devastated the city of Kolkata
(Calcutta then). Though many accounts prevail, Bilham (1994) evaluates the event more rationally by
examining many contemporary documents and concludes that a cyclonic storm had caused a huge
wave to rush up the river Hooghly (reportedly 40 feet high) and destroy many fishing boats and ships.
Evidences also show that the strength of the storm had caused destruction of most of the thatched
houses belonging to the local population. The spire of St. Anne’s church within Fort William (later
destroyed during Siraj-ud-Daula’s campaign) had probably toppled due to the gust of the cyclonic
winds. Though this kind of cyclonic devastation has not been experienced by Kolkata since then, but
it may be presumed that such an event could have been one of an extreme kind in which the cyclone
track had been coincident with the path of the river Hooghly. This might explain the huge upsurge of
a wave and devastation of houses by winds. It is possible that the waves penetrated 60 leagues
(nearly 300 kms) inland from the mouth of the bay, as one may see from the remnants of the mast of
the Portugese ship that ran aground near Bandel and has been kept for public viewing at the old
church compound there.
CHAPTER 2
Other notable cyclones originating in the northern Indian Ocean are seen to have either hit the coast
of West Bengal or have grazed menacingly close by. For example, the severe tropical cyclone hit
Kolkata in 1864, reportedly killing nearly 60,000 people. This event and the subsequent famines in
1866 and 1871 led to the formation of the India Meteorological Department. The cyclonic devastation
of October 1942 is also reported to have been quite high, with wind speeds and Sagar Islands being
recorded to be as high as nearly 165 km per hour. The next severe cyclone that finds mention in this

2.2
region is that which struck the south eastern coast of present Bangladesh in November 1970, just a
few months ahead of the foundation of the country. The extent of devastation had been huge –
reportedly 5,00,000 dead and 1,00,000 missing thus distinguishing it to be one of the worst natural
disasters of modern times. A perusal of the storm track indicates that it had moved uncannily close to
the shores of West Bengal, and one may imagine the grave consequences had the path been just
deviated to make a landfall here.
The next two severe cyclones, however, have luckily spared West Bengal – the first one being the
1991 cyclone that made landfall at Chittagong in Bangladesh and the second being the 1999 Orissa
cyclone that hit Paradeep port badly. In either case, much of the deaths were by flooding caused by
the torrential rains generated as a consequence of the storm.
Figure 2-1. Tracks of all the major tropical cyclones in the Bay of Bengal since 1970

2.3
Tracks of cyclones from 1970 till date, plotted on a map of the Indian Ocean, is available from the
web-site http://en.wikipedia.org/wiki/Tropical_cyclone and has been reproduced in Figure 2-1. It may
be noted that the strength of the cyclones shown in the map have been categorised according to the
Saffir-Simpson scale, which is described briefly in Table 1.
The authors of this report are greatly thankful to user Nilfanion of Wikipedia for the image provided in
the web-site. The tracking data used is from the Joint Typhoon Warning Center, which is a joint
United States Navy–United States Air Force task force located at Naval Pacific Meteorology and
Oceanography Center in Pearl Harbor, Hawaii, USA.
Table 2-1. Strength of tropical cyclones classified according to the Saffir –Simpson scale
Category
Wind speed (km per hour)
5 ≥250
4 210–249
3 178–209
2 154–177
1 119–153
Tropical storm 63–117
Tropical depression 0–62
Some of the other important tracks, posted in the Wikipedia website under the topic of tropical
cyclones (http://en.wikipedia.org/wiki/Tropical_cyclone) are given in Figures 2-2 to 2-4.

2.4
Figure 2-2. Track of the 1970 Bhola (Bangladesh) cyclone
(Change of strength is not clearly shown, but is estimated to be definitely on the higher side of
magnitude 5)
Figure 2-3. Track of the 1991 Bangladesh cyclone

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Figure 2-4. Track of the 1999 Orissa cyclone
2.2. Impact on life and property
A mature tropical cyclone can release heat at the rate of 6x10 14 Watts or more (NASA, 2000). The
most devastating effects of a tropical cyclone occur when they cross coastline, making landfall.
India Meteorological Department (website: http://www.imdmumbai.gov.in/cycdisasters.htm), mentions
that there are three elements associated with a cyclone, which cause destruction. These are:
• Cyclones are associated with high-pressure gradients and consequent strong winds. These,
in turn, generate storm surges. A storm surge is an abnormal rise of sea level near the coast
caused by a severe tropical cyclone; as a result, sea water inundates low lying areas of
coastal regions drowning human beings and livestock, eroding beaches and embankments,
destroying vegetation and reducing soil fertility.
• Very strong winds may damage installations, dwellings, communication systems, trees, etc.
resulting in loss of life and property.
• Heavy and prolonged rains due to cyclones may cause river floods and submergence of low
lying areas by rain causing loss of life and property. Floods and coastal inundation due to
storm surges pollute drinking water sources.
It may be mentioned that all the three factors mentioned above occur simultaneously and, therefore,
relief operations for distress mitigation become difficult. So it is imperative that advance action is
taken for relief measures before the commencement of adverse weather conditions due to cyclones.

2.6
The most destructive element associated with an intense cyclone is storm surge. Past history
indicates that loss of life is significant when surge magnitude is 3 metres or more and catastrophic
when 5 metres and above.
As mentioned in the previous section, cyclones have resulted in rather high damage, especially to the
coastal areas. A list of the available data on losses due to cyclones in West Bengal has been
provided by the Department of Relief, Government of West Bengal, and is attached as Annex – I.
The cause of losses in rural and urban areas due to tropical cyclones is presented in the following
sections.
There are secondary hazards too. Some of these are:
• Spread of epidemics – The wet environment in the aftermath of a tropical cyclone,
combined with the destruction of sanitation facilities and a warm tropical climate, can
induce epidemics of disease which claim lives long after the storm passes. Infections of
cuts and bruises can be greatly amplified by wading in sewage polluted water. Large
areas of standing water caused by flooding also contribute to mosquito-borne illnesses.
Drinking water also gets polluted resulting in diseases like gastro-enteritis.
• Power cuts – Tropical cyclones often knock out power to an area prohibiting vital
communication and hampering rescue efforts.
• Damages to communication links – Tropical cyclones often destroy key bridges,
overpasses, and roads, complicating efforts to transport food, clean water, and medicine
to the areas that need it.
2.3. Areas under the threat of damage from tropical cyclones
The regions of West Bengal that may suffer the possible impact of tropical cyclones come belong to
the following districts:
1. East Midnapore
2. 24 Parganas-South
3. 24 Parganas-North
4. Howrah
5. Hooghly
Of course, the areas prone to devastation under each district vary according to the location. For
example, the Blocks along the coastal region of West Bengal (Figure 2-5), being low lying, are

2.7
affected most. Here, the the landfall of the cyclone occurs and the dangers of inundation by storm
surges as well as destruction of low-cost houses due to strong winds reign supreme. Also, the
geographical location of this region is such that it has high chances of cyclone landfall. Though the
Blocks of the East Midnapore are as close to the Bay of Bengal as those of the 24 Parganas-South,
the alignment of the coastline here and the geographical location makes the probability of landfall
rare. Of course, the rise in ocean level caused by a storm track grazing close by, may nevertheless
cause inundation. Some portions of the Districts of 24 Parganas-North and Howrah though not
coming very close to ocean, still suffer from the impending threat of river level rise due to a rise of the
ocean level caused by a cyclone induced storm surge. The District of Hooghly is much inland, but as
the event of 1737 had proved, a probable track of a tropical cyclone being incidentally aligned with
the axis of the river Hooghly may cause a violent upsurge, especially since the water rushing up from
the estuary would have to move up through the river where the width is relatively narrow.
In most of the Blocks in the coastal West Bengal, and especially in the District of 24 Parganas-South,
the land is rather low lying and the habitation areas along with the neighbouring agricultural fields are
protected by embankments. The adjoining region to the east is the world famous mangrove forest of
the Gangetic delta – The Sundarbans. In order to appreciate the magnitude of the cyclonic hazard
and the means adopted to mitigate consequential damages, it is necessary to review the
geographical and historical situations in these areas before and after the establishment of substantial
habitation from its pristine characteristics of a marshy and swampy land.
The State capital Kolkata also falls in the cyclone prone region, as stated before. However, the urban
characteristics of Kolkata and its surroundings distinguish the damages here from that of the typical
rural countryside of the Districts. The types of problems facing Kolkata and its neighbouring urban
regions have been discussed separately in Chapter 3. In the present chapter, discussion is restricted
to the region other than Kolkata.
2.3.1. Geographical extent
The coastal region of the State of West Bengal is prone to the effects of cyclonic storms. Broadly, the
West Bengal coast can be divided into two parts, on either side of the mouth of the river Hooghly.
This may be seen from Figure 5 which illustrates the Development Blocks of the districts of Medinipur
east and 24 Parganas South that hug the Bay of Bengal. Towards the east are the Gangetic deltaic
tracts which are mostly shoals, sand spits, mud flats and tidal swamps and flats and towards the east
are the Medinipur coastal plains which comprise of mostly sandy beaches. The geophysical nature of

2.8
the two regions is rather different. Further, the nature of the action of cyclonic storm surge depends
upon the geophysical characteristics of the coastline or the estuarine bank-line.
Figure 2-5. Coastline of West Bengal showing the different Blocks touching Bay of Bengal
Physiographically, the coastal plain of West Bengal may be said to consist of the following five
different types of features: (i) Beaches, spits and barriers; (ii) Coastal sand dunes; (iii) Coastal
wetlands; (iv) Coastal lowlands; and (v) Coastal plains, estuaries, tidal inlets and lagoons (Paul
2002). Each of the physiographic regions is characterized by several morphological features evolved
under the impact of coastal hydrodynamics, available sediment supply and transportation paths, selfcompaction
of sediments, sub aerial processes, changes in relative level of land and sea, etc.
According to Chakrabarti (2006), in West Bengal two contrasting coastal environments are present:
(a) the Macrotidal Hooghly estuary and (b) the Mesotidal Midnapore coastal plain in the east and
west respectively of the River Hooghly:
• Macrotidal (tidal range > 4m) Hooghly estuary — the bell or funnel shaped Hooghly river
mouth characterized by a group of islands set in a labyrinth of tidal creeks marking their
outlines. This macrotidal domain with bidirectional tidal currents is marked by the presence of
'sickle-shaped' near offshore configuration with partially or totally emerged linear tidal shoals

2.9
(aligned perpendicular to the shoreline) separated by intervening swales e.g. Jambudwip and
Chuksardwip.
• Mesotidal (tidal range: 2—4m) Midnapore (Digha—Junput) coastal plain to west of the
Hooghly estuary. Successive rows of dunes with intervening clayey tidal flats are
characteristically present in the coastal plain.
The “Ancient dune complex” all along the Midnapore coastal plain (about 10 to 15 km north of the
present shoreline) indicates the position of the “Ancient strand line” in the area. The C 14 dating of
sediments from “Ancient fluvio-tidal flat” (5760±140 YBP) present in the north of the “Ancient dune
complex” confirms that the higher strand line in the post-glacial (Holocene) period is at present
represented by the “Ancient dune complex” which is around 6000 YBP – the optimum of the
Flandrian transgression (Selby, 1985). The C 14 dating of sediments from “Ancient intertidal flat” (just
south of the “Ancient dune complex”) gives an age of 2920±160 YBP which indicates the first
punctuation in the regression of the Holocene sea in the area under consideration.
The “Ancient dune complex” does not extend in the eastern part of the Hooghly river. Careful
analysis of the satellite imagery reveals the presence of a morpho-structural lineament in the same
alignment as that of the aforesaid dune belt and passes just north of Sagar Island, through Kakdwip,
in a north-easterly direction towards Bangladesh separating the lower deltaic plain of Ganga-
Brahmaputra (within India) into two sectors, as mentioned below:
The areas to the south of this line are characterised by the presence of islands (draped with
mangroves) separated by an network of active tidal creeks,
The areas to the north of this line are almost free from such network embroidery of tidal creeks and
islands. The Sundarban falls in the first group occupying the area south of the lineament. In Hooghly
estuary, in the south of this morpho-structural lineament, the sticky grey clay of inter-distributary
mangrove marsh unit (equivalent to the “Ancient intertidal flat” unit of Midnapore coastal plain) is
characterised by the brackish water mangrove bio-assemblages (for example Ceriops, Rhizophora,
Chenopodiaceae, Heriteria, Gramine (Poaceae), Palmae (Aricaceae), Circulisporites etc.). The C14
dating of this clay sample from Namkhana giving an age of 3170±70 YBP and 2900±20 YBP from
Gangasagar indicates the progressive southward shifting of coastline towards the present shoreline
in recent past.
We briefly discuss each of these coastal zones and the vulnerability due to cyclonic hazards in the
following sections.

2.10
2.4. The eastern coastal zone – the Sundarbans
The Sundarbans consists of the Coastal belt of the Bay of Bengal on the Southern most fringe of the
State of West Bengal and Bangladesh, It forms part of the Gangetic Delta which has been built
primarily by the silt, carried down by the Ganga and Brahmaputra river system bounded by river
Hooghly on the west and Padma - Meghna on the east. The land is very fertile. The total expanse of
the Sundarbans is above 2.07 Million Hectares out of which only 38.54 percent, that is, 0.791 Million
Hectares lie in India and the rest in Bangladesh.
The Sundarbans area is situated in the Southern portion of the District of 24-Parganas bounded by
the river Hooghly on the west, Bay of Bengal on the South and Ichhamati-Kalindi-Raimangal river
system on the east bordering Bangladesh. The northern boundary was demarcated from the rest of
24-Parganas district in 1831 by Survey of India by means of what is known as the Dampier-Hodges
Line, This line runs a slightly zig-zag course from Ichhamati near Basirhat in the North-east to the
Hooghly near Kulpi in the South-west.
Figure 2-6. The Sundarbans of West Bengal – reclaimed areas and the existing forest areas
(From Paul, 2002)

2.11
2.4.1. Physical features
The major portion of South Bengal including the Sundarban had been formed mainly by the service
tendered by the magnificent river Ganga in transporting millions tons of silt every year from the
Mighty Himalayas through the Bhaqirathi Hooghly channel. Land was formed at the head of delta due
to deposition of silt in suspension when the strong current in the river is checked by coming in contact
with the sea. Ganges like other delta builders, began to approach the sea in several diverging
branches enclosing the intersecting the delta already built so as extend it towards the sea by
dropping their silt load near about their mouths. But the raising would have beer, exceedingly slow as
floods occur only in limited period during the monsoon. Hence Nature has requisitioned the service of
tide who pick up vast reservoir of unconsolidated silt at their mouths almost to the saturation point
and flow inland twice a day during flood tide through out the year and drops a part at low velocity
stage on the entire basin below tide level and within tide limits and thus raise the delta already built.
The process of delta building was very high for the two following factors -
i) The steep slope of the Himalays, the highest mountain in the world which aided by the
torrential character of the rain and the rather indifferent conditin of the catchment basin has
been furnishing the building material in abundance during the monsoon.
ii)
The abnormally high tidal range due to the funnel shape of the Bay of Bengal which has been
helping in distributing these materials twice daily throughout the year. But, silt is less in
winter season particularly.
The formation of delta in Southern Bengal continued at a very fast rate upto 12th Century. Between
the l2th and 16th centuries A.D., the main course of the Ganga fluctuated between the Bhagirathi-
Hooghly and the present course further eastwards called the Padma, and from the 16th century
onwards the Padma has become the main course. With this diversion of the main Ganga through the
Padma, all the branches of the Ganga Bhagirathi system in this region, which were carriers of silt
were deprived of their head water supply except during the few monsoon months. As such these
rivers have lost their role in building the delta. At the moment, new land formation is dependent on
tides. The old river channels excepting Hooghly exist as tidal creeks with the additional function as
drainage carriers of the area.
2.4.2. Topography
The depth of silt deposited by upland floods is the maximum close to the river banks where the

2.12
velocity is first checked. As the spilling proceeds away from the river banks, the silt content of the
spilled water and consequently the depth of silt deposited is less and less. The area lying midway
between two adjacent flood carriers is lower than the two banks. But the tides by their constant
movement distribute the unconsolidated silt charge uniformly over the entire basin and raise the
inside valley almost to same level as that the bank. Thus the general topography is very flat.
The North Eastern area (Haroa-Minakhan-Sandeshkhali) area being close to Calcutta had been
prematurely reclaimed much earlier than the south West area (Kakdwip – Sagar – Pathar-protima
area) by marginal embankment and hence has been deprived of natural raising by flood and tide.
The average ground level in above mentioned North-eastern and South-Western area is around 1.2m
and 2.0m above Mean Sea Level respectively against mean high water level of 2.75m (H.F.L at sea
wall zone is approximately 3.5m).
2.4.3. Rainfall, Temperature and Humidity
The total average rainfall in the area is 1625 mm. In some abnormal years this exceeds 2000mm and
in some subnormal years it is as low as 1300 mm. South Westerly Monsoon generally breaks up on
8th June and recedes on 20th October. Approximately 73.2 percent of the annual rainfall occurs in 53
days within 124 days monsoon season. Though the maximum daily rainfall during the monsoon
seldom exceeds 300 mm a rainfall of as high as 800 mm in a period of four consecutive days was
recorded in September, 1900. The pattern of rainfall in the district of 24-Parganas (North and South)
where Sundarban is situated is given in Table 2-2 below: -
Table 2-2. Average monthly precipitation in Sundarban area of West Bengal
Month
Average monthly rainf Monthly rainfall
(mm)
percentage
average Rainfall
Average Rainy days
month
January 5.59 0.3 0.49
February 19.05 1.2 0.45
March 34.80 2.1 1.78
April 63.00 3.9 1.73

2.13
May 126.00 7.8 4.98
June 260.10 16.0 11.55
July 358.65 22.1 15.27
August 326.14 20.1 13.55
September 243.31 15.0 12.26
October 130.60 8.0 6.38
November 51.56 3.2 2.05
December 6.09 0.4 0.50
Total 1625.09 100.0 71.0
The mean maximum and minimum temperatures are about 32°C and 15.7°C occurring in May &
January respectively. The temperature begins to rise from early February & starts falling from mid-
October. Southerly winds start blowing from the middle of March and Nor’westers make their
appearance in April and May. The humidity is about 86 percent of saturation from mid-June to mid-
October and is about 75 percent in winter.
2.4.4. Winds
Strong winds provoke two phenomena: wind set-up and wind waves. Long lasting wind, blowing in
the same direction, like the monsoon, leads to a raise of the mean sea level near the lee-side coasts,
which increases the high water levels but also the low water levels. This phenomenon is known as
wind set-up. Usually the tidal amplitudes reduce when the mean sea level rises.
The long lasting wind causes a water flow in the direction of the wind near the surface which in turn
results in a flow in the opposite direction near the bottom. This return flow near the bottom carries
sometimes significant volumes of silt towards the sea.
Another phenomenon is the wind waves. These waves develop on top of the wind set-up. They are
not only formed at sea but also in the wide sections of the network of waterways in the Sundarban
area. The height of the waves depends on the velocity of the wind, the fetch; this is the length the
wind skims over the water surface, and to a lesser extent on the water depth, assuming that the
duration of the wind is long enough to allow the waves to be fully developed.

2.14
Strong winds known as cyclones occur along the coasts of West Bengal and Bangladesh. Most of the
tropical cyclones manifest themselves in April/May or October/November. Wind velocities of 200
km/hour can occur during strong cyclones. The wind velocity reduces rather fast when it blows over
land. This is discussed I n the next section.
When the wind waves reach the coast there are two effects that can cause damage to the shore or to
the embankments built by mankind to protect the land. The first effect is known as wave rush-up. By
the force of the waves water is rushing up the slopes to a higher level than the level of the top of the
waves in open water. The second effect is wave dash. Water is smashed with force against the slope
of the natural or artificial embankment which might cause damage to these slopes and eventually the
entire embankment.
2.4.5. Cyclonic storms
The reasons for the development of tropical cyclonic storms are many amongst which the most
important is the prevalence of moist warm winds. Hence they occur mostly during the period front
April to the end of November when South westerly winds blow more or less steadily over the Bay.
Cyclonic storms grow gradually till the maximum intensity is reached. The depth of the lowest
barometric pressure and the extent of the wind field are the most important parameters influencing
this intensity. Some stormy extend over a wide area but have only a weak pressure gradient while
others are more concentrated over a small area but have a great pressure gradient. High wind
velocities occur only in, regions of limited extent along the storm track through which the cyclone
passes.
The wind pressure causes an upsurge of the water levels and lead to high water levels much higher
than the predicted High Water 1evel based on tidal influence. As such cyclone storms and the
resultant surge levels are very important from the hydraulic point of view in as much as they influence
the levels up to which water may rise and the levels up to which protection is desired severe cyclones
may cause heavy devastation especially if the storm surge occurs in synchronisation with high tides.
The high waves generated attack the shore and embankments at great velocities. The most severe
cyclone within recorded memory occurred in October 1942 when there occurred wide devastation
along the West Bengal coast. The maximum wind speed recorded during this storm was about 165
km per hour in Sagar Island. The maximum height of water level was about 3.5 meters above the
predicted high water level and about 2 Meters above the highest high water level recorded during
other storms. This storm is of course one of an extremely rare occurrence.

2.15
During the months of November to May depressions are formed in the lower region of the Bay and
hence rarely reach the coast of the Sundarbans. The period during which cyclone storms affect
Sundarbans is between June and October out of which October is the most dangerous month of the
year when South West monsoon starts receding and North West wind starts stepping in.
Most of the tropical cyclonic storms cross the shore having average speeds varying between 25 and
75 km per hour. During the 60 years from 1907 to 1966 there were as many as 108 tropical cyclonic
storms of velocity above 25 km per hour crossing the Sundarbans coast. The wind – speed wise and
month – wise distribution is as given in Tables 2-3 and 2-4.
Table 2-3. Wind statistics recorded at Sagar Island
Wind speed in Number of Occurrenc Percentage
km per hour
25 31 29
50 30 28
75 25 23
100 11 10
125 10 9.9
150 1 0.1
175 - -
Total 108 100
Table 2-4. Number of occurrences of tropical cyclonic storms at West Bengal coast
Month Number of Occurrence Percentage
January 0 0
February 0 0
March 0 0
April 0 0
May 4 4
June 9 8
July 28 26
August 31 29
September 16 14.5
October 17 15.5
November 3 3
December 0 0
Total 108 100

2.16
2.4.6. Soil characteristics
The area is covered with alluvium which is of great depth, Soil is heavy clay impregnated with salt.
The deposit is made up of washing as a result of denudation of the Himalayas. Deep boring indicate
that the alluvium consists of alternate bands of clay, sand and silt together with a few bands of
gravel. Excavations and borings have revealed in some places the debris of ancient forests.
The soil in the Sundarbans can be classified into four categories, viz:
• Clayey Soil (Matial)
• Loamy soil ( Doash)
• Sandy Soil (Balia)
• Saline Soil (None)
Clayey soil (Matial) is the most predominant and is of great natural fertility on which all kinds of crops
are grown. Winter rice is grown in abundance in this soil. Loamy soil (Doash) is a mixture of lay and
sand. It is also suitable for agriculture particularly for Rabi crops and Sugar cane as it retains
moisture for a long, time. In sandy loam (Balia) the proportion of sand exceeds that of clay and is
suitable for Aus rice and potato. Saline soil (Nona) is generally wet and is not suitable for cultivation
of crops. It only bears Ulu grass used for thatching.
2.4.7. River system
The whole of the Sundarbans area is interspersed with an intricate network of crisscrossing channels
and creeks, big or small which divide the area into large number of islands. These channels
ultimately find their way to the Bay of Bengal through one or other principal estuaries. Starting from
the west these are the following:
Hooghly - It gets a partial discharge of Ganga through
Farakka Barrage as also the run-off Western rivers
such as Mayurakshi, Ajoy, Damodar etc.
Baratala or Muriganga - A branch of Hooghly carrying about 16 percent of
upland discharge of Bhagirathi-Hooghly which
separates Sagar Island from main Sundarbans.

2.17
Saptamukhi : - Purely tidal river
Thakuran - -do-
Matla - The River Bidyadhari which served as an Outfall
channels for the storm water & sewage of Calcutta
in the post and is completely dead now forms the
upper reach of Matla. Now it is purely tidal river.
Gosaba - Purely tidal river
Haribhanga - -do-
Raimangal - Previously it used to receive upland discharge of
Ganga through its branch 'Jamuna' which had been
purely cut of since 16th century. Now it is
practically a tidal river.
Figure 2-6. The major rivers of Sundarbans in West Bengal

2.18
All rivers have in general southerly course towards sea. Some of the above major rivers braids into
more than one channel before meeting the sea. Except river Hooghly and river Baratala all rivers are
actually tidal waterways without any upland discharge expecting run off of small localised catchment
and their water is as salty as the sea.
Between the large estuaries and rivers are innumerable streams and water courses called khals,
forming a net-work of channels, some ending ultimately in little channels that serve to draw off the
water from each block of land. Each block is formed like a saucer with high ground along the bank of
the Khals surrounding it, and with one or more depressions in the middle. The rain water in the block
is drained off by the little khals into the larger khals and ultimately to the Sea through the rivers during
Ebb tide, conversely when the water swells in the rivers during Flood tide it floods the country
through the same channels. Many of the khals connect two large ones, and consequently the tide
flows into them through both ends. Such khals are called “Do-Aniya" Khals. They are very useful as
affording communication between the larger khals, but have one serious defect that they are liable to
silt up at the point where the two tides meet, for the water in always still there.
Even the major rivers in the Sundarban region flowing East of the Hooghly river have relatively small
catchment areas and consequently the discharges from the hinterlands are small in comparison with
the volumes of water which flow in and out each tide. Therefore, the currents in the maze of rivers
and creeks of the Sundarban Region are almost entirely the results of the fluctuation of the sea level
in the Bay of Bengal and the way these fluctuations propagate themselves within the system of
waterways of the delta.
2.4.8. Tides
Tides are generated in the Bay of Bengal by the forces of attraction of mainly the sun and the moon
upon the rotating earth. The effect of tide is manifested in a regular alteration of rise and fall of the
water level of the sea and the estuarine channels and creeks, with the advent of rising tide, the water
level of the Sea Starts rising gradually and steadily till a highest level known as the “High Water
Level” (HWL) is attained. This rising phase of the tide is called the “Flood tide” or the “Flow tide”.
After the attainment of HWL the tide water level starts falling gradually and steadily till a lowest water
level (LWL) is reached. This falling phase of the tide is called “Ebb tide”. Thereupon the tide water
starts rising once again till the occurrence of the next HWL and so on. The difference in elevation
between a HWL and the next LWL is called the “Tidal range” and the period intervening any two

2.19
consecutive HWL or LWL is termed the “Period of Tidal Circle” which is on averages is 42 hours 24
minutes, The tidal cycles are represented graphically by tidal curve.
With the advent of flow tide, the velocity of current which is in the inland direction starts increasing,
reaches a maximum at about the middle of the flow tide and beginning to decrease thereafter being
zero at the HWL which is known as “High Water Slack”. Thereupon, the ebb tide commences and the
current velocity which is in the seaward direction starts increasing once again and after attaining a
maximum value begins to diminish gradually becoming zero at LWL which is known as the “Low
water Slack”. Two tides called “Semi-diurnal tides” occur in course of every lunar day. The tidal
ranges of the two semi-diurnal tides are also found to differ from each other. Table 2-5 gives the list
of highest High Water Level (HWL) recorded at Sagar Islands.
Table 2-5. Year-wise High Water Levels (HWL) at Sagar Island for the period from 1934 to 1976.
All levels are in Meters and refer to G.T.S. Datum.
Year H.W.L. YEAR H.W.L.
1934 3.47 1956 4.33
1935 3.72 1957 3.92
1936 3.77 1958 3.92
1937 3.47 1959 3.74
1938 3.51 1960 3.64
1939 3.72 1961 3.72
1940 3.44 1962 4.11
1941 3.41 1963 3.64
1942 5.61* 1964 3.79
1943 3.57 1965 3.62
1944 3.59 1966 3.59
1945 3.62 1967 3.45
1946 3.36 1968 3.05
1947 3.41 1969 3.14
1948 3.51 1970 3.45
1949 3.72 1971 3.36
1950 3.77 1972 3.63
1951 3.57 1373 3.13
1952 3.92 1274 3.13
1953 3.95 1975 3.25
1954 3.74 1976 3.61**
1955 3.69
* The H.H.W.L. of 1942 could not be recorded on the gauge but was estimated from flood marks.
** The H.H.W.L. of 1976 during the severe cyclone of September 1976 could not be recorded on the
gauge and the stated value excludes the H.H.W.L. of September.

2.20
Another interesting feature of tides lies in the fact that the tidal range at any location fluctuates
steadily and gradually from day to day in accordance with the lunar phase. The tidal range at the full
and new moons is found to the maximum. This phase is called the "Spring Tide". After the
occurrence of the spring tide at Full moon or New Moon the tidal range starts diminishing till the
occurrence of the Neap Tide at the middle of moon cycle when the tidal range is the minimum.
The tidal curve at the sea face of a tidal estuary in Bay of Bengal is found to have a symmetrical
harmonic shape. The periods of both flow and Ebb tide being practical1y equal. As it goes upwards,
the period of Ebb tide increases more than the low tide. Thus the f low velocities are more than the
subsequent Ebb velocities along the tidal channel as one proceeds upwards. There is another
interesting point in this connection: the tidal range starts increasing steadily and gradually upwards
from the sea face, attains maximum value at the certain points and starts diminishing thereafter till at
the terminal point of tidal propagation it becomes practically nil.
The water levels at the confluences of the major rivers with the sea are constantly changing due to
the tides. These changes propagate into the Sundarban not only along their own courses but also
along the many bifurcations, changing with varying time-lags the water levels at both ends of each
river - or creek section, initiating a pattern of flows in the various waterways.
Due to erosion and sedimentation the average depth of many sections of the system of waterways
change; some sections will become deeper others less deep. A change of the size and the shape of
any individual section do not only change the flow through this section, it will also alter the pattern of
water movements during the process of filling and emptying the live storage of the Sundarbans. The
following case studies have been taken from Kanjilal (2006).
An example of this can be seen presently in the Bidya river. There is a strong sedimentation in the
section of this river from its confluence with the Gomar river till the confluence with the rivers Kartel
and Durgadoani. Because of this the propagation velocity in this section is reduced and dur-ing rising
tide the water level near the latter confluence will rise slower than it did before. Due to this a larger
difference in water level is created not only in this section of the Bidya river but also in the Kartel and
the Durgadoani river. The slope in all three sections is increased.
As a result of the reduced wetted cross-section of the discussed part of the Bidya river, this extra
slope will not lead to a larger discharge; the discharges of the two other rivers increase however. Due
to this the erosion in those rivers became stronger and is endangering the stability of the river banks.
This is significant near the market place at Basanti and at many other places along both rivers.

2.21
Considering all the interdependencies in relation to the distribution of the flows over the many river
sections, proposed human interventions to alter or to stabilize the course, the size and the shape of
any section should not only be valued on their effects on the local situation and their sustainability but
also on the changes these interventions might initiate in the pattern of flows and discharges in the
adjacent river sections.
At present not much information is available about the configuration, the fluctuations of the water
levels and the pattern of flows which are the results of the combination of storage and the
propagation of the tide.
Whatever the configuration of the maze of waterways might be and whatever the sizes and the
shapes of the river sections might have, their various average depths are smaller during low tide than
during high tide. Incoming tide starts with certain depths and these depths will increase till the end of
the incoming tide. With outgoing tides however the depths will become less from its start till its end.
Due to this and the effects on the propagation velocity, the period of incoming tide will become
shorter and the outgoing tide will become longer for the river sections according as their distance to
the sea. As the volumes that are moving in and out are about equal, the incoming currents are
stronger than the outgoing for all sections except those very close to the sea; where the currents are
equally strong. This phenomenon is important for the process of erosion and sedimentation in the
estuary.
2.4.9. Role of tidal channels
The energy which creates the tidal flow, viz. attraction of the sun and the moon in the deep sea, is
manifested partly as potential energy viz. rise in tide level and partly as Kinetic energy viz. velocity of
flow. The formal causes the tidal flow up the rivers and the latter determines its power of transporting
silt. As the velocity of tide when it enters the mouths of these tidal rivers is high and as there is a vast
reservoir of unconsolidated silt in suspension along the delta-face, the tide as it flows up these rivers,
is highly charged with silt. The duration of Ebb tide in a tidal river is much longer than that of the flow
tide in upper reach. Hence the average velocity of Ebb is less than that of the flow. Thus the Ebb tide
is unable to transport back fully the silt carried by flow tide. Even a slight deposition of the silt will go
on accumulating as the tides function twice daily through out the year. Thus the tide channels
perform the most important function of raising the delta up to highest tide level and made fit for
human habitation unless there is human interference. If the tidal channels and creeks are allowed to
perform their above responsibility of raising land to optimum elevation the drainage of the land thus

2.22
formed does not pose so much of an acute problem.
Water flows into the Sundarbans during rising tide as long as the water levels in the areas accessible
for the incoming tides, to wit: the rivers and the unprotected lands are lower than sea level. Like-wise
water flows to the sea as long as the water in the system of waterways and unprotected areas is
higher than sea level.
The volume of water that flows into the estuary of a river and on the inundated land is that held
between high water and low water levels. The volume of this layer is usually indicated as the "live
storage" of the system. The "dead storage" is the volume of water that remains in the rivers and
creeks at the end of ebb period.
When water starts flowing in, the volume of water indicated as the dead storage is pushed inwards.
This water will fill in the live storage situated at the land side of the estuary. Fresher water from the
sea mixes with older water from the dead storage, but this process takes only place in a limited zone.
As a result of which, the water at the far end of the system is replaced only very slowly by new water
from the sea. A large portion of water moves oscillates within the rivers, without leaving the estuary.
The larger the dead storage is in comparison with the live storage, the larger the volume that remains
in the system for series of tides. This is of importance for the process of erosion and sedimentation in
the Sundarban.
The shape of the volumes of the creeks, channels and the tidal flats of the Sundarbans, providing the
live and the dead storage is very irregular. These may be thought of as a series of reservoir sections
connected to each other through channels. These channels, of course, also contribute to the storage.
The larger the live storage of any section to be filled through one or more canals, the more water is
flowing in and out through these canals with each tide.
When the live storage is reduced because of sedimentation or because of human interventions like
blocking creeks or building embankments around areas presently inundated, less water needs to flow
to and fro in the river sections feeding this part of the reservoir. When the dead storage of a river is
reduced by sedimentation, the wetted area will also be reduced and consequently the current in
these rivers needs to increase to allow the same volume of water to pass. In general it can be stated
that a reduction of the live storage will reduce the incoming and outgoing volumes and that reduction
of the dead storage increases the velocities.

2.23
2.4.10. Flora and fauna
The Natural Forest Resources consists of the mangrove forests which constitute a major resource in
terms of the area, density and diversity of mangrove species they contain. In this Division the forest
area consists of many low flat island called locally as "Char Land' and mud banks separated by a
network of anastomotic channels and rivers, the courses of which are very much prone to frequent
alteration. There is a dynamic state of erosion in some areas and creation of new mud banks and
char land in others.
The vegetative colonisation of newly formed land follows the pattern of natural succession. At first,
pioneer species establish on the site. In the case of mangroves, the seeds of these species are
dispersed by water, floating in on the high tides and lodging in the soft mud as the tide recedes.
Species of Avicennia, Rhizophora, and Sonneratia are the typical mangrove pioneers. These
pioneers are adapted to the diurnal inundation by the tides, and in fact, depend upon it. As they grow
they induce further sedimentation by reducing the velocity of water flowing past and trapping silt. As
the sedimentation build up and the duration and frequency of inundation reduces, other species like
Bruguieria, Xylocarpus, Exoecaria etc, are established. Like other natural forest succession, the
pioneers are comparatively faster growing but shorter living than species coming later ion the
sucession.
Where the accretion of the sediment reaches a level where the tidal inundation is rare, the vigor and
regenerative capacity of the mangrove species fade away. These types of land tend to become
dominated by a low thicket palm like Phoenix paludosa. Besides the frequency and duration of tidal
inundation, salinity level plays a major role in influencing the occurrence of mangrove species. As a
result of change in salinity profile the occurrence of species like Sundari (Heritiera fomes) has
become less since it is sensitive to change in salinity level.
With the progress of reclamation in the Sundarbans and increase in human population, the wild life is
faced with gradual extinction. The most noted species are Royal Tiger, Cheetal (Spooted dear) and
the Crocodiles. In Sundarbans tigers very often carry away wood-cutters, honey collectors and others
from the forest area. They are great swimmers and there are instances that they carry away men
from boats anchored in mid stream. The crocodiles in Sundarbans known as Estuarine Crocodiles
(Crocodilus Porosus) are also man eater.

2.24
2.4.11. Forest composition
The vegetation is peculiar to tidal swamps influenced primarily by salinity of water and secondarily by
the nature of soil, tides & activities of the human agency.
All the rivers in this forest tract are saline through out the year. The regions which are less saline may
be included in the Salt Water Heritiera Forest type. Not only is Sundari found in these regions but
also is the growth of vegetation much better than that in the region which is more saline. The latter
may be included in the "Low Mangrove Forest" type, here Sundari is practically absent and the
growth of the crop is extremely poor. The entire crop available in this Division (24-Parganas South
Division) is very much poorer in comparison to that of Bangladesh.
Salt water Heritiera Forest type
The upper story is composed mainly of Genwa with sattered Passur, Dhudal & Sundri. Genwa is
finally associated with a dense growth in the understroyed. Sundari is found in the northern part of
the forests, but its number decreases towards the west & south. Keora & baen are often found
occupying the mud blanks of rivers & canals. Garan, kankra & Ora are not uncommon on the river
blanks. Baen sometimes occurs almost pure. Khalasi grows as bushes only on the edges of river &
khals. The blank areas occupying the interior of the islands are either bare or occupied by very
scattered dwarf jhamti Goran, Baen and Horgoza. Pure patches of Hental are common on the dry
elevated blanks of river and creeks. Golpata prefers the ever most mud blanks and is confined to a
few blocks only, the new chars are covered mainly with Baen. The general height is 20-35 feet. The
tallest tree in the type is keora which attains a maximum height of about feet.
Low Mangrove Forest type
The composition of this type is identical with that of the preceding except Sundari and Golpata that
are almost absent and the height, growht and density are much lower.
The formation of new chars and islands is common in this region. Dhani grass appears first upon the
newly formed chars and nurses Baen, which is second in succession. When Baen is established
Genwa comes in gradually and it is only when Genwa attains a sufficient height, Goran comes as an
understorey. Ora & other species come in the intermediate period. The extreme salinity of water in
the region does not permit Sundari and Golpata to grow.
Thatch grass (ulu) is found growing in the Haliday Island and some similar islands only.

2.25
2.4.12. Colonization of the Sunderbans
Previously the entire area of Sundarbans was under forest. During the middle of Eighteenth century
when the 24-Parganas District was given to lease to the East India Company, almost the entire area
south of Calcutta was in a wild and uncultivated State with exception of small pockets of high land
bordering the Hooghly and Jamuna, once branches of the Ganga. Those areas were either swampy
or under the coverage of Forest and Jungle. The ground level was lower than the high tide level.
Being attracted by the fertility of the soil and close proximity of Calcutta some adventurous people
under the patronage of the then Collector General of East India Company, C. Rusell, started
cultivation in 1770 in Matla and Bidyadhari basin east of Calcutta. The cultivation was done by
constructing circuit embankments above tide level all along the deltaic channel to prevent saline
inundation and clearing forests and jungles within the protected zone. The drainage was done either
by Payna Cut of the embankment during low tides or by improvised type of wooden box sluices. In
1831 after the completion of survey of the Sundarbans area by Messres William Dampier
Commissioner and Lient Alexander Hodges, Surveyor of the Surevey of India the forest lands in
Sundarbans were given to settlers systematically on lease under Grant Rules 1830. This has
hastened the colonisation of Sundarbans by premature reclamation in wide areas spreading from
North Eastern boundary in Haroa, Minakhan-Srindeskhali area to Kakdwip, Sagar Patharpratima
area in South Western boundary. This method of land reclamation prematurely had not been without
its evils. On account of the embankments silt laden water at flow tide has been prevent from spilling
of over the land on either wide. The level of the land has remained low while the bed level of the river
has been raised due to deposition of silt. Rivers are choked and cease to function efficiently as
drainage and navigation channels.
The silt carried by the flow tide unable to spread over the land is being deposited in the channel bed
and is gradually aggrading it. A tidal channel when obstructed gets chocked in its own bed without
any chance of diversion by avulsion, as the energy required for the purpose is lacking, it not being
possible for a tidal channel to rise above the tide level. Thus the beneficiary activity of raising this
portion of the delta has been lost to the country and the land remains low with aggradation of
channel. The deterioration of the tidal channels has aggravated due to the absence of perennial
upland supply which could have clushed back aggravated the silt load deposited on the channel bed
during the semi-diurnal tide cycles back into the sea. No material contribution can be expected from
local drainage only during three monsoon months. The first interference was the premature
reclamation of the land on either bank of the Matla and the Bidyadhari. Boundary channels began to
deteriorate with the progressive rise in tide level of what may be called the "Heaping up tides". At port

2.26
Canning (Bidyadhari Outfall into the Matla) the highest water level has risen by 2.0 Meter (6.55 ft.) in
65 years from 1865 to 1930. Thus all the tidal channels and creeks within the prematurely reclaimed
zones of Sundarbans were, and still are, in the process of such deterioration that the problem of
drainage of the area is becoming more and more acute with the passage of time.
With the rise in river beds, there is a corresponding rise in the level of flood at flow tide require
constant raising of embankments. These evils attracted the attention of the then Government in 1909
particularly after the observance of death of Bidyadhari causing abandonment of Calcutta
Corporation drainage outfall. Two following remedies were considered:
1. Certain areas already reclaimed should be restored to tidal spill.
2. Tidal spill should not be excluded by embankments on any land in future until it has been
raised to spill level.
The first proposal was abandoned for obvious reasons of rehabilitation of displaced people and loss
of crop.
An order was issued that the tidal spill should not excluded by embankments from any land in future
until it been raised to the level of the mean of high water spring and neap tides. Since that time the
reclamation of further area has been practically stopped.
As per terms of leases of those reclaimed lands 1879 the maintenance of embankments which is the
most vital element in cultivation was the responsibility of Zamindar or Lotdars. After the Estate
acquisition in 1955-56 maintenance of these embankments in Sundarbans was vested on the
Government in the Land and Land Utilisation Department. Till 1960 the Collector, 24-Parganas
arranged to maintain these embankments, For want of technical organisation under the Collector, the
maintenance of these embankments with sluice Bridges was taken up by the Irrigation and
Waterways Development of Govt. of West Bengal.
As per Estates acquisition Act of 1955 now all the cultivating tenants have become the actual owners
of soil directly under the State up to ceiling fixed by Act.
2.4.13. Agriculture
The soils of the area are now alluvium made up mainly from washings of the Himalays by the Ganga
and its tributaries. The soil is mainly clayey (Matial) and is of great natural fertility on which winter
Aman rice of "Patiang" variety is grown. Sir William Willcocks, the internationally reputed river
Engineer who visited the area in 1928 at the request of the Government of India remarked that the

2.27
soil in Gangetic Delta is larger than that of Nile Delta in Egypt. The yield of paddy in the Sundarbans
is higher then the average yield elsewhere in the state. It has been reported on the Census Report of
West Bengal of 1951 that the crop cutting experiments, in that area at that time, indicate 16.6 quintals
per Hectare (18 meter per Acre) by traditional methods. Ninety six percent of cropped area of
Sundarbans is under Aman Paddy (winter paddy) which is practicably the only crop. The small area
on which other crops are grown consists of patches of comparatively high land. The more important
of these other crops are pulses, mainly Khesarit Jute, tobacco and vegetables. A small area is also
under orchards. The problem of Agriculture in this area is intimately connected with the problem of
drainage. The Aman Paddy is transplanted in July and harvested in December, and if the fields are
not fully drained before the harvesting time, there is huge loss of paddy due to the accumulated
water. Due to deterioration of tidal rivers and creeks for cutting spill areas the drainage has become
acute with passing of time, hence in most of the years the production falls below on account of
inadequate drainage facilities. In years of heavy rainfall the damages are more.
There is no scope of surface irrigation as the winter in the adjoining rivers and creeks are saline. A
sweet water stratum is not generally available in underground within a distance of 300m from the
surface. Hence lift Irrigation from underground at reasonable cost is not possible. Thus the area is
single cropped. Unless the area is protected by marginal embankments from saline inundation and
sufficient drainage sluices are constructed there can not be any agriculture.
The people of this region are intelligent and hardworking. They will adopt modern methods of
agriculture and increase their inputs i.e., fertiliser good seeds, pesticides etc. if they are assured of
protection from saline inundation and proper drainage.
2.4.14. Statistics of the Sunderbans (the portion that is in West Bengal)
The following data has been obtained from Jana (2005) which is of importance to this project.
Total area
Location
9630 sq. km.
On the east – River Ichhamati
On the west – River Hooghly
On the north – Dampier-Hodges line
On the south – Bay of Bengal

2.28
Administrative information
Population
Covers part of two districts – North 24 parganas (6 Developm
Blocks) and South 24 parganas (13 Development Blocks). Cont
5 Sub-divisions, 19 Police Stations, 190 Gram Panchayats
1064 villages
37,55,924 (according to 2001 census)
Islands Total - 102
Habitated - 54
Roads
6695 kms. – unmetalled
1884 kms. – metalled
Wildlife sanctuary
Sajnekhali sanctuary – 362 sq. km.
Lothian Islands sanctuary – 38 sq. km.
Halliday Islands sanctuary – 6 sq. km.
Sundarban Tiger Project
Sundarban National Park
Important rivers
Mangrove
Predominant occupations
2600 sq. km.
1300 sq. km.
Hooghly, Bidyadhari, Ichhamati, Jamuna, Saraswati, Kod
Raimangal, Bidya, Thakuran, Herodanga, Hogol, Gos
Muriganga
Mangrove species and similar vegetation – 64 types
Owners of agricultural lands, agricultural labourers, Collectio
prawn seeds, Fishing in the estuaries
2.4.15. Sunderban enviro-scapes
As such, Sundarbans has a long history geologically and ecologically. However, the relatively recent
incursion of human intervention over the past 200 years or so has made this place environmentally
fragile. This becomes especially important with the issue of survival of the people who dwell here in
spite of all odds against natural events. The rising water levels in the tidal channels has to be fended

2.29
off by raising embankments, agriculture has to be done by keeping off brackish water from entering
the fields, communication between different disjointed landmasses has to be done mostly by ferries
and boats as bridges crossing over the tidal creeks are only on important routes. Nevertheless,
certain areas have been developed to a good extent, which has given alternate means of livelihood
to the people of the area. For example fisheries as an occupation have been taken up by many and
is next to agriculture. Tourism at some places is being promoted. Nevertheless, for most of the areas
here, the question of survival at the time of disasters like cyclones still looms large. Since the rise of
the water levels in the rivers would expectedly be more, the embankments need to be raised and
strengthened. They need to be protected, wherever possible, by mangrove plantations. Connectivity
of communication routes need to be ascertained. Refuges need to be constructed at critical places
for the people to take shelter at the time of a disaster. In order to find a solution to these aspects, a
first hand understanding is necessary for the existing conditions. The images provided in the
following pages provide a glimpse of the some of the regions and their conditions.
Crossing over to Sagar islands at Hardwood Point
Dwellings close to embankments
Pitched embankments at Hardwood Point
Embankment damaged due to wave action

2.30
Mangrove plantation beyond the embankment
A retired embankment at Kakdwip
Mangrove plantation beyond the embankment
Crossing over to Namkhana
Ferry for crossing vehicles
An arduous wait for ambulance with patient at jetty
Vehicles to cross only when craft is full
Bridge across a small tidal creek (Namkhana)
Greenery protected by embankments (in the background)

2.31
Tidal creek used as berthing place by fishing boats
Fishing farms (near Bak-khali)
Mangrove plantation at Bak-khali back-swamp
Casurina plantation at Bak-khali beach
Common peoples’ ferry for crossing over to Pathar Pratima
Government Launches
Fisheries at Minakhan
Embankments across Kultigong (river at low tide)

2.32
A retired embankment of river Matla (opposite to Canning)
Mangrove plantation between embankment and the river
From over the bridge connecting Basanti
Ferries still being used for crossing people
Embankment serving as road (tide water to right)
Tidal creek used as shelter for fishing boats (Jhar-khali)
Brick paved road over embankment at Jhar-khali
Sundarban forest buffer area across the creek (view from Jhar-khali)

2.33
A couple of mangrove species at Jhar-khali eco-park
A couple of mangrove species at Jhar-khali eco-park
2.5. The western coastal zone
According to Paul (2002), the inner boundaries of the coastal plains of Midnapore littoral tract (Kanthi
coastal plains) represents this region. Along the dune and beach plain coast (Rasulpur-Subarnarekha
complex), the last line of inland dune ridge some 10 km to the north of the north of the present day
shoreline is fronted by a depositional plain covered with parallel trending sandy ridges interspersed
with narrow tidal basins of muddy deposits.
Figure 2-7. The western coastal region of West Bengal showing the different embankments
(along the rivers and the sea dyke along the sea-face (from Paul, 2002)

2.34
The beaches are flattened by storm attacks and associated wave related phenomenon. The sandy
coast of Midnapore littoral tract possesses a complicated sediment regime because of the southwest
to northeast longshore drift which transports a big quantity of sand every year. This is proved by the
recorded data of Bhandari and Das (1993), which estimates an average of 100000 – 128000 m 3 per
year across different sections at old Digha beach. This sediment interacts with the downstream
discharge of the Hooghly estuarine sediments which in turn produce a circulation path of sediment
transport and modify the coastal topography along this region.
In this region, the sandy beaches are predominant, and according to Chakrabarti (2004) here the
erosion is present in the beach face of Digha-Shankarpur (Chandpur) sectors whereas accretional
phenomenon is observed in the same beach face of Dadanpatrabar-Junput area. This has been
shown in Figure 2-8. The sea face here is constantly under the threat of erosion by the impact of
ocean waves, and the higher waves lashing the shore during storm surges generated by cyclones
are of serious concern to the stability of the beaches and shoreline. There has been indiscriminate
human action leading to destabilization of the coastal zones over the past couple of decades.
Figure 2-8. The geological and morphological features of the western coastline of West Bengal
(from Chakrabarti, 2005)

2.35
This has led to the Government to the promulgation of the Coastal Regulatory Zones (CRZs). For the
Digha Development Area, falling under the western coastal plains of West Bengal, the sectors A-1,
B-5, F-1, F-2, H-1 & N are categorised as CRZ-III. The sectors B-1, B-2, B-3, B-4, B-7, C-5, E & E-3
are categorised as CRZ-II. In case of Haldia Development Area, also located in the western coastal
plains, the Haldia Port Complex Area only is categorised as CRZ-II. The CRZ for Haldia shall be
100m from the High Tide Line. For the Digha/Shankarpur area, the portion up to sand dunes has
been classified as CRZ-I and area beyond dunes.
There is a small stretch of sea beach to the west of Digha extending up to the West Bengal-Orissa
border, which is a part of the Subarnarekha estuary. The character of this part of the coast is similar
to that from Digha to Junput.
2.5.1. Physical features
Paul (2002) mentions that there are seven sets of beach ridges in the Subarnarekha estuary, which
is in the Balasore district of Orissa, but just a few tens of kilometers along the coast from the Bengal
border. Each set of beach ridge is followed by a number of bars. These are linear to slightly curved
beach ridge features which are also extended towards the Kanthi coastal plains of the east
Midnapore district, but the number of beach ridges followed by bars is reduced in the coastal
tract.marine terraces are present all along the Digha shoreline of the east Midnapore district. The
ancient dune ridge complex of Kanthi-Paniparul region is thought to be formed by the marine
regression. The dune sands are oxidised and the dune ridge indicates the position of the ancient
shoreline of kanthi coastal plain.
2.5.2. Topography
The western coastal plain of West Bengal is represented by the strandplain surfaces of Kanthi and
Digha. Slow upheaval of the region and successive shoreline regression during the Holocene
(geologic) period has left a significant topographic impression of ancient marine features. Series of
beach ridges, bars and older dune ridges or younger dunes, tidal basins of the past and marine
terraces reveal the typical raised features of this coast. All the linear features are parallel to the
present day shoreline. Older sand dune sediments of Kanthi, Darua-Paniparul-dariapur-Khajuri
regions are oxidised and rain washed over a prolonged period. By height and the largest area of
occupation, the dune row represents first shoreline of strandplain surface and longer phase of the
regressive sea. The eastward extension of the Ramnagar beach ridges is restricted by the presence

2.36
of a doiminant tidalbasin of the Holocene period around the region (Paul 2002). Surface height of the
beach ridges range from 3.5m to 4.6m above the sea level. Two or three rows of closed spacing
dunes separated by linear tidal valleys, represent the Digha surface of the the present day
shoreline.The two successive sand dunes are lying over the two significant terraces from the
shoreline to the inland location around Digha. The beach fringed dune row is continuous laong the
present shoreline of Digha, Shankarpur, Dadanpatrabar, Junput, Dariapur and Khajurri sectors.
Younger dunes, because of their active depositional process along the beach fringed shores, are
higher in altitude than the older ones. This dune row, though, is affected by toe erosion and wave cut
cliffs all along the shoreline from Digha to Dadanpatrabar areas. In between Ramnagar beach ridges
and Digha dune row, shore parallel salt marshes are extensive around the mouths of the Digha
estuary, Jaldah estuary and Pichhabani channel. They are also the tidal spill basins of monsoonal
high seas (Usually flooded from June to November) around the region.
Specific regions may be identified for dune ridge colonies along the western coastal plains of West
Bengal. The longest beach-fringed dune ridge sector of the Kanthi coastal palins runs along a stretch
of 19.5km shoreline from Pichhabani tidal pass to Rasulpur river. This low-height (3.3m to 6.0m) and
widespread dune sector (180m to 300m) of Junput region is covered partially by planted casurina
forest. Over a kilometer wide beach plain dominated by fine sand and silts, and associated seafront
tidal flat surface provide a mixed and complex sub-environments of idff energy levels for the growth
of Aeolian sand dunes and widespread estuarine or tidal flat deposits around the shoreline of Junput.
The northeastern part of the Kanthi coastal plain comprises of extensive low-lying tract of fluviomarine
deposits. The entire alluvial tract has evolved through the seaward advancement of delta fan
deposits of Rupnarayan and Kasai rivers at Holocene regressive phases of the sea (6000 YBP).
Estuarine tidal flat deposits are sre still active around the channel margins, channel beds and
unprotected tidal spill basins. The regions of Khajuri, Hijli, Nandigram, haldia, Sutahata, mahisadal,
and Tamluk have elevation ranging from about 2m to 2.4m above mean sea level. The lowland
surface is dissected by several tidal channels, Hijli tidal canal, Rasulpur, Haldi and Rupnarayan
estuaries. The land elevation of the floodplains and tidal flats of these rivers are expected to increase
concurrently with the sea levels as fresh alluvium continues to be deposited, except where this is
prevented by coastal embankments. At the same time, the raising if the embankments have further
impeded drainage from interior floodplain areas of Kasai and Rupnarayan.
Compared to an open shoreline of Digha, the barred coasts of Talsari and Junput, where an
emergent offshore sand bar or sand spit creates a more or less enclosed lagoon, have a more

2.37
comlex geometry, and a range of energy levels in depositional processes. The enclosed lagoons of
Talsari and Junput accumulate sediments that are identical to either estuarie or tidal flat deposits.
2.5.3. Rainfall, Temperature and Humidity
As such, the rainfall, temperature, wind and cyclone characteristics are somewhat similar to that
described for the eastern coastal zone. However, the long dry spell of hot humid summer brings a
drastic change in the dune formations and sand hazards. At this time the summer temperature
ranges from 29 0 C to 38 0 C. Sand surface temperature of the bare sand dunes rises up to 48 0 C around
the month of May. Rainfall is comparatively lower in the western coastal tracts (of east Miidnapore
district) than the eastern part (south 24 Parganas district). September is the rainiest month. Number
of rainy days ranges from 100 to 150 though it varies from year to year in the littoral tracts. The
amount of rainfall also fluctuates from year to year duw to the dominance of landwinds over maritime
influences. In the year 1986, the rainfall recorded at Digha was 2066.5mm compared to 258.3mm in
1985. The average humidity is just over 80 percent and is more or less uniform throughout the year.
2.5.4. Winds
The normal wind record of Sagar, Sandheads, Digha and Kanthi stations reveal that the prevailing
wind blows from north and northeast from the beginning of October to the middle of march. The
months of January and February are relatively calm.Violemnt winds start blowing again from about
the middle of March till about the end of September. The average wind speed during the southwest
monsoon varies from 30 to 50 km per hour. Storms are common during spring and autumn when the
wind velocity generally exceeds 100 km per hour. In the winter months, the wind speeds generally fall
below 10 km per hour all along the coastline.
2.5.6. Sediment/Soil characteristics
Both cohesive as well as cohesionless soils are found along the coasts of the western littoral plains.
Cohesionless soils (for example, sand) are made up of solid grains usually bigger than 0.06mm in
diameter. According to Paul (2002) over 90 percent of the coastal sediments of West Bengal are the
products of rivers. Graphical presentation of sediments of the western coastal plains, especially near
Digha beach fce shows weak bimodal size. In the dunes, estuarine banks and beach samples, the

2.38
primary mode is centered on the fine grained sand. The same reference cites the following mean
sediment sizes for the coasts:
Region
Mean diameter (mm)
Coastal foredunes
Coastal inland dunes
Sea beaches
Digha dune sand 1.44 to 2.80
Dariapur dune sand 2.15 to 2.95
Kanthi dune sand 1.58 to 2.25
Paniparul dune sand 1.98 to 2.00
Junput beach sand 2.57 to 2.70
Digha beach sand 1.83 to 2.80
2.5.7. River system
The rivers Hooghly, Damodar, Rupnarayan, and Haldi rivers with their freshwater discharge and
sediments have led to the deposition of terrigenous sands, silts and clays to form deltas. Damodar,
Rupnarayan, and Haldi rivers have built their deltas over the shallow offshore flat of the geological
past in east and southeastward direction. Further eastward advancement of the deltas was cheked
by the southward trend of delta building activities of Bhagirathi-Hooghly river in the Bengal Basin.
The Kanthi strandplain surface is produced by composite river and wave dominated forces.
2.5.8. Tides
The Digha coast experiences semi-diurnal tidal fluctuations. During autumnal equinox the tidal
amplitude ranges from 5m to 5.8m from the mean sea level. The general tide level of this area,
however, is 4.5m above the mean sea level. Tidal ranges in excess of 4m produce strong tidal and
residual currents which may extend for hundreds of kilometers inland. The river Hooghly is affected
by the tidal fluctuation upto about 300km inland (up to Nabadwip). Changes in winds and
atmospheric pressure can thus cause the actual tidal level to be very different from the expected
value, especially during storms. The heay rainfall associated with cyclonic storm in the gangetic West
Bengal produces enormous discharge of freshwater in the river Hooghly when met with a rising storm
surge may cause huge inundation as happened in the last week of August and first week of
September 1978.

2.39
2.5.9 Western coast visuals
Boulder pitched anti-erosion bank revetment at New Digha (looking
east)
Boulder pitched anti-erosion bank revetment at New Digha (looking
west) – Casurina shelter belt plantations in the background is in
Orissa
Young Casurina shelter belt plantations at New Digha
Concrete block pitched revetment (for about 1 km) at Old Digha
Beach erosion with affected Casurina plantation east of Old Digha.
Temporary protection erected to prevent further erosion
Beach erosion and affected Casurina plantation at Shankarpur.
Damaged approach to sea being temporarily protected.

2.40
Aquaculture ponds located between sea dikes near Digha
Earthen Sea dike along the approach road from Contai to Digha
Sea bank erosion along Chandpur beach
Temporary protection of sea bank from wave dash along Chandpur
coastline
Depletion of shelterbelt plantation along Chandpur coastline
Flooding near Belda (East Midnapore) as a result of excessive
precipitation due to cyclonic depression
Shelter less people taking refuge along elevated Highways (near
Belda)
Inundation of agricultural land near Egra (East Midnapore)

2.41
2.6. The Hooghly estuarine islands
As may be seen from figure 2-9, the river Hooghly estuary is situated in between the western littoral
tracts and the eastern Sundarban region of the West Bengal delta. River Hooghly is the largest fresh
water discharge carrier as it gets water from many rivers that contribute their flows to it. There are a
few islands within the estuary of Hooghly which are inhabited, the largest and most famous of these
being the Sagar Island. It is also the largest of all the islands – around 209 sq. kms.
Figure 2-9. Important islands at river Hooghly estuary
Many linear sand banks parallel to the tidal flow s have elevated the flood of the Hooghly estuary,
which have some places developed into islands. Accumulation of finer sediments is enhanced with
the colonization of salt marsh plants and mangroves on the island surface. However, these islands
are intersected by many tidal creeks which convey the tide waters into the middle part of the island
during tidal flooding. Catastrophes like cyclones and associated storm surges, tidal waves, disastrous
floods destabilize the growth of islands in the estuary.

2.42
All the islands are situated within the middle reaches of the Hooghly estuary. Some of these are:
nayachara, Ghoramara, Lohachara, Bedford, Sagar, Sikarpur, Kankramari, Mahisani, Jambu, and
Chuksar. Lohachara and Khasimara islands are already eroded in the estuarine environment.
Ghoramara and Bedford islands are gradually being reduced in their size. Parts of Sagar Island
(Bisalakshipur, Beguakhali, and Sikarpur) are also eroded by faster tidal currents (Paul 2002).
The 11.5km long stretches of the sea front of the Sagar Island on its southwestern side, parts of the
Jambu Island, and the seaward side of the Chuksar Island are dominated by shoreline features and
backshore dune fields. Waves and currents deposit sand in the shore zone of open sea-facing
islands of the Hooghly estuary. Strong onshore winds, particularly in the pre-monsoon season,
transport sand from the sea beach to the back-shore areas where dense vegetation cover attracts
sand particles to accumulate into sand dunes. Dunes are less frequent weher abundant sand supply
is absent (Paul 1994).
The most extensive landforms found in the Hooghly estuary channels are the tidal flats, which are
mostly restricted to intertidal zone. Tidal flats occur in the sloping sides of estuary channel and minor
tidal channel, and also on the island and bar surface. According to Paul (2002), there are two types
of tidal flats in the Hooghly estuary – the sheltered flat and the open-sea tidal flat. Variation of wave
heights and tidal ranges controls the geomorphic positions and morphologies of the tidal flats.
Islands, bars, and deltaic flats of the inland estuarine section are usually sheltered from the effects of
wind-driven waves. The sheltered section of the estuary with large tidal range enhances the
deposition of fine-grained silts and clays to form mud flats and marshes in the islands and deltaic
flats. Nayachara Island, Bedford Island, Sikarpur Island and Kankramari Char are good examples of
such extensive growth of tidal flats.
The shorelines of Sagar Island, Jambu Island, Chuksar Island, Frasergunj, and Bak-khali are
exposed to wave attacks at the lower reaches of the Hooghly estuary. Here, the accumulation of
sediment deposited by waves and currents has produced beaches in the shore zone.
The human habitation within the islands is guarded by circuit embankments, which act more like
polders. Some of the embankments (like those in Sagar Island) are looked after by the Kolkata Port
Trust (KoPT), and the rest by the Irrigation and Waterways Department (I&WD) of the Government of
West Bengal. However, the retired embankments (the embankment that is situated some distance
away from the riverbank) are less prone to damages which can be severe due to the cyclinic strom
surges. KoPT has prepared a scheme for river training works in the interior of the estuary on the
basis of recommendations of various expert committees and on the basis of the results of Hydraulic

2.43
model studies carried out Kolkata, Pune and Hamburg (Germany). This is, of course, has been done
with the intention of maintaining the navigable channels at Kolkata and Haldia ports. The protection
measures for the Nayachara Island have been completed by the KPT under this scheme.
The rest of the embankments under the I&WD need extensive repair and protection, if the interests of
the population residing within these circuit embankments need to be protected. This is all the more
important as most of the islands face the wrath of not only the storm surge waves, but also the strong
gales associated with the cyclones.
2.7. Threat of damage from tropical cyclones
The vulnerability of the eastern coastal region of the State of West Bengal due to cyclones is due to
the two reasons: (a) Erosion of the river and creek banks of network of channels the due to strong
river currents, and (b) The damage to the embankments by the impact of the wave dashes that
generate due to cyclonic storms. These waves could be the direct waves from the oceans hitting the
embankments facing the sea. Or, these could be the waves diffused in the tidal creeks that hit the
embankments in the hinterland.
The other threat from cyclonic storms is due to the damage of infrastructure due to the excessively
strong winds. In the coastal regions of the state, the general socio-economic condition of the local
populace is rather low. Consequently, the housing types mostly belong to those made of mud,
bamboo and other locally available raw materials. The roofs of most of these kutcha houses are
made of thatch, though baked tiles are also common. However, all these are quite vulnerable to
strong gusts of wind.
The cyclonic depressions also generate a lot of precipitation. The inhabited areas of Sundarbans are
mostly enclosed by circuit embankments and hence a lot of rain results in waterlogged conditions at
the time of cyclones. According to Kanjilal (2006), proper field drainage is required to bring excess
water from the farm plots and the village area to the main drainage canals and to keep the ground
water level sufficiently low. The slope required for the transport of this excess water needs to be in
line with the available head determined by the difference in level of the farm plots and the water
surface in the main canal to which the excess water needs to be evacuated. The system of canals
and ponds which is supposed to:
• Collect and to store the water to be used later for agricultural or domestic purposes,

2.44
• Transport the water to the sluice gates with an acceptable loss of head to allow for a
maximal head at these gates,
• To store the excess water that needs to be spilled through the sluice gates during the
periods that this drainage is hampered by high water levels in the rivers.
Well sized sluices are required to evacuate the excess water during ebb, with proper gates which,
provided that they are adequately operated and maintained, can keep the water level in the system
within acceptable limits and can prevent intrusion of saline water through the gates during high tides.
If drainage in tidal regions is not performing satisfactorily often people are inclined to assume that the
sluice gates are too small and are as often inclined to neglect the other components of the system.
An enlarged storage in the main system does not reduce directly the total amount of water that needs
to be spilled but it reduces the required capacity of the sluices be-cause the evacuation of water can
be arranged over a longer series of tides. When however the enlarged storage should lead to an
extended area to be cultivated in the dry season, the volume of water that needs to be spilled will
reduce. Excess water is "promoted" to useful water.
Without detailed information it is impossible to determine which package of measures should be
taken to establish the best possible drainage infra-structure. This does not mean that no action can
be taken to improve the present situation without a detailed investigation. An inventory mobilizing the
experiences of the farmers might lead to indications about the "bottle-necks" in the drainage process.
Nevertheless, the absence of representative climatological data and reliable topographical data about
the levels of the different plots, levels and sizes of the canals and ponds, levels of the sluices and
data about the water levels in the rivers is a constraint for the implementation of the best possible
drainage system.
2.7.1. River / channel bank erosion
As mentioned before, the banks fail due to either an undercutting by strong flows in the channels
parallel to the bank or by slope failure, which may be termed as geotechnical failure. Figure 6 shows
the mode of failure and bank retreat due to parallel river current and Figure 2-10 shows the modes of
geotechnical failure.
As may be observed from Figure 2-11, there could be one mode of failure of the river bank, in which
strong river currents erode away the toe material from the bottom of the banks. In this way, the base
becomes weaker, and gradually the entire bank line recedes.

2.45
It has been mentioned earlier that most of the rivers and creeks in the Sundarban estuary do not
have any head water discharge from the upstream, meaning thereby that there is no substantial
catchment for these channels on the upstream. Thus there is no possibility of the river current
becoming very high due to a high rainfall in the catchment. The only reason why the river currents
may become high is due to a higher influx of tidal water due to a higher rise on the ocean level, which
may be possible with a storm surge activated by a cyclone. The sudden gush of water in such a case
may affect the concave banks of a river more, since the velocities would naturally be higher than the
average river velocity. Further, in a strong bend, the presence of secondary currents (in a plane
across the river flow) may also aid in undercutting the bank toe.
Figure 2-10. Bank failure and retreat due to undercutting of riverbank base by strong river
current
Figure 2-11. Bank failure modes (From Hey et al. 1995)

2.46
The other type of failure may occur due to reasons like the presence of excess pore pressure
generated by a quick falling river water level. When a bank fails in this kind of geotechnical mode, the
probable slip lines or slip circles may be predicted, which depends also upon the type of material
forming the banks.
2.7.2. Embankments/dykes and their failures
Agriculture is carried behind the nearly 3500 Kilometer of protective earthen embankments. Those
are constructed by local earth of surface layers which consist mostly of very fine coherent. It is
generally of low liquid limit. This soil has got the property of low erosion resistance because this
material becomes liquid in coming with contact with water. Previously a forest belt of minimum width
of 100 meter was kept as Foreshore land in aligning on the embankment for the purpose of damping
the wave action. But by this time the increase of population and want of fuel has caused unregulated
felling and now practically there is no protection to embankment from high waves and suiting
currents.
These dykes were originally constructed by the Latdars with the gradual rise of high water level over
the years; the Latdars increased the height of the dykes correspondingly. The constant erosion of the
soil due to wave wash was also attended by them. But since late forties of this century the Latdars
started neglecting the maintenance due to rise in labour cost as well as the apprehension of
imminent state purchase of the Latdar's interest. The dykes at the time of taking over by the Irrigation
Department in 1960 were found to have inadequate section and strength. Breaches and overtopping
was of quite common phenomenon.
Due to paucity of funds, this enormous length of embankments could not furthermore be brought to
adequate section and height to ensure safety. In many cases these dykes are aligned bordering the
scouring bank of meandering rivers. This necessitated another set of embankments, some dist
inland, called the retiring embankments.
Generally during flow tide accompanied strong southerly wind from second fortnight, of March, to
October, the river water splashes over the earthen embankment causing continuous erosion of soil.
This phenomenon occurs twice a day and the poor soil give very little resistance to it. On an average
two major tropical cyclonic storms occur in each year in Sundarbans. During such cyclone storms
high waves are generated in sea face and which attack on the embankments at great storm velocities
and thus overtop embankment without free board, erode river side slope and crest and cause breach.
For want of cover protection works (Brick or Brick Block Revetment works) in strength of vulnerable
zone, the breach cannot be prevented.

2.47
As such, since most of the embankments have been constructed by many years before by not so
scientific methods, the failures of these is no surprise, especially if these do not have adequate
gradient on the river side or on the land side. Further, even if these are well constructed, the gradual
undercutting of the riverbank may lead to weakening of the foundation of these embankments leading
to a sudden collapse. If the embankments do not have adequate face pitching, there is a high chance
of these getting eroded away by the impact of lashing waves generated in the ocean or the rivers due
to cyclonic storms (Figure 2-12).
Figure 2-12. Embankment failure due to wave dash
It may also be possible that the embankment protection in the form of brick pitching may not be
strong enough at places to bear the wave dash, leading to exposure of the river side bank and
consequent erosion.
A study by Hazra (2006) comparing the earlier maps of the Sundarbans and present day satellite
imageries has inferred important statistics about the vulnerability of the islands in the region due to
cyclonic effects. The researcher and his team had calculated the length of the embankments from
Survey of India Topographic sheets (No.79B/4, 79B/8, 79B11, 79B/12,79B/ 16, 79C/1, 79C/2, 79C/5,
79C/6, 79C/9, 79C/10, 79C/13, 79C/14, of 1969). The embankments were then digitized and length
calculated, which was found to be around 3110.33 Km. Comparing this with the recent IRS 1D LISS
III and PAN data of 2001, it was found out that some parts of the embankments have already been
washed out by cyclones and erosion. It has also been inferred that due to high rate of siltation on the

2.48
channel floor, some of the rivers like Muriganga, encircling the populated islands, are flowing above
the level of the coasts. Detailed statistics has been provided in Table 2-6.
Table 2-6. Change in area of the estuarine island system of Sundarbans
(From Hazra, 2006)
Islands
Area in sq.
Area in sq.
Area loss
Status of Embankment
kms (1969)
kms (2001)
in %
Dakshin
52.722 44.520 15.55 125Km, 40 Km vulnerable
Surendranagar
Sagar 253.203 241.042 4.80 250Kmlong embankment, 15
km washed off, 90 Km
vulnerable
Namkhana 156.908 149.222 4.88 150 Km. long embankment 50
Km vulnerable
Moushuni 35.244 30.067 14.60 30 Km long embankment 15
Km vulnerable
Lothian 36.041 34.986 2.92 Mangrove forest: No
embankments
Jharkhali 162.00 161.328 Stable 150km long embankment
Ghoramara 9.083 5.349 41.11 5 Km Washed off
Dulibhasani 190.515 185.338 2.72 Mangrove forest: No
embankments
Dhanchi 39.041 34.174 12.46 Mangrove forest: No
embankments
Dalhousie 78.233 66.713 14.73 Mangrove forest: No
embankments
Bulchery 32.700 26.227 19.80 Mangrove forest: No
embankments
Ajmalmari West 25.189 25.096 0.37 Mangrove forest: No
embankments

2.49
Ajmalmari East 75.664 70.923 6.27 Mangrove forest: No
embankments
Bhangaduni 45.112 30.855 31.6 Mangrove forest: No
embankments
Jambudwip 17.543 5.519 68.54 Mangrove forest: No
embankments
Further important observations regarding the erosion accretion pattern of the island system, as
inferred by Hazra (2006) can be summarised as follows:
• Erosional zones are most prominent among the 12 sea facing southern islands including
Sagar at the west to Bhangaduni in the east.
• Few islands, like Lohachara and Bedford (6.212 Km2), have already vanished from the map.
• Within the inhabited islands, Ghoramara & Sagar and Mousuni Island together have suffered
the bulk of erosion. Jambudwip, being the southernmost island at the confluence of Hoogly,
has shown landless by 68%
• Total erosion over the 30 years time span is estimated to be 162.879Km2.
• The western banks of the island are more vulnerable than the east and the rate is more
severe indicating the role of tidal surges. Erosion is also seen along the sea facing
shorelines where it is oblique.
• Marginal accretion is localised in the inner estuary particularly along eastern and northern
margin of islands and along the coast where it is mostly E-W and sea facing. Amount of land
accretion over the past 30 years is estimated to be82.505Km2.
• Emerging mud flats of 70's have suffered the maximum loss, due to not only erosion, but
probably submergence as well.
• The eastern matured islands are found to be comparatively more stable due to the presence
of thick mangroves and lesser anthropogenic activities. Only marginal submergence is
observed.
Over the last 30 years, around 7000 people have been displaced and turned into environmental
migrants due to sea level rise, coastal erosion, cyclone and coastal flooding breaching the

2.50
embankments. Crops and properties over Rs.900 million have been destroyed and around 500
people have lost their lives. These numbers are likely to increase manifold in future.
The study also notes that the Sagar Islands is the most populated and vulnerable island of the
Hoogly estuary. Over the last few decades the island has been seen to register a land loss of 12 Km2
with marginal accretion on the portion of the southern and eastern fringe. Within the last few
decades, nearly 3800 persons have been rendered homeless from Sagar Island itself due to sea
level rise, coastal erosion and flooding due to cyclones and consequent storm surges. In addition,
four refugee colonies for the displaced persons from other islands (Lohachara, Ghoramara etc) have
been set up at Sagar. A mathematical model coupled with GIS database developed by the School of
School of Oceanographic Studies, Jadavpur University; demonstrate that with the current rate of sea
level rise, the Sagar island will loose around 15% of its existing land area by the 2020. An estimate
considering the population growth rate and future population density of Sagar indicates that the
number of displaced persons due to sea level rise and associated storm surges/coastal flooding will
be around 30,000 by 2020.
2.7.3. Inundation
As mentioned before, the problem of inundation due to high rainfall within the circuit embankments of
the inhabited islands is inevitable at the time of a high tide, coupled with a storm surge. As such,
proper drainage is required along with right kind of sluices and vents. At the time of a high sea level,
the island dwellers are also at a constant threat of further inundation likely to be caused by possible
embankment failure. Since the dwellers here have settled before the full maturity of development of
the islands, they continue to suffer from the gradual rise of the surrounding riverbeds compared to
their lands. Due to premature reclamation, the average ground level of some of the populated islands
remains between 1.55 m to 0.75mts below the mean high water level of the tides and in the coastal
area, the ground level remains about 2.60m below. This accentuates further the risk of embankment
failure and washout. These embankments have now become the lifeline of the Sundarbans islands,
as because, the safety of the lives and properties as well as agriculture and subsistence are
dependant on the stability of the embankments.
Excess rain water is drained from the fields into a system of canals and ponds. Some of the canals
and ponds are excavated by the farmers for this purpose. Others are the result of the construction of
embankments and roads. On many islands the canal system partly consists of small natural creeks in
which dams has been constructed at their downstream end. The internal system of canals and ponds

2.51
is used to store fresh water for domes-tic use and for drinking water of the animals. This fresh water
is also used to water the garden crops which are grown in the dry season.
Culvert type sluices, mostly provided with flap gates and with sliding gates enable spilling of excess
water to the tidal rivers during periods when the water levels of these rivers are lower than the water
levels in the internal drainage systems of the islands. When the water level of the rivers are higher
than in the internal system, drainage is not possible. All water that flows into the system during these
periods needs to be stored in the canals and ponds. Consequently there are two reasons water
needs to be stored in the internal system a socio-economic one and one which is of a more technical
nature.
When the sliding gates of the sluices are open water will be drained to the river as soon as the water
level in the river is lower than the water level in the internal system. The flap gates will open
automatically; at first only slightly but when the difference in water level inside and outside increases
the gates will open wider.
When during outgoing tide the water level of the river becomes lower than the water level in the
internal system and the sliding gates are open, the culvert might be in a submerged condition but
soon the river level will be lower than the top of the culvert bringing the sluice in the intermediate
condition. For other culverts in the Sundarban discharge starts under these intermediate conditions.
Near the end of the outgoing tide the sluice might enter the free flow condition but as most of the
sluices are not built close to the river often the water level in the level in the canal section connecting
the sluice with the river will remain higher than the bottom of the culvert. Due to all this the
discharges of the sluices cannot be computed but can only be determined by measurements.
The presence of the flap reduces the discharge capacity of the sluices significantly. By its weight the
flap is pushed downwards and this hampers the outflow of water. Some of the flaps in the Sundarban
are constructed of wood, others are of cast iron. Although the latter are better from a maintenance
point of view, they are heavier and reduce the outflow more than the wooden flaps.
As the formula indicates, the discharge of a given sluice gate is determined by the water head. When
the gate is spilling water the system of canals and ponds needs to convey water to this gate. For a
proper drainage it is important that this transport of water is realized with a minimum loss of head.
In theory there are two methods to reduce the loss of head in the canals:
1. To reduce the slope in the canals required to transport the volume of water that needs to be
spilled by the sluice. This can be realized by wide and smooth canals. This means that the
canals to the sluices need to be cleaned and as much as possible free of any obstacles.

2.52
2. To reduce the average distance water needs to be transported during the periods the sluice
is able to spill water. This means that the main body of the volume stored in the internal
system should be located as close as possible to the gate.
Many ponds and channel sections are used for fish breeding. Nets are used to prevent the fish to be
washed away. These nets might reduce the discharge capacity of the canals significantly when they
are stretched from one side of the canal to the other. Here is a conflict of interest.
Zoning might offer a compromise. If fish breeding can be restricted to the far end sections of the
canals or even better in special ponds, the reduction in the drainage capacity of the system might be
limited. Zoning is not necessary if the velocity of the flow in the canals of the internal system is low
(less than 0.15m/sec) when the sluices are spilling at full capacity. In any case it is advisable to avoid
nets right in front of the inflow of the sluice gate.

Chapter Three
Effect of Cyclones on Kolkata and Surroundings
3.1. Hazard on urban habitation zones due to tropical cyclones
The most important urban conglomeration within the easy reach of tropical cyclonic storms is the
State Capital Kolkata. Contiguous with Kolkata proper is a large urban area that includes what is
called the Greater Kolkata, including the relatively newly developed township of Bidhan Nagar (also
called Salt Lake) and the upcoming Rajarhat development area. Presently, the Kolkata Municipal
Corporation Area measures around 187.33 sq. km. According to the 2001 Census, the population of
this region is around 45,80,544 and the area is divided into 15 Boroughs and 141 wards. According
to historical according, Kolkata developed around three villages – Sutanuti, Kolkata, and Gobindapur.
These villages occupied the following present day regional demarcations:
CHAPTER 3
Sutanuti
Kolkata
Gobindapur
Chitpur, Baghbazar, Sobhabazar & Hatkhola
Dharmatala, Bowbazar, Simla, Janbazar
Hastings, Maidan & Bhowanipur
The newer additions to the Kolkata municipality are the following:
North
South
East
Sinthi, Cossipore & Gughudanga
Tollygunge, Khidderpore & Behala
Salt Lake , Beliaghata & Topsia
The city on the west is bound by the river Hooghly.
As such, an intense rainfall as during a tropical cyclone over this region means a lot of runoff since
much of the areas has been paved with little or no scope for natural infiltration. Ironically, the terrain
of the land slopes from the west, at the edge of the river Hooghly, towards the east. Further east are
the scattered salty marsh lands crisscrossed by the different tidal streams and channels that are
connected to the Bay of Bengal to the south. The important creeks here are the Matla, Bidyadhari,
Kultigong, Ichhamati, Raimangal, etc. Of course, a small portion of the city, mainly to the south and
closer to the river Hooghly drains to the west. However, whether the eastern tidal creeks, or the river
Hooghly to the west, both are prone to water level variations of the ocean: the Bay of Bengal, to be
precise. This rise of water levels in the rivers is due to either only tidal variations or that coupled with

3.2
a storm surge caused by a tropical cyclone. Under such a condition, when a lot of water needs to be
discharged off from the city, the outfalls are found to be blocked of by a high water level of the
creeks. This renders the city waterlogged for many hours at a stretch at times. In order to understand
the full system of Kolkata’s urban drainage and the reason for this kind of drainage congestion, it is
necessary to go back in history and review the city’s drainage system from the beginning. The
authors of this project report are grateful to Dr. S. S. Ganguly, retired Superintending Engineer,
Irrigation and Waterways Department, Government of West Bengal for permitting the use of the
following descriptions about Kolkata and its drainage proposals from the paper Ganguly (2006).
3.2 Physiography and the drainage systems planned during the formative years of Calcutta
(Kolkata)
The physiographic setting of Kolkata (22° 34' N, 88° 22' E), both at the time of its foundation as well
as in the present day, is dominated by the meandering Hooghly river. Along the left bank of the river,
which is also the western boundary of the city, there stretches a narrow belt of comparatively high
natural levee, which varies in 2 to 5 kilometers. As a consequence of this natural levee general slope
of the land was from west to west. But during the initial years, drainage of the city was directed
westwards to the Hooghly-river. A small creek, the Gobindapur creek was utilized. The creek ran
from the Salt Lakes in the east via present day Beliaghata, Sealdah, Creek Row, Dharmatolla and
Government Place (North) before draining into the Hooghly below the Princep Ghat. This creek also
served as a navigation channel and it is reported that Charnock used to collect toll from the boats
moving in and out of the creek. But in course of a furious hurricane on Sept. 30, 1737 when 15
inches (38.10 cm) of rainfall occurred in just 5 hours, 20,000 ships, barks, sloops, boats, canoes etc.
were destroyed, the creek was rendered almost useless for navigation. In 1742, a seven mile long
ditch was excavated along the present alignment of the Circular Road (APC Road & JPC Road) to
keep the Maratha marauders at bay. This ditch aptly called the Marhatta ditch sounded the death
knell of the creek. The natural and man made interferences took their tool on the not so efficient
drainage system of the city. Very soon drainage congestion resulted and prolonged water logging
was the order of the day. The consequences were so severe for the health and hygiene of the city
that then Governor General Lord Wellesley (1766 - 1842) had to intervene. His now famous minutes
of June 16, 1803, which recommended radical change in the direction of the principal channel of the
Public Drains, read as follows:
"The defects of the climate of Calcutta, during the part of the rainy season, may indeed be ascribed
to the state of the drains and water courses and to the stagnated water remaining in the Town and its

3.3
vicinity … And it is believed, that the level of the country inclines towards the salt-water lake, and
consequently that the principal channel of the Public Drains and water-courses ought to be
conducted in that direction".
Lord Wellesley's Improvement Committee better known as the Lottery Committee (1814-1836), as it
drew its sustenance from Lottery Receipts, with a view to improving the situation, undertook
extensive urban development works, by constructing roads and drains, filling up filthy tanks and
excavating new ones. Beliaghata canal still remains a useful contribution of the committee towards
Kolkata's drainage system. The Lottery Committee was disbanded in 1836 by recoil of the British
public opinion, The Fever Hospital and Municipal Improvement Committee, which succeeded the
Lottery Committee, was formed by Lord Auckland in 1836. The duty of this committee was to
deliberate on public health problems and to suggest remedial measures. The committee identified
decrepit condition and inadequacy of drainage facilities as the primary reason for the widespread
incidence of various severe diseases. From then onwards the drainage system of the city was
modified or extended to meet the emerging requirements of the fast expanding city. The rapid rise in
population brought with it fresh built up areas to contend with and to observe and take into account
important changes talking place in the natural outfall system into which the drainage of the city would
ultimately drain.
3.3. Establishment and expansion of the city
The name Kalikata had been mentioned in the rent-roll of the Mughal emperor Akbar (reigned 1556-
1605) and also in the Manasa-mangal of the Bengali poet Bipradas (1495). The history of Calcutta as
a British settlement dates from the establishment of a trading post there by Job Charnock, an agent
of the English East India Company, in 1690. Charnock had previously had disputes with officials of
the Mughal Empire at the river port of Hooghly and had been obliged to leave, after which he
attempted unsuccessfully to establish himself at other places down the river. When the Mughal
officials, not wishing to lose what they had gained from the English company's commerce, permitted
Charnock to return once more, he chose Calcutta as the seat of his operations. The river Hooghly at
this point was also wide and deep; the only disadvantage being the marshes to the east and swamps
within the area which made the spot unhealthy. Moreover, before the coming of the English, three
local villages Sutanati, Kalikata (or Kolkata), and Gobindapur, which were later to become parts of
Calcutta (mentioned at the beginning of this section) had been chosen as places to settle by Indian
merchants who had migrated from the silted-up port of Satgaon, farther upstream. The presence of

3.4
these merchants may have been to some extent responsible for Charnock's choice of the site. By
1696, when a rebellion broke out in the nearby district of Burdwan, the Mughal provincial
administration had become friendly to the growing settlement. The servants of the company, who
asked for permission to fortify their trading post, or factory, were given permission in general terms to
defend themselves. The rebels were easily crushed by the Mughal government, but the settlers'
defensive structure of brick and mud remained and in 1700 came to be known as Fort William. In
1698 the English obtained letters patent that granted them the privilege of purchasing the zamindari
right (the right of revenue collection; in effect, the ownership) of the three villages.
Although Job Charnock initiated the installation of the Kuthighat on the river, it was his son who
brought the Zemindary rights of the fledgling city, six years after the death of his father. In 1757, the
area was 5076 Bighas and 18 3/4 Katthas. The area was bounded by the Chitpur Creek on the north,
present day Lalbazar and the Chittaranjan Avenuae on the east, the Maidan and the Fort William on
the south and the Hooghly river on the west. In 1794, Lord Cornwallis first defined the boundaries of
the city. However it was in 1840, when for the first time the city limits were legally determined. These
were the Marhatta ditch on the north, Circular road on the east, and the Lower Circular road,
Kidderpur bridge, the Tolly's Nala up to the Hooghly river, which of course formed the boundary. In
1840, the city limits were extended to include Entally, Bebiapukur, Ballyganj, Bhowanipur and
northern part of Tollyganj. In this way the city went on to expand through inclusion of fresh suburban
areas by stages in 1931, 1951 and 1984. Present area of the city is 187.33 sq. km. (72.33 sq miles).
It may be noted that the Salt Lake area has now been brought under a separate municipality, called
the Bidhan Nagar Municipality. The increase in population with time can be gauged from the Table 7:
Table 3-1. Year wise Area and Population of Kolkata
Year Area of the city Population Source and authorities
1698 5076 bighas and 18 3/4 cottah
(1861 acres)
Wilson, Early, Annals I. p 286
1746 5472 bighas and 1/2 cottah Holwell, Tracts, 3rd. Edition, p 209
1762 6057 bighas and 13 cottahs Long, selections, no. 581
1794 4997 acres/ 20.31 sq. km. A.K. Ray, A Short History of Calcutta
l821 -do- 1,79,917 Assesor's estimate
1831 -do- 1,87,081 Captain Steele's estimate
1837 -do- 2,29,714 Captain Birch's estimate

3.5
1840 -do- 3,61,369 Simms's estimate
1850 -do- 4,13,182 Chief Magistrate's estimate
1866 -do- 3,77921 Dowleans's census
1872 -do- 447601 Chick's census (often considered unreliable)
1876 5037 acres/20.48 sq. km. 4,29,535 Beverley's census
1881 -do- 4,33,219 Census of 1881
1891 13,133 acres/53. 39 sq. km. 4,68,552 Census of 1891
1901 20,547 acres/83.52 sq. km. 8,47,796 Census of 1901
1911 -do- 8,96,067 Census of 1911
1951 28.34 sq. mile/73.40 sq. km. 25,48,677 Census of 1951
1961 95.62 sq. km. 29,27,289 Census of 1961
1971 98.79 sq. km. 31,48,746 Census of 1971
1981 98.79 sq. km. 33,05,006 Census of 1981
1991 187.33 sq. km. 43,99,819 Census of 1991
2001 187.33 sq. km. 45,80,544 Census of 2001
* Reduction in area is reportedly due to exclusion of Garden Reach
It would be also interesting to have a look at the drainage pattern of the region from a map that
approximately demarcates the regions at the beginnings of the British Colonial dominion in the Indian
Subcontinent. Figure 10 shows a small portion of the map by William R. Shepherd, titled The
Historical Atlas, in which it may be noticed that there are two distinct drainage channels flowing south
and south east from Kolkata (Calcutta then) apart from the river Hooghly which flowed approximately
towards the south west from Kolkata. In fact this provides a clue for the origin of the large tidal creeks
like the Matla, Thakuran, Raimangal, etc., as mentioned in Chapter 2, but without any head water
discharges. Actually, most of these creeks had been the erstwhile off-taking distributaries of the
Ganga Delta, and had been quite actively conveying substantial discharges to carve out a wide
channel. However, due to various reasons of which one could be human settlements, most of these
channels lost their head water catchment flows. This trend has been continuing since, as has been
apparent from the siltation of the river Hooghly, in he past decade. In fact, it was the reason why the
Farakka Barrage was constructed to divert an assured quantity of water into river Hooghly and
keeping it navigable.
A further detail may also be observed from the river Hooghly channels around Sagar Island. It might
be seen that the eastern channel (now almost defunct) had been quite comparable in size, though
smaller, than the main channel of the river at that point of time.

3.6
Figure 3-1. Map of India during 1700 – 1790 showing clear drainage channels flowing towards south
and east of Kolkata (Calcutta). From The Historical Atlas by William R. Shepherd, 1923.
By courtesy of Ian Poyntz (website http://homepages.rootsweb.com/~poyntz/India/maps.html)

3.7
3.4 Drainage Scheme of William Clarke
The first major modifications in the drainage system came in the wake of the Sepoy Mutiny, 1857,
when the responsibility of governance changed hands from the East India Company to the Imperial
throne of England by the Proclamation of Queen Victoria. Meanwhile, the Calcutta Municipality had
been established earlier in 1841 and the scheme for the "Water Carriage System" of the city as
prepared by its first engineer, Mr. William Clarke, was sanctioned on April 20, 1859 and cost an
estimated Rs. 34 lakh. The plans under the proposal were executed between 1860 and 1875. known
in civic parlance as the "Town System" as separate from the "Suburban System" which came later,
was combined sewerage cum drainage system, designed to drain an average rainfall of 6 mm (1/4
inch) per hour with cent percent run-off in addition to 182 litres (40 gallons) of domestic sewage per
capita per day. The underground drainage system comprised various sized conducts from 6.1 m (20
ft.) dia. brick outfall sewers to 15 cm (6 inches) dia. pipe drains. The main sewers, draining 4600
acres (around 18.50 sq. km.) of land and running generally from west to east, were connected on the
summit points to the penstocks opening into the Hooghly river to flush the sewers by the river water.
The bottom points at the east extreme were connected to the intercepting sewer laid along the
Circular Road. The underground drains measured around 2.44m high and 1.83m wide, with an eggshaped
cross section. Sewage was lifted at the Palmer's Bridge pumping station to a high level
sewer leading to Tangra and finally flowing into the Raja khal, an offshoot of the Bidhyadhari river,
which was a thriving tidal channel at the time. Three storm-water overflows were provided running
into the Circular canal. But the canal authorities resented this undesirable inflow into the canal and
finally further intercepting sewers were laid under the Canal West Road to intercept all these
overflows and to lead them on to the Palmer's Bridge pumping station. Later, in 1896, the scheme
was modified to include an additional drainage area, thus resulting in a total area of 19.2 sq. km.
Most of the drainage network as established under the Clarke’s scheme is still giving service to the
city, though the outfall into the river Bidhyadhari had to be changed later due to its high siltation. This
aspect is discussed in section 2.4.7.
3.5. Drainage scheme of Hughes and Kimber
Hemmed in by the Hooghly river on the west and the Salt lakes on the east, the city grew largely in
the south in preference to the north, where adequate land was difficult to come by. To meet the
drainage requirement of these freshly built up areas in the south, the Ballyganj pumping station was
proposed. The Palmer's Bridge pumping station also needed augmentation in capacity to dispose a

3.8
larger volume of sewage and drainage from the north. The next important scheme "The Bidyadhari
Outfall Scheme" was drawn up by Hughes and Kimber in 1894, received administrative approval in
1897 (January 11) and executive sanction in 1900 (June 18). The scheme which became operational
in 1903 incorporated the establishment of Ballyganj pumping station and augmentation of the existing
Palmer's Bridge pumping station and included the following:
• High level sewers from the pumping stations to point "A" at Topsia further cast.
• Excavation of Town and Suburban storm water reservoirs leading to Central lake channel at
Bantola, protected by three sets of Stoney's gates - two for the Town system and one for the
Suburban system.
3.6. Development of the Calcutta Sewage and Storm Water Disposal Committee and the
Calcutta Improvement Trust
Even when Kolkata lost its preeminence as the capital of the British Raj in India in 1912, its
expansion continued, as it still remained the most important center of economic and cultural activities
in the country. Barring the period during which the World War I was raging (1914-18), a systematic
approach for the improvement of drainage in greater Kolkata including Manicktola, Cossipur,
Chitpore and adjoining areas was initiated by the newly formed "Calcutta Sewage and Storm Water
Disposal Committee" (1922) and the Conference of Enginners convened by the Calcutta
Improvement Trust (1911) in 1924. The emerging recommendations inter-alia included formation of a
Main Drainage Board responsible for dealing with the problem of the disposal of the sewage and
surface water in Kolkata and its suburbs, greatest possible use of the existing storm water overflows
to the Hooghly river, Tolly's Nullah and other adjoining waterways and establishment of new storm
water overflows as necessary.
3.7. Rivers and channels in and around Kolkata
Kolkata is located in the lower part of the Bengal Delta and is naturally traversed by a number of
interlaced distributaries emanating from the apex of the delta. Due to Kolkata's nearness to the sea
face, most of these rivers and channels are tidal in nature. As the velocity of tide entering the mouth
of a tidal river is high and as there is a vast reservoir of unconsolidated sediment in suspension along
the sea face, the tide as it flows up these rivers is highly charged with sediment. Duration of ebb tide
in a tidal river is much longer than the duration of the flow tide. As the same volume of water must

3.9
ebb out as that flowed in, it follows that the average velocity of ebb is less than that of flow. Now the
sediment carrying capacity of flow is a direct function of velocity. Hence it follows that the ebb tide is
generally unable to carry back fully the sediment which has been carried up the tidal river during flow
tide. Consequently sediment will get deposited on the channel bed. Even a slight deposition of
sediment will go on accumulating, since the tides occur twice a day, throughout the year without a
break. As a result, the channel bed will begin to rise and its carrying capacity will deteriorate. The
deterioration will impede the propagation of tidal wave which would cause further deterioration and
the vicious circle would continue till the channel is completely dead.
To maintain the life of a tidal channel it is necessary to provide additional supply of water not
saturated with sediment, which has reserve capacity to pick up more sediment, to supplement the
tidal flow during the ebb so as to scour out fully that has entered the channel during the flow tide.
This can be done by (1) supply of upland water, (2) local drainage or (3) throwing open additional
spill areas. After the shifting of the main flow of the Ganga from the Bhagirathi to the Padma, upland
supply of sediment free flow got severely reduced to the Bhagirathi and the other distributaries of the
vicinity. The reduction was so severe that before Farakka Barrage diverted some flow into it, the
Bhagirathy remained completely cut off from the Ganga for full nine months in a year. The second
option is there; but local drainage is small in volume and seasonal in nature and so of very little
consequence. And it is very difficult to implement the third option. Anthropogenic interventions like
erection of marginal embankments for premature land reclamation and erection of fisheries and brick
fields have actually drastically reduced natural spill areas. Hence, it is extremely important to monitor
the condition of these tidal channels in and around Kolkata and to ensure their sustenance.
3.8. Deteriorating state of health of river Bidyadhari
The recommendations (1924) of the Calcutta Improvement Trust were made with the supposition that
the Bidyadhari river was capable of carrying off the entire volume of sewage and drainage effluent
from the city. But unfortunatery; the river by this time had already shown signs of distrees. When the
Central Lake Channel of the Bidyadhari river was selected as the city's outfall, the river was in fine
shape. It was 1500ft. wide and 60ft. deep at low water. Bidhyadhari used to get a considerable
supply of upland water including a portion of the dry weather flow of the Ganga (Bhagirathy channel),
which carried the major part of the flow of theGanga till the end of the 15th Century or early in the
16th Century. It also received the upland flow of the local channels like the Sunti, Nowi and Nona
Gang. Even when the main flow of the Ganga was diverted, it seems probable that it still continued to

3.10
receive, at least during the rains, a share of the Damodar flood, which had one of its outfalls into the
Hooghly near Kalna till 1660 and near Noaserai till about the middle of the 18th Century, both the
places being above the offtake of the Jamuna at Tribeni.
Erection of embankments by the owners of local fisheries, construction of locks etc., premature and
reclamation by raising marginal embankments within the spill area spelt disaster for the river.
Excavation of the Circular canal in 1830, New Cut canal in 1859, construction of Dhapa lock in 1883
and Bhangar Khal lock at Bamangola in 1898 accelerated the deterioration of the river. Finally
excavation of the Kristopur canal in 1910 sealed its fate by cutting off a large part of its basin area,
thereby reducing the upland discharge as well as the spill area. The rate of deterioration can be
gauged from the following statement of cross-sectional area of the river channel.
Table 3-2. Cross-Sectional Area of Bidhyadhari River Channel
Year 1883 1904 1917 1926 1936
Cross-sectional area (sq. ft.) 1 3674* 9702* 4700* 2440** 363**
Equivalent area sq. m. 1270.4 901.2
* Below 8.7 RL
** Below 9.75 RL
Hunter's Statistical Account of Bengal (1875) describes the Bidhyadhari river as follows: “The
Bidyadhari is a large river with a very circuitous course in the district, it flows from the Sunderbans in
the east, northwards past Harua (present day Haroa), where it takes the nake of the Harua Gang,
after which it takes a bend to the west and joined by the Nona Khal; it then flows south-west to the
junction of the Baliaghata and Tolly's Canals, and afterwards takes a south-easterly direction to the
town of Canning. Here it is joined by the Karatoya and the Atharabanka, the united streams flow
southwards through the Sunderbans as the Matla River, debouching upon the Bay of Bengal under
that name.”
L.S.S.O' Malley's Bengal District Gazetters, 24 Parganas, 1914 further states: “The portion of the
Bidhyadhari near Calcutta which at present serves as an outfall channel for the storm water and
sewage of the city, has for some years past been silting up at a rapidly increasing rate. The
acceleration of the silting process is attributed mainly to works in connection with local fisheries and
to the reclamation of portions of the Salt Water Lakes for rice cultivation, the effect being to decrease
the spill of water from the river over the adjoining land and consequently, to increase the deposit of
silt in the river bed. Other contributory causes have been the construction of the Dhapa lock, the
closing of tributaries in each of which the tide used to flow and ebb freely, and the canalization of the

3.11
Bhangar Khal. Observations taken between 1901 and 1912 show that, a mile below Bamanghata, the
bed of the river has risen nearly 25 ft. in 8 years, while in the section immediately below Bamanghata
lock the cross-sectional area has been reduced from 7700 sq. ft. to 3870 sq. ft.”
Analysing the situation O.C.Lees. C.S.I., Special Officer, Hooghly-Bidyadhari Canal Enquiry
Committee, surmised that the Bidyadhari has a very short remaining lease of life, and that in six
year's time it will be useless as an outfall channel for the sewage of Calcutta unless remedial
measures are taken. Bidyadhari River Channel was officially abandoned by a notification of the Govt.
of Bengal in 1928.
It may be of interest to note the drainage of Kolkata and its environs from a map (Figure 3-2) taken
from Imperial Gazetteer of India. New edition, published under the authority of His Majesty's
Secretary of State for India in Council. Oxford: Clarendon Press, 1907-1909. It may be observed from
the map that the river Bidyadhari had still been rather healthy at that time, draining into the Matla, on
which flourished the smaller port of Canning.
Figure 3-2. Map of Kolkata and its environs during by around 1907-1909 showing the
Beliaghata canal and the Katta Khal (Excavated Channel) draining the city of Kolkata.
By courtesy of Ian Poyntz (website http://homepages.rootsweb.com/~poyntz/India/maps.html)

3.12
3.9. Drainage scheme of Dr. B.N. Dey
As a result of loss of the Bidyadhari, the only available outfall channel, drainage prospect of Kolkata
became a matter of grave concern. A fresh suitable outfall channel had to be identified in the vicinity
in place of the decrepit Bidyadhari river. The city had grown in the meantime and so the internal
system of collection and conveyance of the drainage became woefully inadequate. Against this
disconcerting backdrop, Dr. Birendra Nath Dey (1891-1963), who later became the Chief Engineer,
Calcutta Corporation (1929-43) drew up a scheme incorporating augmented facilities for internal
drainage, as well as a new outfall channel around 30 Km. farther east in Kultigang, a tidal creek,
which ultimately flows into the Bay of Bengal via the Raimangal estuary.
Kultigang which now constitutes the main outfall of Kolkata's drainage opened up much later than the
Bidyadhari. In fact the former feeders of the Bidyadhari like the Nowi, Sunti and Nonagang, from
North 24-Parganas, changed their allegiance to the Kultigang. The Circular-Beliaghata-Newcut-
Kestopur and Bhangar Kata system emanating and catering to rapidly growing urban
conglomerations join the Kultigang. The SWF and DWF channels of Kolkata Corporation including
the discharge of the Tollygunj-Panchannagram outfalls into the Kultigang at Ghusighata. As
urbanization continues in eastern Kolkata further volume of flow will outfall into Kultigang.
The salient features of the Kulti outfall scheme are as under:
From Topsia lock water is directed by gravity up to Ghushighata through a 34 km long lined channel,
where it discharges into Kultigang through a sluice. This is the dry weather flow (DWF) channel.
From the Palmer Bridge (also often referred to as Palmer bazaar) pumping station there is a 7.47 km
long Town Head Cut (THC) drainage channel leading to the Storm Weather Flow, or SWF, channel.
This channel meets the DWF channel at Bantala where there is a primary sedimentation tank to
partially purify the effluents.
From the Ballygunje pumping station there is a 7.163 km long storm water floe drainage channel,
known as the Suburban Head Cut (SHC) which meets the THC at Bantala and flows as a combined
Storm Water Flow Channel, or SWFC.
The 1.829 km long storm water channel emanating from the Dhapa Lock pumping station meets the
THC at Makalpota. The bottom width of the SWF channel is 36.58m and has a carrying capacity of
76.47 cumec. The DWF channel is concrete lined and has a carrying capacity of 18.97 cumec. The
SHC is 34km long and at Ghushighata, it outfalls into the river Kultigang through two regulators
having 20 and 16 sluice gates, respectively.

3.13
It may again be of interest to note the formation of the new drainage channels at the time of the
establishment of the proposals of Dr. B. N. Dey. Attention is drawn to a map of Murray’s handbook
(1924) provided by Jill Grey and taken from the website of Ian Poyntz under the maps of Bengal
Presidency at http://homepages.rootsweb.com/~poyntz/India/maps.html, presented in Figure 3-3. It
may be observed from the map that the Krishnapur Canal (often referred to now as the Keshtopur
Khal) and the New Cut Canal had been in existence then. The proposed Grand Trunk canal is now
what is the Bagjola Canal. The salt lakes to the east of Kolkata (now partly Bidhan Nagar) is seen to
be connected to the tidal creeks, as inferred from the note stating the salt water lakes to be tidal.
Figure 3-3. Map of Kolkata and surroundings by 1924
By courtesy of Ian Poyntz (website http://homepages.rootsweb.com/~poyntz/India/maps.html)

3.14
3.10. CMPO and KMDA (originally CMDA)
The first Master Plan for Water Supply and Drainage within Calcutta Metropolitan District for the
period 1966-2001, was prepared by the Calcutta Metropolitan Planning Organization (CMPO) in
August, 1966 with the assistance of an Engineering Consortium, comprising Metcalf & Eddy Ltd. and
Engineering-Science Inc. of USA. The Master Plan included technical and other information of the
systems, analysis of the present status and recommendations for future programmes. These are in
short as follows:
• Destription of the existing infranstructure relating to water supply, sewerage and drainage of
the CMP district.
• Analysis of the main problems encountered in providing satisfactory service with regard to
water supply, sewerage and drainage.
• Exploration of alternative sources of water from surface as well as ground water.
• Present steps to improve the services in the short term should be integrated with long term
proposals to cater to the entire CMD area.
• Detailed programming of the proposals including phasing of the main elements and
recommendations for competent management circumscribing financial and legal aspects.
In the beginning proposals of the CMPO had been implemented by different agencies and
departments of the state govt. Later on Calcutta Metropolitan Development Authority, CMDA was
established for implementation.
3.11. Present Status of the city’s drainage system
The Kolkata Metropolitan area has been divided into 25 drainage basins, wherefrom the drainage is
carried off through, a number of natural or man-made channels into the natural trunk drains which are
basically tidal rivers and creeks. The present paper limits its scope to the basins and channels which
have some bearing on the drainage of the Kolkata Corporation area and its immediate environs.
Even now the major and more important parts of the city are drained by two old systems the Town
system and the Suburban system.

3.15
3.11.1. The Town System
The Town System which is the oldest of the two systems, comprises a set of feeder and trunk sewers
(running west to east in general), straddling the underground of the old city that draw the sewage and
drainage of the area, measuring about 19.3 sq. km. The trunk sewer running along the APC Ray road
from north to south also functions as an intercepting sewer for the trunk sewer like the Baghbazar
Street sewer, the Sovabazar Street-Grey Street sewer, the Nimtolla Ghat Street-Beadon Street
sewer and the Kolutolla Street-Mirzapore Street sewer. The AJC Bose Road trunk sewer starts at
Kidderpore Road close to the Hooghly river runs eastward up to Beckbagan and then turns
northward to Moulali. The Lenin Sarani sewer starts near the Hooghly river runs eastward to Moulali.
The three trunk sewers viz. the APC Ray Road, the AJC Bose Road and the Lenin Sarani meet at
Moulali junction and the combined flow passes further eastward through a special sewer section of
20ft. x 15ft.3in., known as the Town Outfall to the Palmer's Bridge Pumping Station (PBPS), which
has an installed capacity of pumping 1720 cusecs. One sewer from Convent Road leads to the PBPS
directly.
A number of subsidiary pumping stations have been constructed within the drainage area to relieve
drainage congestion in chronically waterlogged areas. These are: (1) Belgachia (2) Manicktala (3)
Thanthania.
It may be pointed out however that part of the Maidan area is now drained directly into Tolly's Nullah,
similarly the Thanthania PS delivery sewer discharges directly into the Circular Canal.
3.11.2. The Suburban System
The Suburban System developed as a result of later extension of the city towards south. Total
drainage area is 25.69 sq. km. In all there are six trunk sewers that convey the sewage and drainage
of the area, with the help of the feeder branch and lateral sewers, to the Ballyganj Drainage Pumping
Station (BDPS) with an installed capacity of 1275 cusecs. Three trunk sewers run from west to east.
These run below (1) Rashbehari Avenue (2) Hazra Road, and (3) Puddapukur Road. Two trunk
sewers run from north to south. These are (4) CIT Road (5) Tiljala Road. The sixth one is the one
running under Park Street and drains part of the Town System area.
In this system also there are a number of subsidiary pumping stations that relieve the individual
chronically waterlogged areas. These are : (1) Chelta Lock PS (2) Mominpore PS (3) Jodhpur Park
PS (4) Nimak Mahal PS (5) Kalighat PS. Due to some problems in the system the Storm Weather

3.16
Flows are diverted to the local surface drains like the Tolly's Nullah, Chetla Boat Canal, the
Panchannagram Canal and the Hooghly river.
3.11.3 Later Additions
The Dhapa Lock Pumping Station (DLPS) receives the sewage and drainage from the later
developments of North Eastern part of the city. There are four trunk sewers in the system. These are
(1) CIT Road, from Kankurgachi to Ultadanga (2) Ultadanga Main Road (3) CIT Road and Hem
Naskar Road (4) Beliaghata Main Road. The combined discharge of the first two trunk sewers is
conveyed to the DLPS via Ultadanga Drainage PS (UDPS). The remaining two meet at the CIT Road
junction and the combined flow runs under Beliaghat Main Road into the high level delivery sewer of
the UDPS to be finally led into the DLPS. There are a few Box Drains in the area that discharge into
the Kestopore Canal and the Beliaghata Canal. Tangra-Topsia System in the Central Eastern fringe
of the city caters to a low lying area which suffers from frequent waterlogging. Drainage of the area
mesuring about 5.17 sq. km. is effected through four pumping stations viz. (1) Topsia PS, (2)
Chingrighata PS, (3) Pagladanga PS, and (4) Kulia Tangra PS.
Very recently the Jadavpore and South Suburban Municipalities have been brought within the
jurisdiction of the Kolkata Municipal Corporation. For these latter areas the Tollyganj
Panchannagram, Monikhali, Churial, Keorapukur and Tolly's mullah etc. have to be properly
resectioned.
3.11.4. Formal distribution of administrative wards into drainage basins
The city of Kolkata may be divided into the following six major drainage areas:
1. Northern, or the Cossipore region
2. Central, or the town region
3. South-Central, or the suburban region
4. Southern, or the Tollygunge and Jadavpur regions
5. Eastern, or the Maniktola region
6. South-suburban area, or the Behala and Garden-Reach regions

3.17
Different area based drainage scenario is presented in Table 3-4.
Table 3-4. Kolkata drainage regions and corresponding Municipality Wards
Sl. No. Region
Area, in
km.
Wards
Drainage system
1 City proper 104 1-100 SWF, Beliaghata canal, Bagjola canal
2 Jadavpur 40 101-114 Tollygunje – Panchannagram canal. This
canal discharges to the SWF at Chowbhaga
pumping station outfall
3 South
suburban region
30.38 115-132 Chadial and Monikhali canals, which outfall to
Hooghly
4 Garden Reach 12.95 133-141
Total 187.33 141
In the above mentioned list, Cossipore area’s drainage is partially through the Bagjola canal and the
remaining through the river Hooghly. The Bagjola canal starts from the Dunlop Bridge on the B T
Road and outfalls at Ghushighata on the river Kultigang through a sluice. The total length of the canal
is around 38 kms. The important contributing branches of this canal are the Udaipur canal, Sonai
canal, Cantonment canal. The highly congested areas of Noapara Akshay Mukherjee Road,
Bediapara, Jessore Road, Dumdum Road, VIP Road, drain into this canal. The total cumulative
drainage area for the Bagjola canal is around 164 sq. km. The stretch of the canal from its origin up
to the VIP road is called the Upper Bagjola canal, whose length is 9.23 km and drains around 49.20
sq. km. From the VIP road up to the outlet, the name of the canal is Lower Bagjola canal, whose
length is 28.818 km and drains around 114.80 sq km. The upper reach of the canal drains the serving
regions directly, but the central and the lower portions of its drainage area outfall their storm water
into the canal through the Dutta Bagan pumping station. The catchment area to the west of the B T
Road drains to the river Hooghly. The Lower Bagjola canal is connected to the Bhangar kata khal at
three places. The first of this is through through link near the Mision Bazar at Kestopur through a linkregulator.
The second connection is through the Jowal Bhanga canal at Rajarhat and the third is in

3.18
the Bhangar region through the Chowreswar canal. The different branches of the Lower Bagjola
canal are named as BB1, CC1, DD1, EE1,, EE2, and XX1.
The central drainage catchment of the city lies between Galiff Street on the north, the park Street to
the south and the region between the Hooghly on the west and the Circular canal / the Sealdah-
Ballygunje railway line on the east.
The South-Central or the suburban region extends from A J C Bose Road, Park Street and the
Topsia Road on the north, up to Ballygunje – Budgebudge Railway line on the south. A portion of the
discharge of the Ballygunje pumping station on the DWF and the SWF channels during monsoon
rains is also sometimes directed towards the river Hooghly.
The storm water of the Southern or the Tollygunge and Jadavpur drainage regions, is partially
through the Tolly nullah and partially through the Tollygunge – Panchannagram canal that outfalls
into the Suburban Head Cut.
The drainage of the Eastern, or the Maniktola region, is partially through the Dhapa Lock Pumping
station and partially through the Krishnapur canal.
The South-suburban area, or the Behala and Garden-Reach regions, drain into the river Hooghly
through the Chadial and Monikhali canals, which have sluices at their outlets.
3.12. Rainfall scenario in the city of Kolkata
The rainfall characteristics of the city of Kolkata vary from an average of 1610 mm at Alipore to 1510
mm at Dumdum. At times, the daily rainfall exceeds 300 mm. Some of the excessive rainfalls
recorded for the city are provided in the following table.
Table 3-5. Amount and duration of some exceptional rainfall over the city of Kolkata
Date Rainfall in mm Duration
30 September 1738 381 5 hours
14 August 1788 253 20 hours
20 June 1893 213 36 hours
19 September 1990 369 24 hours

3.19
20 September 1990 275 24 hours
13 May 1913 25 10 minutes
26 September 1978 to
1 October 1978
735.30
5 days
(Maximum on 28 Septem360.6
1978)
3 June 1984 to
499.25
4 June 1984
23 September 1999 to
334.10
25 September 1999
It may be observed that though the drainage system of the city of Kolkata, as designed by William
Clarke, was based on a probable rainfall of a quarter inch (6 mm) of rainfall an hour, which is
equivalent to about 6 inches (150 mm) of rainfall in a day, there have been occasions when the
rainfall has exceeded this amount leading to serious congestion of the storm disposal system leading
to water logging in the city. There are further reasons also to contribute to increasing instances of
water logging condition in the city, and these have been discussed in the following paragraph.
3.13. Nature and problems of Kolkata's Drainage System
The city of Kolkata and its surrounding urban spaces are confronted with serious problems of
waterlogging as a result of cyclonic activities due to the following reasons.
At the time of high cyclonic activity over the region causes a huge accumulation of runoff water,
which has been increasing over the years due to paving of natural ground as a result of rapid
urbanisation. This water is drained, as mentioned before, through nearly 30km long channels to the
east of the city and discharged into the river Kultigang, which is connected to the Bay of Bengal
through the tidal creek of Raimangal. As such, at the outfall point of the water channels, the normal
tidal variation is such that a flow by gravity into Kultigang is only possible for only about 7 to 8 hours a
day. Naturally, at the time of a cyclone, the general water level of the tidal creeks rise due a rise of

3.20
the ocean level as a result of storm surges. This causes flow accumulation in the drainage channels,
which in turn, causes backflow into the city.
The waterlogging problem may be ascribed to the typical geographical feature of the city being of
saucer type, the central portion being of lower elevatron and pumping is required to remove the
waterlogging as there is hardly any scope for gravitational drainage. The eastward drainage does not
pose much serious problems while the areas, viz. Amherst Street, Thanthania, Chitpur, Free School
Street, Camac Street, Sarat Basu Road where sewers have a north-south alignment have chronic
waterlogging problem. The inadequate road surface area of the city of only 6-8 percent aggravates
the waterlogging problem. The storm water from the buildings instead of draining into the sewers
through the yard gullies is discharged onto the inadequate road surface. Moreover, the gully pits on
the roads, through which the water should drain out are inadequate in number and often choked
owing to lack of maintenance. Further, rain washes solid waste to the mouths of gully pits, blocking
the free flow of water into them. Besides, the city sewer system has no separate dry weather and
storm weather flow arrangement thus resulting in major and minor underground trunk sewer lines
being badly silted up for absence of cleaning at regular intervals and this has made the reduction in
flowing capacity of storm weather flow considerably to the extent of about 30 percent.
3.14. Drainage of Bidhan Nagar (Salt Lake)
Salt lake is divided into three zones namely Sector I, Sector II, and Sector III which have different
topographical and consequential drainage features. While storm water of Sector I, and Sector II flow
into Kestopur Canal by gravitation, nearly 40 percent of the drainage of Sector III is effected by the
pumping station at DE-block and rest through gravitation flow into Eastern Drainage Canal. It can
easily be understood the vital part these two canals namely Kestopur and Eastern Drainage Canal
play in overall storm water management of Salt Lake. Since both these two canals originate from
Kolkata desilting of these two canals will contribute a lot for swift drainage of Salt Lake, in addition to
the benefit of Kolkata Municipal area.
It must be remembered that Bidhan Nagar was formed by filling up of low-lying marshy lands with
sand from the river Hooghly. Not all places of the reclaimed land was filled up the same extent.
Hence, certain portions of the township which are not that high suffer fromdrng congestion. Also, the
drainage channels of Kestopur Canal and the Eastern Drainage Canal have silted up considerably
from their original design sections, resulting in backflow of the township’s internal storm water
drainage.

3.21
3.15. Kolkata city’s drainage system – a closer look
The physiographical setting of Kolkata is such that the land slopes from the higher banks of the river
Hooghly towards the marshlands of the east that connects to the network of rivers and channels
draining to the Bay of Bengal. In fact, there are pockets in the city that are rather low-lying and water
has to be evacuated from the storm drainage system (underground in most parts of the city proper)
by pumping. It has been observed that there is a general trend of water logging in the regions which
have a north – south alignment of the underground drainage pipes, some of the areas being as
under:
1. Amherst street
2. Thanthania
3. Chitpur
4. Free School street
5. Camac street
6. Sarat Bose Road
The problem is aggravated by the fact that streets and roads occupy just about 6 to 8 percent of the
city area. And for many of the large houses, the roof top or courtyard rainfall water is led to the road
side gutter instead of being directly led to the underground drainage system. The road side gutters
are not always sufficient in size and are often covered with garbage, thus causing blockage of the
water from entering the pipes below.
It must also be reiterated here that the drainage system that still supports the flushing of the storm
water in the Kolkata city proper is based on the original design of William Clarke, with some additions
in the later years, Hence, there has really been not much of augmentation of the original system and,
on the other hand, there has been a steady deterioration of the system by way of sediment
deposition. It is understood that the cross sectional areas of these pipes have been reduced to 30
percent of their capacities, in many stretches. Some details of the pumping system and the open
drainage channels, or khals as they are called in local parlance, is given in the following sections:
3.15.1. Pumping arrangements for the drainage system
The saucer shaped topography of the city of Kolkata has led to the establishment of a number of
pumping stations to flush out the storm water. These are maintained by different agencies, and a list
of some of the important pumping stations is given in Tables 3-6, 3-7 and 3-8.

3.22
Table 3-6. Major pumping stations for the city of Kolkata
Sl. No. Location Capacity Working under
1 Palmer bridge (bazaar)
Est.- 1876
2 Ballygunje
Est.- 1890
3 Dhapa lock
Est. 1958
Storm water pumps: 4 units
@ 250 each = 1000 cusec
Waste water pumps: 8 units
with total capacity of 750
cusec
Storm water pumps: total
capacity of 850 cusec
Waste water pumps: total
capacity of 825 cusec
Storm water pumps: total
capacity of 800 cusec
Waste water pumps: total
capacity of 80 cusec
Kolkata Municipal
Corporation
Kolkata Municipal
Corporation
Kolkata Municipal
Corporation
4 Topsia Total capacity of 205 cusec Kolkata Municipal
Corporation
5 Chowbhaga (original) Total capacity of 450 cusec Irrigation and
Waterways
Directorate
6 Chowbhaga (additional - I) Total capacity of 500 cusec Irrigation and
Waterways
Directorate
7 Chowbhaga (additional -
II)
Total capacity of 500 cusec
Irrigation and
Waterways
Directorate
8 Keora Pukur Total capacity of 200 cusec Irrigation and
Waterways
Directorate
Table 3-7. Minor pumping stations for the city of Kolkata
Sl. No. Location Total Capacity Working under
1 Birpara 50 cusec Kolkata municipal authority
2 Maniktala 24 cusec Kolkata municipal authority
3 Ultadanga (Old) 20 cusec Kolkata municipal authority
4 Pagladanga 40 cusec Kolkata municipal authority
5 Kalighat 35 cusec Kolkata municipal authority
6 Kulia tangra 30 cusec Kolkata municipal authority
7 Lake town 21 cusec Public Health Engineering
Department
8 Cossipore – Dumdum 156 cusec Public Health Engineering
Department
9 Chingrighata 100 cusec KMWSA
10 Hrishikesh Park 30 cusec KMWSA

3.23
Table 3-8. Lifting / boosting pumping stations
Sl. No. Location Total Capacity Working under
1 Belgachia (R G Kar Hospital) 28 cusec Kolkata municipal authority
2 Ultadanga (New) 440 cusec Kolkata municipal authority
3 Maniktala (crossing of Raja
12 cusec Kolkata municipal authority
Dinendra Street and
Vivekananda Road)
4 Nimak mahal (Near circular 100 cusec Kolkata municipal authority
Garden Reach road)
5 Mominpur 6 cusec Kolkata municipal authority
6 Chetla lock 6 cusec Kolkata municipal authority
7 Jodhpur park 20 cusec Kolkata municipal authority
3.15.2. Open drainage system for conveying Kolkata’s storm and dry water flow to their
respective outfalls
The city itself has a network of underground drainage pipes, as mentioned above, but as the flow is
directed eastwards, these are discharged into open surface drains. Some of the drains are within the
city, but there are three major drains, rather canals, that drain the entire city discharge into the River
Kultigang, about 35 kms from the city. There are a couple of other drainage channels that flush out a
portion of the city’s water to River Hooghly. A brief description of each of these channels are given in
this section.
The Northern part of the city discharges about 300 cusecs (8.50 cumecs ) of water under normal
rainfall into Bagjola Khal through several pumping stations, for the southernmost areas like Behala,
Garden Reach, the drainage is effected in river Hooghly through Churial Khal, Manikhali Khal,
Tolly's Nullah etc. though the tidal effect in Hooghly river causes considerable period of blockage
during drainage time. Similarly, the city's main drainage outfall system, viz. SWF channel consisting
of SHC and THC, which outfall into river Kulti about 35 KM from Ballygunge Pumping Station is also
a tidal one, the drainage can be effected only for 51/2 hours in every 12 hour cycle on an average.
Moreover, the SWF system mainly catering city drainage in course of its long journey, also receives
drainage water from city contiguous part and also from rural and urban areas. The domain of
drainage under SWF system from the metropolis of Kolkata and the rural areas may be summarised
as in the following table.

3.24
Table 3-9. Drainage basin areas
1. City proper (including Boichitala) 80% of 104 sq km = 83sq.km. Calcutta contiguous
2. Jadavpur/Tollygunge Panchanangram Basin = 38 sq.km( 95% ) Subarban areas 121
3. South Salt Lake Basin = 36 sq.km.
4. Kheyadah Basin =8.50 sq.km.
Contiguous urban areas
177 sq.km.
5. Sumidgiri Basin =18 sq.km.
6. Karaidanga Basin = 10.75 sq.km.
7. Dudhbibi Basin = 42.75 sq.km.
8. Rajapur Basin II - 11 .00 sq.km.
9. Juljulgachi Basin = 40.00 sq.km.
10. Laugachi Basin = 10.25 sq.km.
Total 298 sq.km. Say 300
SWF channel system
According to the present scenario, the Storm Water Flow and Dry Weather Flow Channels serve
as drainage and sewerage arteries of about 144 Sq. Km. of the city of Kolkata including Tollygunge
Panchannagram Basin ( T.P. Basin ) and about 175 Sq. Km. of rural area along with its flow line
towards East up to River Kultigong. The Three separate Channel Systems are:
Town Head Cut (T.H.C.) Channel having a length of 7.47 Km. T.H.C. starts from the outfall of Palmer
Bazar Pumping Station and meets S.H.C. at Bantala Regulator.
Feeder Channel to T.H.C. having a length of 1.829 Km. This feeder starts from Dhapa Lock Pumping
Station and meets T.H.C. at Makalpota.
Suburban Head Cut ( S.H.C.) Channel having a length' of 7.163 Km. S.H.C. starts from Ballygunge
Pumping Station and receives T.H.C. at the downstream of Bantala Regulator.
The system also receives storm water from TP Basin through 3 nos. pump houses at Chowbhaga.
The two Channels i.e. T.H.C. and S.H.C. meet at Bantaia and form the S.W.F. Channel which
reaches River Kultigong at Ghushighata. The combined length of S.W.F. Channel system is about 44
Km. Other relevant data of the channel are as follows:
Length of SWF channel from Bantola to Kulti
27.20 km
Length of Town Head Cut (T.H.C.) channel
7.47 km
Length of channel from Dhapa Lock Pumping Station to the meeting point of T.H.C. 1.829km
Length of Suburban Head Cut (S.H.C.) channel
7.163 km
Total
43.662 km
There exists a huge difference between the present position and the old design considerations.
Virtually it has become inadequate leading to the necessity of providing additional measures for

3.25
alleviating drainage congestion. The reasons for drainage problems of this system may be
summarized as follows:
• Drainage lockage while High Tide and rising of low water level due to rise of river
bed governing the outfall efficiency in an adverse way.
• The old channel section has nearly remained unchanged n spite of big changes
in drainage load.
• Increase of population density resulting in additional loads.
• Huge change in land-use-pattern
• Drastic reduction in spill areas.
The drainage discharge mainly of the following Boroughs is being served by the SWF channel at
present. Part of Borough IV, Part of Borough V, Part of Borough VI, Part of Borough VII, Part of
Borough VIII, Part of Borough X, Part of Borough XI and Borough XII. During heavy rainfall,
substantial area under the above Boroughs gets waterlogged and duration of inundation lasts for a
long period due to inadequate capacity of the existing drainage system outfalling in SWF channel.
To overcome the severe drainage problem, KEIP has taken up sewage and drainage project mainly
for the added areas of Kolkata to address the drainage inadequacies of the area- specially falling
under Borough VII, XI, and XII by construction of new pumping stations and also by augmentation of
the existing pumping stations. This will result in additional discharge in SWF channel.The 3rd
additional pump house at Chowbhaga and the new pumping station at Borough VII will increase the
present drainage load of SWF channel at Chowbhaga point by 25.51 + 70% of 13.00 (since the
discharge of the ail the pumping stations will not synchronize at the same time) = 34.61 m3/sec. The
resulting afflux will surely affect the Full Drainage Level of the upstream channel, too. The Full
Drainage Level (FDL) of crucial Topsia point 'A' will thus be increased from the already strained
inconvenient level during tidal lockage. Due to increase in FDL, more areas will be waterlogged for
longer duration.
The design discharge of SWF channel before reaching additional pump house complex of
Chowbhaga is 46.44 m3/sec. and the proposed pumped discharge from Borough VII is about 9.1
m3/sec. The total discharge comes to about 46.44 + 9.1 = 55.54 m3/sec. The peak discharge
capacity of SWF channel required before reaching the proposed 3rd additional pump house outfall at
Chowbhaga is 55.54 + 8.45 + 11.34 + 11.34+ 25.51 m3/sec. = 112.18 m3/sec. (the capacity of the
Old Pump House, if. Additional P.S., 2nd. Additional P.H and proposed 3rd.Additional P.M. are 8.45
+ 11.34 + 11.34+ 25.51 m3/sec respectively). The objective of setting up the proposed dumping
stations is to provide relief to its catchment area from water-logging upto the design year 2035. This

3.26
will lead to significant improvement of environmental quality in the area and also the economic
improvement of the community.
The design discharge with the parameters given below works out to 86.65 m3/sec. in SWF channel in
the reach of down stream of Chowbhaga. (Figures 2a & 3)
Bed width - 26.20 m
FSD - 3.83 m
Hydraulic gradient - 0.00007
Side slope - 1.5 H: IV
Rugosity coefficient - 0.025
Design discharge - 86.65 m 3 /sec.
The additional discharge to be carried by SWF is 112.18 - 86.65 = 25.53 m 3 /sec., say 25.50 m 3 /sec.
Bed width - 50.00 m
FSD - 3.55 m
Side slope - 1.5 H : 1 V
Hydraulic slope - 0.00007
Discharge (calculated) - 141.00 m 3 /sec
It is found that the tide lockage period on river Haroagong - Kultigong has increased substantially and
average lockage period during peak monsoon when, the river rules high, will be 8.95 hours in 12.25
hours of tide cycle. It means that the tide lockage will be about 18 hours in 24 hours.
There are two existing sluices at the outfall of SWF and DWF channels through which the discharge
is drained into Haraogong - Kultigong river. These two channels meet before outfall in the river. The
discharge in DWF being small in comparison to that of, SWF, the discharge in DWF has been
ignored in computation. During tide lockage for about 18 hours in 24 hours, discharge to the river is
seriously hampered. This discharge can drain to the river for hardly 6 hours in 24 hours. With heavy
discharge in the channel and drainage being stopped during tide lockage, the full drainage level
upstream of the sluice starts rising causing water-logging in upper reaches.
The lower part of SWF Channel consists of mainly rural and semi-rural area. Owing to pressure of
population, rapid urbanization is going to change the nature of the area. Consequent upon the
changing of rural and semi-rural into the semi-urban and urban area the drainage load in the channel
will increase rapidly.
Total drainage discharge at outfall has been increased by 10% beyond the projected year 2035 i.e.
10% of 141 cumec to account for the urbanization = 14.10 m3/sec which will be going to add to the
already overloaded SWF Channel.

3.27
Some of the other drainage arteries of the City proper and the added areas viz. Beliaghata-Circular-
New Cut Canals, Kestopur-Bhangarkata Khal and Tolly's Nullah, which are discussed below.
Circular-Beliaghata Khal
Circular canal was originally one of the principal navigational arteries, the pioneer in this process was
Mr. Tiretta, the first planning and fixing up the alignment was prepared by him. The proposal was
however turned down by Lord Wellesley. Another proposal was submitted by Major Scholch in 1824
but he died in 1826 in Anglo-Burmese War. Excavation of the canal was started in 1829 and
according to his proposal was completed in 1833. Chitpore Lock was also set up during this year.
The Circular Canal, originally conceived as a navigational channel has no gradient Originating at
Chitpore, it bifurcates near Gaznavi Bridge ( near R. G. Kar Hospital ) and terminates at E.M. Bypass,
the length of this canal being 8.50 Kms. The eastern and branch is known as New Cut Canal
up to VIP Road Bridge. For some time past, the channel has been serving as a drainage channel.
The Circular Canal is connected with the Hooghly at Chitpore through an outfall sluice and a
navigational lock and with Eastern Drainage Channel near Eastern Metropolitan Bye-Pass.
New-Cut - Kestopur-Bhangar Kata Khal
Further increase in water traffic initiated excavation of New Cut Canal which was started in 1855-56
and completed in 1856-59. It was also thus excavated as a navigation channel with no gradient. The
canal system takes off from Circular Canal about 275 metres south of Belgachia (Gaznavi) Bridge.
River Bidyadhari at that time had a minor tributary viz. Central Lake Channel, 91/2 miles (15.30
Kms.) in length which used to outfall into the river at Bamanghata, originating in Dhapa Bill. The Lake
Channel was however heavily silted up in 1897 thereby leaving the only means of waterway
communication in total disarray between Bamanghata and Dhapa. To provide navigational
facilities in these areas, excavation of Kestopur Khal started in 1908-10. It used to take off from
Aaratoon Jute Mill and outfalling into Bhangar Kata Khal which was excavated during 1897-98. The
Kestopur -Bhangarkata Khal system outfalls into river Kultigong through an outfall system. The
lengths of this canal system is about 39 Kms. The canals are presently serving as a drainage
channel catering the drainage discharge of Lake Town, Bangur, Dum Dum Park, Salt Lake, Rajarhat,
Bhangar and some other rural areas Kestopur Khal forms the northern boundary of the Salt Lake
City. The Eastern Drainage channel as stated earlier outfalls into Kestopur Khal. This canal system
was provided with navigational facility and was known as a part of "Inner Sundarban Route" and
used as a waterway connecting erstwhile East Bengal, now Bangladesh. The navigation through the

3.28
locks, one at Chitpur and another at Kulti has stopped since 1987. There is serious thinking on the
revival of this navigational system.
The southern parts of the metropolis are the added area under K.M.C. The drainage arteries are
Tolly's Nullah. Tollygynge-Panchannagram ( TP ) Khal which cater drainage of Jadavpur area. The
TP Khals in turn discharge into SWF channel through Chowbhaga Pumping Station, while the
drainage in the fringe areas of the metropolis under South Suburban Municipality in Behala and
Garden Reach areas is catered through Monikhali and Churial Khals through outfall sluices outfalling
into river Hooghly. The particulars of these drainage arteries are narrated in the following paragraphs.
Tolly's Nullah
This channel is basically a navigational channel having no regulatory arrangement either at intake or
at outfall. Tolly's Nullah is named after Major William Tolly who worked as an Engineer under East
India Company. He submitted a proposal to use the bed of the almost dead channel of Adiganga and
as a private venture excavated the channel under a temporary grant of land and to levy canal tolls
and completed in 1776. It was opened to navigation in 1777. The total stretch of 17 miles ( 27.5
Kms.) of the channel was named after him and is better known as "Tolly's Nullah" and it used to
outfall into river Bidyadhari near Sarnukpota or Tarda Port. The Govt took it over in 1804. The section
was increased for the passage of larger ships, barges and boats. It had been highly prone to silting
especially near and above Tollygunge where the tides of Bidyadhari and Tolly's Nullah used to meet
and had to be constantly cleared to keep it navigable. It drains a substantial area of the southern part
of the city including Keorapukur Basin, Regent Park, Bansdroni and other areas adjoining to cause
bank in the course of its 15.50 Km stretch from Garia Railway Bridge to Hastings on river Hooghly.
Boat Canal is an important tributary of Tolly's Nullah and it carries the sewage and storm flow of
C.P.T. area and is the biggest source of pollution of Tolly's Nullah.
Tollygunge-Panchannagram (TP) Khal
The Tollygunge-Panchannagram (TP) Khal, stretching a total length of 6.75 Km. along with its
intercepting channels of 5 Kms. and branch channels of 18 Kms. plays a formidable role to drain a
portion of added area of KMC viz. Jadavpur, Santoshpur, Kasba, Tiljala,etc. It happened to be one of
the lowest pockets, being almost a swampy area. Between the years 1934 and 1940, the area was
virtually waterlogged and an acute situation of distress, particularly in the Kasba and Haltu areas,
provided for a long time. Partial relief from the acute drainage congestion was however given in 1941
by Tollygunge Municipality by allowing the storm water from this area to be discharged into the reexcavated
Storm Water Flow (SWF ) channel at Chowbhaga through a sluice. The drainage situation

3.29
was slightly improved but the ventage at the sluice was too inadequate. Subsequently a scheme was
originally framed to drain a total area of 33.15 sq.km. (12.80 sq.mls.) of which 22.53 sq.km. area is
urban and 10.62 sq.km. being rural. Drainage indices @ 75 mm per day for urban and 20 mm for
rural area were adopted. The area is located on the east of the Budge Budge Rly. line and Tolly's
Nullah, Salt Lake Basin on the west, on the south of SWF channel and on the north of Tolly's Nullah.
The scheme was executed in 1972. It is one of the largest drainage arteries of the Kolkata
Metropolitan area. Apart from domestic discharges, it carries industrial wastes, decaying materials
and carcasses. Lots of unauthorised shanty dwellers residing on its banks also use it for their
sanitary purposes and disposal of solid wastes. The area is very much prone to water logging having
some low lying pockets.
T.P. Basin Drainage Scheme was designed to drain the additional urban run-off by excavating
another new lower level drainage channel named as "Intercepting Channel" connecting the Branch
Channels BB1, CC1, DD1, EE1, segregating the urban area from rural area and the urban run-off
would find its way through these channels to the Intercepting channel and the old TP Main Canal with
its outfall pumping station would cater for the rural run-off and some of the urban run-offs through
the other branch channels, viz. A1-A2, A3-A4, A5-A6 It was imperative to provide for pumping for
disposal of the additional discharge from the basin and accordingly, the new pumping station,
known as Chowbhaga New Pumping Station was constructed near the old one with 10 nos. of pumps
of 50 cusecs each making a total of 500 cusecs ( 14.16 cumecs ).
Originally, there were 9 nos. of Pumps of capacity 50 cusecs each at Chowbhaga being constructed
during the year 1966-67. Afterwards, the basin condition changed, additional basin area was
included, thereby increasing the area to 47.40 sq. km. (18.30 sq.mls.). A scheme for installation of
additional pumps was drawn up to drain out the extra water due to urbanisation and inclusion of more
rural areas. The capacity of new additional pump house was so designed that this pump house along
with the existing ones may cater a limited discharge of 41 cumecs (1450 cusecs) to the SWF
channel. As such, 1 5 nos. of pumps in total of capacity 50 cusecs each were installed.
The drainage of the South-Suburban and the Garden Reach areas falling within Kolkata Municipal
Corporation Ward nos. 115 to 132 and 133 to 141 areas is catered through Monikhali, Churial
Keorapukur Khals, a brief outline of which is discussed in the following paragraphs.
Monikhali Khal
Monikhali Basin, with an area of 54.00 sq. km. consists of two main drainage arteries (1) New
Monikhali Khal and (2) Old Monikhali Khal, the lengths being 6.931 Km. and 4.998 Kms.

3.30
Respectively. The discharge of New Monikhali Khal is 44.16 cumecs (1559 cusecs) and that of Old
Monikhali Khal is 3.82 cumecs (134.88 cusecs), The Khals ultimately outfall into river Hooghly
through outfall sluices.
The Khals fall within Maheshtala Municipality and are carriers of drainage water of this area including
sewage compnsing domestic waste as well as discharge coming through Begore Khal carrying the
discharge of Municipal Corporation.
Both the chananels flow through densely populated area. As such the channels require to be lined
particularly the side slopes require to be renovated by protective works to avoid slips. New Monikhali
Khal requires immediate desiltation to accommodate the full supply of Begore Khal.
Churial Khal
Churial Khal system drains a total area of 164.98 sq.km. ( 63.70 sq.mls.) of which 141.65 sq.km.
(54.69 sq.mls.) is rural and 23.33 sq.km. (9.01 sq.mls.) is urban. The main Khal, with a length of
17.59 Kms. along Behala to Purba Barisha under Kolkata Municipal Corporation outfalls into river
Hooghly through a 5-vented outfall sluice of 28.32 cumecs (1000 cusecs) capacity at Churial
under Budge Budge Municipality. The diversion channel, with a length of 7.01 Kms. flowing from
Mouza Mithapukur to Pujali Notified Area drains into river Hooghly through a 10-vented sluice of
capacity 56.33 cumecs (1989 cusecs). Over and above, the system includes Churial Khal Extension
of length 1.996 Kms. from Behala Motilal Gupta Road to Purba Barisha at Joka, 15 nos. branch
canals of total length of 50.32 Km. and as many as 20 nos. of sub-branches. The system caters
drainage of areas falling under P.S. Budge Budge, Bishnupur, Maheshtala and Thakurpukur. Desilting
of the Khals is of urgent necessity to assure proper capacity of drainage channels and the
Khals require to be lined.
Keorapukur Khal
The Keorapukur Khal, with a length of about 32 Kms. and a total basin area of 38,83 sq.km, has two
directional outfalls, one into Diamond Harbour creek and the other into Tolly's Nullah near Kudghat.
Out of its total length, 7.5 Km stretch lies within Kolkata Metropolitan area which drains water of a
catchment area of about 30 sq. kms. at the northern end and outfalls-into Tolly's Nullah. This
channel serves the drainage requirement of Bakeswar, Keorapukur, Putiary areas which are totally
urbanised now. 10.9.2 The canal, being badly silted up and reduction of canal section is unable to
drain out the discharge of the catchment area. The encroachment on the banks of the canal poses
serious problem for execution of canal improvement works. The Keorapukur Drainagae Pumping

3.31
Station, with a capacity of 4 x 50 = 200 cusecs was constructed in 1966-67 to drain out the water into
Tolly's Nullah.
3.16. Outfall sluices
At the outfall at Kultigong, the cross section of the river is gradually decreasing, resulting in
inadequate disposal capacity of the city’s drainage. Further, at the time of cyclonic storms, the
ingress of the storm surge wave combined with tides casuse a lockage at the outfalls. In order to
dispose the high volume of runoff (which is increasing with the rapid urbanisation of the Kolkata
environs), higher capacity pumps are required. It is estimated that the tidal lockage period has
steadily increased over the years and presently is about 18 hours in 24 hours. The different situations
possible for the outfall and the aggravation of the tidal lockage are shown in the following figures.
Figure 3-4. The downstream of the outfall (the Kultigong River) at low tide – outflowing sluice
Figure 3-5. The downstream of the outfall (the Kultigong river) at high tide – sluice gates closed

3.32
Figure 3-6. The downstream of the outfall (the Kultigong river) at high tide – sluice gates closed but
water has accumulated in the drainage channel (tidal lockage)
The following images depict some of the situations. For example, Figure 3-7 shows the outfall
of the SWF (combined with DWF) channel at Ghushighata – showing the sluice vents at the
bottom (below the closed shutters). The SWF is able to discharge to the river as the level of the
Kultigong at this time is at a low level, unaffected by tide. Similar outfalls exist for the Kestopur
canal as well as for the Bagjola canals. Of course, a high capacity pumping station has been
installed at the Bagjola end to pump out the water at the time of tidal lockage.
Figure 3-7. Kultigong at low tide – drainage channel discharging: a view from upstream

3.33
Figure 3-8. Kultigong at low tide – drainage channel discharging: a view from downstream
Figure 3-8 shows a view of the same sluice vents taken from the Kultigong river side. The
water is exiting through the flap gates which are now open due to a low level of the river.
Figure 3-9 shows the tail end of the SWF/DWF downstream end below the outfall meeting the
river Kultigong.
Figure 3-9. A view of the tail end of the drainage channel meeting Kultigong
DRAINAGE CHANNEL TAIL END
KULTIGONG AT LOW TIDE

3.34
Figure 3-10 shows the tail end of the SWF/DWF channel that is at a high level due to a high
tide of the river Kultigong. The river is connected to the bay of Bengal through the river
Raimangal to which it connects about 50 kms downstream.
Figure 3-10. Kultigong at high tide – sluice gates closed (below water): a view from downstream
The River Research Institute, Govt. of West Bengal had in the past carried out sustained
studies on the status of the Kultigang. These studies carried out till 1979, as shown in the Table
3-3 below, did not show much variation. But in the recent past the channel has been subjected
to larger discharge with more pollution. In the future also this channel will have to deal with still
larger volumes of discharge and perhaps more pollution. So a stringent surveillance on the
state of this channel is urgently called for.
Table 3-3. Hydraulic Condition of river Kultigang: Annual average cross-sectional areas in sq.
meter below 1.14 M. (3.75 feet) PWD at different points on the river Kultigong.
Year Nowi/Sunthi Haroahat Ghusighata Malancha Bamnajore
junction
244 M D/S of
Kulti outfall
1952 33 305 685 2123 4323
1953 34 304 719 2076 5025
1954 31 302 690 1893 4835
1955 30 311 718 1793 4872
1956 29 343 743 1843 4968
1957 27 336 721 1787 5013
1958 24 330 749 1690 4886
1959 24 301 665 1474 4692
1960 23 321 671 1531 4758
1961 30 335 648 1893 4171

3.35
1962 22 321 725 2001 4919
1963 26 378 762 2246 4576
1964 26 352 783 2037 4281
1965 26 340 875 1897 4325
1966 19 371 929 2002 4621
Data unavailable for 1967-1972
1973 74 325 741 1463 4847
1974 58 318 734 1346 4902
1975 59 289 756 1344 4786
1976 59 302 693 1247 4859
1977 55 298 618 1358 4602
1978 49 288 623 1159 4526
1979 43 273 606 1230 4329
1980 55 228 556 1368 4413
1981 52 261 586 1305 4745
1982 53 268 553 1304 4755
1983 64 303 511 1271 4797
1984 55 285 611 1812 5110
1985 44 266 634 1713 4939
Data unavailable for 1986-1978
1979 68 251 574 1708
1999 693 1493
2000 65 255 696 1467
As may be observed from the above table, the cross section near the outfall had a maximum area of
929 sq. meter (1966, probably as a consequence of dredging the channel), compared to 696 sq.
meter according to the latest available data of 2000. Similarly, the cross section at Malancha had
once been as high as 2123 sq. meter (1952), which is recorded to be only 1467 sq. meter in 2000.
On the other hand, the outflows from the drainage areas up to the outfall have increased over the
years with the rapid urbanisation and associated paving of open lands.
The siltation of the Kultigong, unless remedied by dredging, may meet the same fate as that of the
silted up Bidyadhari, which at one time had been conveying the storm discharge of Kolkata.
Some of the cross sections of the drainage channels have been depicted in the following figures,
along with their designed sections. It may be observed that most of the channels are heavily up and
require thorough cleanup. Some figures are also provided for the cross sections of the river Kultigong
at specific locations.

3.36

3.37

3.38

Chapter Four
Hazard Analysis: Cyclone and Storm Surge
4.1. Cyclone hazard in coastal zones
Tropical cyclones are the deadliest of all natural disaster worldwide, accounting for about 64% of the
total loss of lives. The 80-100 tropical cyclones that occur worldwide each year cause, on an
average, death of 20,000 people and a total economic loss of $6-7 billion (Southern 1979). The
Indian subcontinent is the worst affected part of the world as far as the death toll associated with
tropical cyclone is concerned. Out of 9-recorded cases of heavy loss of human lives (40,000 or more)
by cyclones during the past 300 years, 7 cases (77%) occurred in Indian subcontinent (Frank and
Hussain, 1971; Smith, 1989; Hebert et al., 1996). The tropical cyclones affect this region in two
seasons: Pre-monsoon (April-May) and Post-monsoon (October-December). The peak frequency is
found to be in the months of May and November.
CHAPTER 4
The Bay of Bengal is potentially energetic for the development of cyclonic storms and accounts for
about 7% of the global annual total number of storms (Gray, 1968). These storms usually move
towards the west, northwest and north. Some of them recurve towards northeast after initial
northwestward movement. Though, considered to be much weaker in intensity and smaller in size as
compared to the cyclones of other regions, the Bay of Bengal cyclones, in particular, the post
monsoon cyclones that cross east coast of India or Bangladesh are highly devastating. This is mainly
due to dense populated coastal region, shallow bathymetry; nearly funnel shape of the coastline and
the long stretch of the low-lying delta region embedded with large number of river systems. The
casualty figures associated with major Bay of Bengal cyclones in the recent past are 3, 00,000 and 1,
31,000 in Bangladesh in 1970 and 1991 respectively; 10,000 and 1000 in 1977 and 1990
respectively in Andhra Pradesh (India) (Smith, 1989; Holland, 1993; Gupta, 1999). The super cyclone
that crossed Orissa (India) coast on 29th November 1999 affected 129.66 lakhs people (about
10,000 people killed) and caused huge damage to properties (Kalsi, 2003). After independence, the
most severe cyclone that crossed West Bengal coast was the cyclone of November 1988. Around
28.3 lacs people in 3893 villages were affected by the cyclone, killing 532 people.

4.2
In US, there is a steady decrease in the death toll caused by tropical cyclones with an average death
toll of 7,000 during 1900-1910, 1,000 during 1950-1960 to only around 200 during 1990-1995
(Southern, 1991). This is attributed to effective warning system, good response from the affected
community and proper mitigation plan. In contrast, the property damage has been increased
considerably due to increasing activity in the coastal region and increase in material and labor cost.
However, in Southeast Asia and particularly in Indian region, there is no significant decrease in loss
of life, which is being reflected by the death toll of about 1,31,000 in 1991 Bangladesh cyclone and
about 10,000 in 1999 Orissa super cyclone. At the same time, the damage to properties has been
increased sharply in last few decades.
In the present study, the past datasets about the occurrence to tropical cyclones over this region (the
Bay of Bengal cyclones in the Indian region) is analyzed to determine the locations of high hazard
incidence.
4.2. Data Analysis
As mentioned above, the vulnerability of the West Bengal coastal districts / blocks are assessed by
analyzing the past cyclone datasets. For this purpose, the 114 years (1891-2004) past cyclone
datasets obtained from India Meteorological Department (tropical cyclone Atlas and other scientific
documents & journals) and Joint Typhoon Warning Centre (JTWC, USA), are used. The datasets
used to find out the number / percentage of storms / severe storms (developed over the Bay of
Bengal) crossed various countries bordering the Bay of Bengal and storms dissipated over the
ocean. Further, the frequency of storms/ severe storms crossing various state boundary of India is
calculated.
Figure-1 shows the number and percentage of cyclones crossing Indian coast-line and coast-line of
other countries viz., Bangladesh, Myanmar, Sri Lanka and those dissipated over the ocean itself.
This clearly shows that most of the cyclones developed over the Bay of Bengal crosses Indian coast
line (60.8%), the next highest being the number of cyclones dissipated over the sea. Thus in terms of
frequency, among the countries bordering Bay of Bengal, India is most vulnerable. It is must be
mentioned here that the vulnerability due tropical cyclones cannot be determined by solely by its
frequency of occurrence, the vulnerability depends on associated storm surge, coastal inundation /
flooding and socio-economy of the possible affected region.

4.3
Figure 1: Number and percentage of tropical cyclone crossing coast-line of India, Bangladesh,
Myanmar, SriLanka and the ones dissipated over Ocean.
Figure 2: Number of tropical cyclone crossing coast-line of various states of India

4.4
This shows that Orissa (with 103 cyclones in last 114 years) is most affected state with Andhra
Pradesh (with 73 cyclones in last 114 years) is second most affected state closely followed by West
Bengal (with 71 cyclones in last 114 years). This indicates the importance of vulnerability assessment
of West Bengal due to tropical cyclones.
4.3. District-wise distribution
The above mentioned 114 year’s cyclone datasets are used to assess the vulnerability of the districts
of West Bengal. The datasets shows that only nine districts of the states are affected by one or more
cyclones during last 114 years. The figure-3 below shows the number of cyclones & severe cyclones
affected the districts.
40
35
30
25
20
15
10
5
0
.
Midnapore 24 24
Pargana(N) Pargana(S)
Haora Nadia Bankura Hugli Bardhaman Purulia
Severe Cyclone
Cyclone
Figure 3: Number of tropical cyclone crossing various districts of India
Only two coastal districts (South 24 Pargana and Midnapore or more specifically east Midnapore) are
affected by severe cyclones that too only 3 severe cyclones crossing east Midnapore. So, in that
sense only South 24 Pargana is found to be vulnerable to severe cyclones with 12 severe cyclones
crossing the district. Similar is the case for cyclones as well with 32 & 38 cyclones crossing
Midnapore and South 24 Parganas respectively. Other districts are affected by a few cyclones only.
Table 1 gives the number / frequency of cyclones and their return period in years.

4.5
Table 1: Frequency and return period of severe cyclones and cyclones on the
districts of West Bengal.
District Name
Severe Cyclones
Cyclones
Number Return Number Return Period
Period
Midnapore 3 38 32 4
North 24 Pargana 0 - 11 10
South 24 Pargana 12 10 38 3
Haora 0 - 5 23
Nadia 0 - 3 38
Bankura 0 - 9 13
Hoogle 0 - 4 28
Bardhaman 0 - 4 28
Purulia 0 - 4 28
The above table clearly shows that South 24 Pargana is the most vulnerable district with a severe
cyclone in every ten years and a cyclone in very three years. It is followed by Midnapore with a
cyclone in every four years and a severe cyclone in every 38 years. Rest of the districts is affected by
few cyclones only with return period more than 20 years. It can also be mentioned here that the
coastal area of South 24 Pargana is the low laying delta region and may results high storm surge and
coastal inundation leading to be higher vulnerability.
4.4. Block-wise distribution
West Bengal has two districts touching the Bay of Bengal; these are South 24 Pargana & East
Midnapore. And as seen in the previous section, these two districts are most vulnerable and hence,
need to be discussed further in details. Table-2 shows the coastal blocks with number of cyclones /
severe cyclones causing landfall. This shows that 12 among 15 severe cyclones and 38 among 56
cyclones causes landfall in South 24 Pargana. The return periods of the cyclones / severe cyclones
are show in the Table-3. These two tables give an overview of landfall of these storms on the West
Bengal coastline. Total 71 cyclonic storms crossed West Bengal during last 114 years, among these
26 crossed the coast-line at Gosaba. Figure 4 shows the coastal blocks of South 24 Pargana and
number of cyclones and severe cyclones crossing these blocks. This also clearly indicated Gosaba is
the most affected block in this district.

4.6
30
25
20
15
10
Severe Cyclone
Cyclone
5
0
Gosaba Kultali Patharpratima Namkhana Sagar Kakdwip
Figure 4: Number of cyclone /severe cyclones affecting the coastal blocks of South 24 Pargana
In similar manner, figure 5 shows the number of cyclones / severe cyclones affecting the coastal
blocks of East Midnapore district. And in this case, the block Ramnagar-II is the most affected block.
Also Ramnagar-II block is not as low lying as Gosaba, thus it can be noted that among the all coastal
blocks, Gosaba is the most vulnerable. The most severe cyclonic storms that crossed east coast of
India in recent years are 1988 & 1998 and both of these storms crossed the coast-line at Gosaba.
9
8
7
6
5
4
3
2
1
0
Ramnagar-I Ramnagar-II Contai-I Contai-II Khejuri-II Nandigram-I Sutahata-I Sutahata-II
Severe Cyclone
Cyclone
Figure 5: Number of cyclone /severe cyclones affecting the coastal blocks of East Midnapore.
The cyclone that crossed West Bengal coast over Gosaba at 1200 UTC of 29 November 1988 was
the most intense storm in the history of West Bengal after independence. The storm intensified into
severe cyclonic around 06 UTC 25 November. From 26 mornings onwards the storm moved a
northerly direction and headed for West Bengal-Bangladesh coast. During its northerly course it
further intensified into a core of hurricane winds on 27 mornings. It crosses West Bengal coast

4.7
around 20 km west of Bangladesh border. After crossing the coast it maintained hurricane strength
for about 6-7 hours and after that weakened rapidly. The system was one of the super storms that
affected Indian coast. The lowest central pressure recorded was 942 hPa. The furry of the hurricane
was felt over north & south 24 Parganas and some coastal districts of Bangladesh. Sagar Island
reported winds of 180 kts on 29 November.
28.29 lacs of people in 3893 villages in 24 Parganas, Midnapore, Haora, Hoogly and Nadia districts
of West Bengal was affected due to the storm. 532 people died and 57,600 cattle perished and crop
& property worth of 137.77 Crores was damaged. In Bangladesh, the cyclone killed over 2000
people.
Table 2: Cyclones and severe cyclones crossing coastal blocks in the South 24
Pargana and East Midnapore
Sl. No Blocks
1. Gosaba Six (6); 1895,1909,1919,1970,
1988, 1998
2. Kultali One (1);
1937
Number of cyclonic storms
Severe Cyclones
Cyclones
Nineteen (19);
1896,1898,1902 ,1907, ,1927, 1929
1932, 1933,1937, 1940 (2), 1942,
1946, 1947, 1956, 1963, 1967, 198
2000
Six (6);
1921, 1936, 1963, 1968, 1974, 200
3. Patharpratima One (1); 1916 One (1); 1968
4. Namkhana Two (2); 1981, 1971 Eleven (11); 1948, 1951, 1952, 195
1960, 1962, 1964, 1968, 1971 (2),
1981
5. Sagar One (1); 1936 One (1); 1946
6. Kakdwip One(1); 1901 None
7. Ramnagar-I None Six (6); 1893, 1896, 1916, 1917, 19
1961
8. Ramnagar-II Two (2); 1942, 1971 Seven (7); 1893, 1896, 1898, 1904
1925, 1956, 1976
9. Contai-I None None
10. Contai-II One (1); 1976 Three (2); 1953, 1975
11. Khejuri-II None Two (2); 1941, 1943
12. Nandigram-I None One (1); 1927
13. Sutahata None None
Total Fifteen (15) Fifty Six (56)

4.8
Table 3: Return periods of cyclones and severe cyclones crossing coastal
blocks in the South 24 Pargana and East Midnapore
Sl. Blocks
Return period
No.
Severe Cyclones
Cyclones
1. Gosaba 19 years 6 years
2. Kultali 114 years 19 years
3. Patharpratima 114 years 114 years
4. Namkhana 57 years 10 years
5. Sagar 114 years 114 years
6. Kakdwip 114 years -
7. Ramnagar-I - 19 years
8. Ramnagar-II 57 years 16 years
9. Contai-I - -
10. Contai-II 114 years 57 years
11. Khejuri-II - 57 years
12. Nandigram-I - 114 years
13. Sutahata - -
Nine districts of West Bengal get affected by cyclones. But as far as vulnerability is concerned, South
24 Pargana, East Midnapore, North 24 Pargana and Bankura have cyclone return period of less than
20 years and may be considered as vulnerable. The block-wise (of all blocks) statistics of cyclones
and severe cyclones from South 24 Pargana, East Midnapore and Haora are shown in tables 4, 5, 6
respectively.
The East Midnapore and South 24 Pargana are the two most vulnerable districts with cyclone return
periods of four and three years respectively. In East Midnapore district, eleven blocks, viz.,
Ramnagar-I, Ramnagar-II, Contai-I, Contai-II, Contai-III, Nandigram-I, Nandigram-II, Egra-I, Egra-II,
Pataspur-I and Pataspur-II have cyclone return period of less than 20 years and may be considered
as vulnerable. Seven blocks (Gosaba, Kultali, Namkhana, Patharpratima, Sagar, Diamond Harbour-I
and Basanti) of South 24 Pargana are vulnerable as far as cyclone frequency is concern.
Eleven blocks (Ramnagar-I, Ramnagar-II, Contai-I, Contai-II, Contai-III, Nandigram-I, Nandigram-II,
Egra-I, Egra-II, Pataspur-I and Pataspur-II) can be termed as vulnerable to cyclonic storms.

4.9
Table 4: The number and return period of cyclones and severe cyclones that affected the
blocks of South 24 Pargana District
Block Name
Severe Cyclones
Number Return
Period
Cyclones
Number Return
Period
Gosaba 6 19 25 5
Kultali 1 114 15 8
Patharpratima 1 114 11 10
Namkhana 2 57 14 8
Sagar 1 114 12 10
Kakdwip 1 114 4 28
Kulpi 0 - 4 28
Mathurapur-I 0 - 4 28
Mathurapur-II 0 - 3 38
Mandirbazar 0 - 3 38
Diamond Harbour-I 0 - 6 19
Diamond Harbour-II 0 - 2 57
Mograhat-I 0 - 3 38
Mograhat-II 0 - 2 57
Jaynagar-I 0 - 1 114
Jaynagar-II 0 - 1 114
Basanti 0 - 9 13
Canning-I 0 - 4 28
Canning-II 0 - 2 57
Baruipur 0 - 5 23
Bhangar-I 0 - 2 57
Bhangar-II 0 - 5 23
Sonarpur 0 - 5 23
Falta 0 - 3 38
Bishnupur-I 0 - 1 114
Bishnupur-II 0 - 1 114
Budge Budge-I 0 - 1 114
Budge Budge-II 0 - 2 57

4.10
Table 5: The number and return period of cyclones and severe cyclones that affected the
blocks of East Midnapore District
Block Name
Severe Cyclones
Cyclones
Number Return Number Return Period
Period
Ramnagar-I 0 - 7 16
Ramnagar-II 2 57 8 14
Contai-I 0 - 6 19
Contai-II 1 114 7 16
Contai-III 0 - 8 14
Khejuri-I 0 - 2 57
Khejuri-II 0 - 4 28
Nandigram-I 0 - 6 19
Nandigram-II 0 - 6 19
Nandigram-III 0 - 4 28
Sutahata-I 0 - 1 114
Sutahata-II 0 - 3 38
Mahisadal 0 - 3 38
Nandakumar 0 - 4 28
Tamluk 0 - 3 38
Sahid Matangini 0 0 -
Egra-I 0 - 9 13
Egra-II 0 - 11 10
Pataspur-I 0 - 9 13
Pataspur-II 0 - 11 10
Bhagawanpur-I 0 - 3 38
Bhagawanpur-II 0 - 5 23
Mayna 0 - 1 114
Panskura-I 0 - 1 114
Panskura-II 0 - 2 57

4.11
4.5. Assessment of Storm surge
Storm surge is a phenomenon where the tide level rises mainly due to drifted seawater and a drop in
atmospheric pressure when a low pressure system approaches. The hazard level of storm surge
inundation is assessed by estimating the seawater inflow due to storm surges in the assessment
area and the depth of inundation and other factors which are used as indices of damage.
The east coast of India is frequently affected by storm surges. Most vulnerable portions of the east coast
are Orissa, West Bengal and south Andhra coasts. To cite some of the destructive cyclones over the
Bay of Bengal are 1977 Andhra Cyclone, 1999 Orissa Super cyclone, 1970 Bhola cyclone etc., where
reported loss of lives are enormous. In recent past, the loss of life is considerably reduced compared to
the earlier extreme events. The reason is improvement in the forecasting methods and timely evacuation
of people from the vulnerable areas. There can be little doubt that the number of causalities would have
been considerably lower if the surge could have been predicted, say, 24 hours in advance allowing
effective warnings in the vulnerable areas. The prediction, must, of course, be accurate enough so that
one can distinguish between the dangerous surges and the surges that cause little harm, as people
can not be evacuated from the exposed areas for every approaching storm. To note, success have
been achieved in predicting storm surges through operational numerical models.
Operational numerical storm surge prediction models have been developed and are being routinely used
for several coastal regions of the world such as: Storm Tide Warning Service (STWS) in the UK;
operational systems in the Netherlands and National Marine Environmental Forecasting centre in China.
A review of these operational forecasting system models is given in Jiping et al.(1990), Jelesnianski
(1989), Murty (1984) and Sundermann and Lenz (1983). The development of operational numerical
storm surge prediction system in India is an active thrust area which needs immediate attention, where
most of these models require large computational resources. Hence, for routine forecasting of storm
surges providing multiple forecast scenarios, the models cannot be used in the absence of adequate
computing facility. To overcome this difficulty, most of the forecasting offices including India
Meteorological Department (IMD) use the nomogram method for prediction of storm surges
associated with tropical cyclones. These nomograms are produced based on sensitivity analysis of
modeling studies conducted for varied bathymetries and approach angles.
The second WMO International workshop on tropical cyclones recommended the use of personal
computers (PCs) by the developing countries in order to adopt the stand-alone storm-surge forecasting
system. Recent advent of powerful personal computers has opened up the possibility of running
dynamical models in real time on PC-based work stations in an operational office. In fact, a PC-based

4.12
work station (the Automated Tropical Cyclone Forecasting System, ATCF) is already in operation
at the Joint Typhoon Warning Centre, Guam for the past many years. The Australian Bureau of
Meteorological Research Centre, together with their Bureau of Severe Weather Programme Office has
also developed a work station based model for storm surge forecasting.
Mechanics of the Storm Surge
In the Bay of Bengal area itself 142 moderate to severe storm surge events are on record from 1582 to
1991. These surges, some in excess of eight meters (26 ft.), have killed hundreds of thousands of
people, primarily in Bangladesh (Murty and Flather, 1994). At least five processes can be involved in
altering tide levels during storms. These include the pressure effect, the direct wind effect, the effect of
the earth's rotation, the effect of waves, and the rainfall effect (Harris, 1963). The pressure effects of a
tropical cyclone will cause the water level in the open ocean to rise in regions of low pressure and fall in
regions of high pressure. Wind stresses causes a phenomenon referred to as "wind set-up”, which is the
tendency for water levels to increase at the downwind shore, and to decrease at the upwind shore that is
inversely proportional to depth. Wind set-up on an open coast will be driven into bays in the same way
as the astronomical tide.
Surge and wave heights on-shore are directly governed by the configuration and bathymetry of
the sea-bottom. For narrow shelf (one that drops steeply from the shoreline and subsequently produces
deep water in close proximity to shoreline) tends to produce a lower surge, but a surface wave of higher
magnitude. The situation is continental shelf region along the eastern belt of India is gently sloping and
quite wide compared with the west coast which results in higher surges along east coast compared to
the west coast. In deeper waters, a surge can be dispersed away from the cyclone. Upon entering a
shallow gently sloping shelf, the surge cannot be dispersed away, but is generally driven onshore by the
wind stress associated with the tropical cyclone. In the immediate vicinity of near-shore area, topography
of land surface is another important element in determining the storm surge extent. Areas where the land
areas like less than a few meters above mean sea-level are at particular risk from storm surge
inundation.
4.6. Bottom Characteristics in Bay of Bengal
The Bay of Bengal is the northward extended portion of the Indian Ocean. It is located between latitudes
5°N - 22°N and 80°E - 100°E longitudes. Westward it is bounded by the East coast of Sri Lanka and
India, on north by the deltaic region of the Ganges-Brahmaputra-Meghna river system, and on the east
by the Myanmar peninsula extended upto the Andaman-Nicobar ridges (Figure – 1). The southward
boundary of the Bay is approximately along the line drawn from Dondra Head in south of Sri Lanka to

4.13
the northern tip of Sumatra. The Bay occupies an area of about 2.2 million square kilometers with an
average depth of 2,600 meters and maximum of 5,260 meters.
Figure - 6: Bottom relief feature – Bay of Bengal
4.6.1. Bottom Topography
The bottom topography is characterized by broad funnel shaped basin with southward limit to the Indian
Ocean. A thick uniform abyssal plain occupies almost the entire Bay of Bengal gently sloping southward
at an angle of approximately 8°-10°. In many places underwater valleys dissect this plain continental
mass. The width of the continental shelf varies considerably approximately less than 100 Kilometers.
The “Swatch of No Ground” typically known as ‘Ganga Trough’ has a comparatively flat floor roughly 5 to
7 kilometer wide and walls of about 12°inclination. This area has a seaward continuation for almost 2000
kilometers down the Bay of Bengal in form of fan valleys. Sandbars and ridges near the mouth of the
Ganges-Brahmaputra delta pointing towards the ‘Swatch of No Ground” show sediments are tunneled

4.14
through this trough into the deeper part of the Bay of Bengal. The shallower part of southern continental
shelf off the coast of the Sunderbans, Patuakhali and Noakhali is covered by silt and clay, and extensive
muddy tidal flats are developed along the shoreline. The ‘Sunda Trench’ runs parallel along the
Westside of the Andaman-Nicobar islands which extends northward upto 10°N into the Bay and joins the
eastern limit of the Himalayan range. The ‘Ninety East ridge’ runs in a north-south direction
approximately along the 90°E longitude which lie immediately outboard the Sunda trench between the
Bengal fan and the Nicobar fan.
4.6.2. Hydrological and Oceanographic characteristics
The hydrological conditions in the Bay of Bengal are determined by the monsoonal wind system and
also by hydrological characteristics of the open part of Indian Ocean. Discharge of fresh water from
rivers largely influences the coastal northern part of the Bay. Physical oceanographic parameters
pertaining to temperature, salinity and density of water in the southern part of the Bay of Bengal is similar
to the open ocean. In the coastal region of the Bay and in north-eastern part of the Andaman Sea where
significant influence of river water is present, the temperature and salinity are found different from the
open part of the Bay.
4.6.3.Temperature
The mean annual temperature of the surface water is about 28°C. The maximum temperature is
observed in May (approx. 30°C) and minimum of 25°C in January-February month. The variation in
temperature is about 2°C in the southern end and about 5°C in the northward limits of the Bay of
Bengal.
4.6.4. Salinity
In the open part of the Bay the salinity varies from 32‰ to 34.5‰, and in coastal region the variation is
from 10‰ to 25‰. At the river mouths, the surface salinity decreases to 5‰ or even less. The coastal
water is significantly diluted throughout the year, although the river water is greatly reduced during
winter. Along the Ganges-Brahmaputra deltaic region there is decrease in salinity about 1‰ during
summer which increases to 15‰ - 20‰ in winter. Salinity variations increase from the coast towards the
open part of the Bay. On a vertical scale, the influence of fresh water discharge is experienced up to
depths of 200 – 300 meters

4.15
4.6.5. Tides
The Head Bay region experiences semi-diurnal type of tides (two high and two low tides in a period of 24
hours and 52 minutes). The highest tide is seen where the influence of bottom relief and configuration of
the coast are prominent, in immediate vicinity of shallow water bays and estuarine confluence. The
average height of tidal wave in the deltaic coast of the Ganges is about 4.92 meter. The tidal currents
are strong which develop in the mouths of the rivers like the Hooghly and Meghna. The tidal information
at six locations in the Hooghly River is depicted in Table -1.
Table -6: Tide Table for the Hooghly River
SAGAR GANGRA HALDIA
DIAMOND
HARBOUR MAYAPUR
GARDEN
REACH
Highest High Water 6.66 7.25 7.26 7.35 7.1 7.7
Mean H.W. Spring
Freshlets 5.49 5.84 5.92 6.22 5.88 6.12
Mean High water
Springs Dry Season 5.06 5.43 5.51 5.74 5.28 5.24
Mean High water
Springs 5.22 5.6 5.7 5.94 5.54 5.62
Mean High Water 4.64 4.93 5.01 5.24 4.83 4.88
Mean High water
Neaps Freshlets 3.98 4.31 4.43 4.62 4.29 4.45
Mean High water
Neaps Dry season 3.75 3.97 4.08 4.3 3.76 3.79
Mean High water
Neaps 3.86 4.12 4.26 4.42 3.98 4.1
Local Mean water level 3 3.16 3.23 3.3 3 3.19
Mean Low water
Neap Freshlets 2.42 2.31 2.28 2.36 2.04 2.38
Mean Low water Neaps
Season 2.11 1.93 1.93 1.96 1.57 1.76
Mean Low water
Neaps 2.23 2.09 2.1 2.14 1.78 2

4.16
Mean Low water 1.51 1.39 1.34 1.47 1.28 1.68
Mean Low water
Springs Freshlets 1.03 0.89 0.87 0.96 1 1.65
Mean Low water
Springs Dry Season 0.84 0.77 0.75 0.93 0.85 1.22
Mean Low water
Springs 0.92 0.83 0.8 0.94 0.91 1.41
SITE OF TIDAL OBSERVATORIES:
Station: SAGAR
(LAT: 21 39'N, 88 03'E)
Station: GANGRA
(LAT: 21 57'N, 88 01'E)
Station: HALDIA
(LAT: 22 02'N, 88 06'E)
Station: DIAMOND HARBOUR
(LAT: 22 12'N, 88 10'E)
Station: MAYAPUR
(LAT: 22 26'N, 88 08'E)
Station: GARDEN REACH
(LAT: 22 33'N, 88 18'E)
The tidal amplification is remarkably seen when approaching from the tidal observatory of Sagar to
Garden Reach.
4.6.6. Sea Level
The influence of sea-water density and wind on sea-level shows a seasonal change in the Head Bay
region. The range at Khidirpur is 166 cm, at Kolkata about 130 cm while at Chittagong is about 118 cm.
In open waters of the eastern belt, the range is small compared to the northern and north-eastern coasts
of the Bay.
4.6.7. Surface and Sub-surface Current
The surface circulation is found to be generally clockwise from January to July and counter-clockwise
from August to December, which is analogous to the reversible monsoonal wind system. The flow is not

4.17
constant, but depends on the strength and duration of the winds. The effects of strong wind blowing for a
few consecutive days are reflected in the rate of flow. Currents to the north-east generally persist longer
and flow at greater speed because of the stronger south-west monsoons. The vertical circulation in the
Bay of Bengal is the upwelling/downwelling process which is almost seasonal in nature.
4.7. Mathematical Formulation of Storm Surge
In the formulation of the model, the sphericity of the earth's surface is ignored. A system of rectangular
Cartesian coordinates is used in which the origin, O, is in the equilibrium level of the sea surface. Ox
points towards the east, Oy points towards the north and Oz is directed vertically upwards. The
displaced position of the free surface is given by z =ζ (x,y,t) and the position of the sea floor by z = −
h(x,y). Under these conditions, the basic hydrodynamic equations of continuity and momentum for the
dynamical process in the sea may be given by
∂u
∂x
∂v
+
∂y
∂w
+ = 0
∂z
(1)
∂u
∂u
∂u
∂ u
+ u + v + w −
∂t
∂x
∂y
∂z
fv =
1 ∂p
1 ∂τ
x
+
ρ ∂x
ρ ∂z
(2)
∂v
∂t
+
u
∂ v
∂x
+
v
∂v
∂y
+
w
∂v
∂z
+
fu
=
−
1 ∂p
ρ ∂y
+
1 ∂τ
ρ ∂z
y
(3)
∂w
+ u
∂t
∂w
∂w
∂w
+ v + w
∂x
∂y
∂z
1 ∂p
= −
ρ ∂z
− g
(4)
where,
u,v,w : Renolds averaged component of velocity in the direction of
x,y, and z respectively,
t : time,
p : pressure,
ρ : density of seawater assumed homogenous and incompressible,
f : Coriolis parameter, f = 2ωsinφ
g : acceleration due to gravity,

4.18
τx,τy : x and y components of the frictional stress.
Molecular viscosity has been neglected in these equations. The terms τx and τy are included to model
vertical turbulent diffusion. Denoting the wind stress and bottom stress components as (FS,GS) and (FB,
GB) respectively and the surface pressure as pa, the boundary conditions become,
u = v = w= 0
at z = -h
( y
τ x , τ ) = ( F B , G B)
at z = -h (5)
( y
τ x , τ ) = ( F s , G s)
at z = ζ
p = pa
at z = ζ
∂ζ
∂ζ
∂ζ
+ u + v = w
∂t
∂x
∂y
at z = ζ (6)
Here, the last condition is the kinematic surface condition and expresses the fact that the free surface is
materially following the fluid. For long period waves, it is reasonable here to assume that wave length is
large compared to the water depth. Using this assumption, it may be shown (Welander, 1961) that
equation (4) reduces to the hydrostatic pressure approximation
∂p
=- ρg
∂z
(7)
The principal equations (1), (2), (3) and (7) could be solved, but the procedure would be laborious
because of the presence of the vertical coordinate. Unlike problems of the atmosphere, a boundary layer
would need to be designed both at the top and bottom of the domain of integration. There is insufficient
knowledge about the flow in such boundary layers.
To get over this difficulty, a simplification is generally introduced by integrating the governing equations
in the vertical. The unknown dependent variables are then (a) the water transport (or mean current) and
(b) the surface height. This procedure has commonly been adopted for storm surge computations

4.19
because the water level is of primary importance. Integrating (1) to (3) in the vertical from z = − h to z = ζ
and using conditions (5) to (7) one gets:
∂ζ
∂
∂
+ [( ζ + h)
u] + [( ζ + h)
v] = 0
∂t
∂x
∂y
(8)
∂u
∂u
∂u
1 ⎡ ∂
2
2
∂
⎤
+ u + v − f v+
⎢ ( ζ + h)(
u -u
) + ( ζ + h)(
uv−uv)
⎥
∂t
∂x
∂y
( ζ + h)
⎣∂x
∂y
⎦
∂ζ
1 ∂pa
1
= −g
− + [ Fs−FB]
∂x
ρ ∂x
( ζ + h)
ρ
(9)
∂v
∂v
∂v
1 ⎡ ∂
∂
+ u + v + f u + ⎢ ( ζ + h)(
uv−u v)
+
∂t
∂x
∂y
( ζ + h)
⎣ ∂x
∂y
∂ζ
1 ∂pa
1
=- g − + [ Gs
−GB]
∂y
ρ ∂y
( ζ + h)
ρ
2 2
⎤
( ζ + h) ( v −v
) ⎥
⎦
(10)
where: over bars denote the depth averaged values, e. g.,
1
( u,
v)
=
( ζ + h)
ζ
∫
- h
( u,
v)d
z,
(11)
ζ
2
(
2 2
1
2
u , v ) = ( u , v )d z,
( ζ + h)
∫
- h
(12)
1
( uv)
=
( ζ + h)
ζ
∫
- h
uv
d z,
(13)
In most of the storm surge simulation models, the non-linear advective terms have been neglected
mainly on the basis of scale analysis. This is justifiable when the characteristic amplitude of the surge is
smaller than the characteristic depth of the basin. But in shallow water regions, particularly at the head of
the Bay of Bengal, the non-linear terms are of special importance and must be retained in the

4.20
formulation. However, the retention in (9) of terms such as
( u
2
, u
2
)
leads to a fundamental difficulty
as they can not be evaluated within the framework of a vertically integrated model. In many well -
documented applications of non-linear vertically integrated equations (8) to (10), it is usual to make
assumptions typified by:
2 2
( u − u
) = 0 ,
2 2
( v − v
) =
0 ,
(14)
( uv − uv ) =
0
u
and
v
This is equivalent to saying that the currents do not vary significantly in the vertical and the flow
is dominated by the midstream flow. The validity of the assumption (14) has been demonstrated by
Nihoul (1975) and Johns (1981). In the latter work it has been found that
2 2
(
u / u )

4.21
G
B
2 2
= - 5 c f F S + c f ρv(
u + v ) 2
2
1
(17)
It may appear surprising that the surface stress is also included in (17). This is because sea -bed friction
is largely determined by the current profile above the sea-bed which, in turn, is dependent on the vertical
gradient of the current near the surface.
However, substituting the values from (14) and (16) into the equations (9) and (10), we get (the over bars
have been dropped for convenience)
∂u
∂t
∂u
∂u
∂ζ
1 ∂p
u + v −f
v = −g
−
∂x
∂y
∂x
ρ ∂x
1 ⎡FS
+ ⎢ −c
( ζ + h)
⎣ ρ
1
2 2
⎤
u(
u + v ) ⎥
⎦
a
+ f
2
(18)
∂v
∂t
∂v
∂v
∂ζ
1 ∂p
u + v + f u = −g
−
∂x
∂y
∂y
ρ ∂y
1 ⎡GS
+ ⎢ −c
( ζ + h)
⎣ ρ
1
2 2
⎤
v(
u + v ) ⎥
⎦
a
+ f
2
(19)
For numerical treatment, it is convenient to express equations (18) and (19) in flux form as
∂
∂t
∂
∂
[ ( ζ + h)
u] + [( ζ + h)
uu] + [( ζ + h)
uv]
− f ( ζ + h)
v =
∂x
∂y
∂ζ
1 ∂ p
1
a F S
2 2
- g ( ζ + h)
− ( ζ + h)
+ − c f u ( u + v ) 2
∂x
ρ ∂x
ρ
(20)
∂
∂t
∂
∂
[ ( ζ + h)
v]+
[( ζ + h)
uv]+
[( ζ + h)
vv]+
f ( ζ + h)
u =
∂x
∂y
∂ζ
1 ∂ p
1
a GS
2 2
− g ( ζ + h)
− ( ζ + h)
+ − c v ( u + v ) 2
f
∂y
ρ ∂y
ρ
(21)
The equations (8), (20) and (21) can be written for the sake of simplicity as
∂ζ ∂u~
∂v~
+ + = 0
∂t
∂x
∂y
(22)

4.22
∂u
~ ∂
~
~ ∂ ~ ~ ∂ζ
1 ∂p
u
)+ ( ) =
a Fs
cf
2 2
+ ( uu vu −fv
−g(
ζ + h)
− ( ζ + h)
+ − ( u + v)
∂t
∂x
∂y
∂x
ρ ∂x
ρ ( ζ + h)
1
2
(23)
∂v
~ ∂
~
~ ∂ ~ ~ ∂ζ
1 ∂p
v
)+ ( )+ =
a Gs
cf
2 2
+ ( uv vv fu −g(
ζ + h)
− ( ζ + h)
+ − ( u + v )
∂t
∂x
∂y
∂y
ρ ∂y
ρ ( ζ + h)
1
2
(24)
where
u ~ = ( ζ + h)
u and v~ = ( ζ + h)
v
are the new prognostic variables and (ζ+h) gives the total
depth of the basin.
The equation of continuity (22) along with the two momemtum equations (23) and (24) form the three
basic equations of the numerical model. It consists of a set of three coupled equations for the unknowns
u, v and ζ. The forcing terms in these three equations arise out of (i) Coriolis terms, (ii) the inverted
barometric effect i.e.
∂ p
∂x
a
∂ p
and
∂y
a
due to fall in atmospheric pressure, (iii) the component of wind
stress ( FS, GS) and (iv) the bottom stress component. ( FB, GB).
If these forcing terms could be specified by meteorological data and the geometry of the continental shelf
then the problem would be solved by numerical integration. The response in the sea at any instant t > 0
then determines the surge heights.
Before proceeding to the numerical integration, it is necessary to have certain boundary and initial
conditions.
4.8. Boundary and Initial conditions
In addition to the fulfillment of the surface and bottom conditions (5) and (6), appropriate conditions have
to be satisfied along the lateral boundaries of the sea area under consideration for all time. Theoretically
the only boundary condition needed in the vertically integrated system is that the normal transport vanish
at the coast, i.e.,
u cosα
+ v sinα
= 0
for
all
t ≥ 0
(25)
where α denotes the inclination of the outward directed normal to the x-axis. It then follows that u = 0
along the y-directed boundaries and v = 0 along the x-directed boundaries.

4.23
At the open-sea boundary, the normal currents across the boundary may be prescribed, yielding a
condition such as (25) modified by a non-zero term on the right hand side of the equation. Alternatively,
a radiation type of condition may be applied, which leads to (Heaps, 1973)
⎛ g
u cosα
+ v sinα
+ ⎜
⎝ h
⎟
⎠
⎞
1
2
ζ = 0
(26)
Application of a radiation type of condition (26) at the open sea boundary of a model allows the
propagation of energy (disturbances) only outwards from the interior in the form of simple progressive
waves. It also helps to eliminate the transient response more quickly as a result of the frictional
dissipation in the system. Concerning its effectiveness Flather (1976a) notes that application of a
radiation condition in the numerical model may remove the unrealistically large currents and grid scale
oscillations in the vicinity of the open boundary which may possibly be produced by the application of
conventional open-sea boundary condition (i.e., ζ= 0 at y=0).
As usual it is assumed that the motion in the sea is generated from an initial state of rest, so that
ζ = u= v= 0 everywhere for t = 0. (27)
4.8.1. Determination of forcing functions
The forcing terms in the prediction equations (22)-(24) are the Coriolis force, the surface pressure, wind
stress components and the seabed friction. The surge is generated by an idealized cyclone, of constant
strength, tracking across the analysis area with constant speed. In view of the strong associated winds
and consequently high values of the wind stress forcing, the forcing due to barometric changes (i.e.)
∂ p
∂x
a
and
∂ p
∂y
a
may be neglected in the surge prediction models. Further, the Coriolis force can be determined by
knowing the latitudinal position of the area and the bottom stress may be parameterized in terms of
depth averaged currents by a quadratic law. The problem thus remains to compute the surface winds
and the wind stresses.
So far no good theory exists on which a computation of the surface winds can be based. A number of
numerical models use the model storms in which the wind speed is related to the pressure gradient. The
pressure field is specified by:

4.24
Δ p
p(r) = p( ∞)
−
[1+ (r/R )
2 1 / 2
]
(Isozaki, 1970) (28)
Δ p
p(r) =1010 −
2
[1+ (r/R ) ]
(Das et al., 1974) (29)
p(r) = p( ∞)
−Δ p exp ( −r/R)
(John and Ali, 1980) (30)
where, p (r) and p (∞) represent sea level pressure at r and at the cyclone periphery, R is the radius of
maximum winds and Δp is the pressure drop.
The wind distribution in the cyclone is then calculated from the cyclostrophic wind or gradient wind
formula. The cyclostrophic wind corresponding to the pressure field given by (29) is:
V
2
= 4V
2
m
2
2 2
[ μ ÷ (1+ μ ) ]
where, μ = r/R and Vm is the maximum wind at R. The maximum wind (in knots) and the pressure drop
(mb) may be related by:
1
V 2
m = C ( Δ p)
(32)
where, “C” is a numerical constant.
Johns and Ali (1980) use the following gradient wind formula for computing the wind distribution
corresponding to the pressure field (30):
(31)
V = −
fr
2
⎡f
r
+ ⎢
⎣ 4
1
2 2
2
r ∂ p⎤
+ ⎥
ρ
a
∂ r ⎦
where, ρa is the density of the air, taken as 1.293 kg m-3.
(33)
A number of other cyclone models compute the wind field by one of the following expressions:
V = V
m
⎛
⎜
⎝
r
R
3
2
⎞
⎟
⎠
, 0
≤ r ≤ R
, (Jelseninanski, 1965) (34)
V = V
m
⎛ R ⎞
⎜ ⎟
⎝ r ⎠
1
2
,
r > R
, (35)

4.25
⎛ 2Rr
⎞
V = Vm
⎜
2 2
⎟
⎝ R + r ⎠
(Jelesnianski, 1972) (36)
With the surface winds estimated one can proceed to the computation of the stress at the sea surface.
The surface stress is expressed by conventional quadratic law as:
2
F S ρ c u ( u + v
2
=
a D a a a
)
1
2
1
2
= ) 2
a D a a a
2
G S ρ c v ( u + v
where, ua and va are the x and y components of surface wind, cD is the drag coefficient. Observational
studies suggest that the drag coefficient may be related to the wind speed by:
(37)
cD = (1.00 + 0.07 v10 ) x 10-3 (38)
in which v10 is the wind speed at 10m from the mean sea level. This expression is generally valid for
wind speed less than 14 m sec-1. At wind speeds between 10 and 30 m sec-1 , cD varies from 2 x 10-
3 to 3 x10-3 with no significant dependence on wind speed. Most of the workers use a uniform value of
drag coefficient (Cd=2.8 x 10-3).
4.9. Case Studies of Storm Surges in coastal belt of West Bengal
Storm surges associated with tropical cyclones having their landfall in the coastal belt of West Bengal
distributed in block-wise for the period 1891-2005, is depicted in Table-2. The block-wise frequency of
these cyclones has been grouped based on their severity based upon the central pressure drop (∆P)
while approaching the littoral belt of West Bengal state. As noticed from Table-2, the frequency of severe
cyclones was highest in the Gosaba block with six severe extreme events in a total of 20 cases. Based
on severe cyclones, the other blocks following Gosaba are Namkhana and Ramnagar which
experienced two severe cyclones. Accordingly, four severe cyclones were selected viz; 1998 Gosaba
cyclone, 1988 Gosaba cyclone, 1981 Namkhana cyclone and 202 Kultali cyclone. Among these four
extreme events, the 1988 Gosaba cyclone was considered the most severe.
Case -1: 1998 Gosaba Cyclone
The track and computed surge for the 1998 Gosaba cyclone is depicted in Figure-2(a). The simulation
run was performed for 16 hours prior to the cyclone making its landfall off Gosaba. The computed

4.26
maximum surge for this event was 6.97 meter. Twelve (12) offshore locations were selected in the
present study, four of which are in the vicinity of West Bengal and remaining in the Bangladesh. The
radius of maximum winds (R) for this event is approximately 40 kilometer with a pressure drop (ΔP) of
60 millibar. The computed surge along pre-defined location in the coastal West Bengal show a maximum
surge of 4.11 m off Patharprathima. In the immediate vicinity far east off Sunderbans, the computed
surge is 3.31 meters along New Moore Islands. Left of this track along Bakhali the computed surge is
3.81 m. The computed U and V components of velocity pertaining to surface currents are shown in
Figures-2b,c. It could be noticed a strong north-west component of current existed during this event.
Case -2: 1988 Gosaba Cyclone
Figure-3(a) show the track and computed surge for the 1988 Gosaba cyclone. The simulation for this
event was performed for 13 hours before the cyclone made its landfall off Gosaba. The computed
maximum surge for this event was 11.26 meter. In this study, twelve (12) offshore locations were
selected, four of which are in the coastal belt of West Bengal and the rest in Bangladesh. The radius of
maximum winds (R) is approximately 50 kilometer with a maximum pressure drop (∆P) of 71 millibar.
This event was considered the most severe in the past 113 years making landfall in this block. In the
vicinity far east Sunderbans (Moore Is., Station-4) the computed surge is 2.18 meter, whereas
immediate vicinity right of this track maximum computed surge was 4.78 meter off Bakhali. The
computed surge off Patharprathima was approximately 3.72 meter. The computed U and V components
of the surface currents are shown in Figures-3b,c. The surface currents exhibit strong easterly
component in the coastal belts of West Bengal having spatial variability of approximately 300 kilometers,
whereas east of Sunderbans the currents noticed were in the north-westerly direction.
Case -3: 1981 Namkhana Cyclone
The computed surge and track for the 1982 Namkhana cyclone is shown in Figure-4(a). The simulation
run for this event was performed for 21 hours. The radius of maximum winds was 60 Kilometer and
∆P=37 millibar. The computed maximum surge for this event was 4.47 meter. Figures-4b,c show the U
and V components associated with this event where the resultant currents are dominant easterly.
Case -4: 2002 Kulthali Cyclone
Figure-5(a) show the computed surge and track associated with this cyclone. The maximum surge for
this event is 3.5 meter. The radius of maximum winds and maximum pressure drop are 25 kilometer and
29 millibar respectively. The simulation run for this event before its landfall was made for 11 hours. From

4.27
Figures-5b,c which show the U and V components of the computed surface velocities, strong northeasterly
currents are seen prevailing during this event.
The frequency of cyclones in coastal blocks of West Bengal is shown in Figure-6 and the vulnerability of
four pre-defined locations viz; East Bakhali, Bakhali, Patharpratima and Moore Is. are depicted in Figure-
7. Though the frequency as seen from Figure-6 is higher in the Gosaba block, the vulnerability risk is
higher in Bakhali compared with other three locations.
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# # ############### # ############ ### # # # # # # ############### # ############ ### # # # # # # ############### # ############ #### # # # # # # ############# # ############ #### # # # # # # ############# # #####
# # ############### # ############ ### # # # # # # ############### # ############ ### # # # # # # ############### # ############ #### # # # # # # ############# # ############ #### # # # # # # ############# # #####
# # ############### # ############ ### # # # # # # ############### # ############ ### # # # # # # ############### # ############ #### # # # # # # ############# # ############ #### # # # # # # ############# # #####
# # ############### # ############ ### # # # # # # ############### # ############ ### # # # # # # ############### # ############ #### # # # # # # ############# # ############ #### # # # # # # ############# # #####
# # ############### # ############ ### # # # # # # ############### # ############ ### # # # # # # ############### # ############ #### # # # # # # ############# # ############ #### # # # # # # ############# # #####
# # ############### # ############ ### # # # # # # ############### # ############ ### # # # # # # ############### # ############ #### # # # # # # ############# # ############ #### # # # # # # ############# # #####
# # ############### # ############ ### # # # # # # ############### # ############ ### # # # # # # ############### # ############ #### # # # # # # ############# # ############ #### # # # # # # ############# # #####
#
#
#
#
#
#
#
#
#
#
#Y #Y #Y #Y #Y #Y #Y #Y #Y #Y #Y#Y
INDIA
BANGLADESH
MYANMAR
Cyclone Track
1 2
3 4 5 6 7 8 9 10 11 12
Station-1: 0.30 m
Station-2: 3.81 m
Station-3: 4.11 m
Station-4: 3.31 m
Station-5: 2.44 m
Station-6: 1.46 m
Station-7: 1.16 m
Station-8: 0.73 m
Station-9: 0.40 m
Station-10: 0.08 m
Station-11: 0.0 m
Station-12: 0.0 m
Storm surge computed at pre-defined locations along
Stations: 1-12 in coastal belt of West Bengal
Figure 7: Track and computed surge for 1988 Gosaba cyclone

4.28
U-Component of Velocity (Surface currents)
INDIA
BANGLADESH
MYANMAR
#######################################################################################################################################################
#######################################################################################################################################################
#######################################################################################################################################################
#######################################################################################################################################################
#######################################################################################################################################################
#######################################################################################################################################################
#######################################################################################################################################################
#######################################################################################################################################################
#######################################################################################################################################################
Country.shp
Sort-uc1.txt
# -2.325 - -0.831
# -0.831 - -0.432
# -0.432 - -0.257
# -0.257 - -0.161
# -0.161 - -0.062
# -0.062 - 0.124
# 0.124 - 0.378
# 0.378 - 0.623
# 0.623 - 1.127
# 1.127 - 2.707
Figure - 8: U-component of velocity for 1988 Gosaba cyclone

4.29
V-Component of Velocity (Surface currents)
INDIA
BANGLADESH
MYANMAR
#######################################################################################################################################################
#######################################################################################################################################################
#######################################################################################################################################################
#######################################################################################################################################################
#######################################################################################################################################################
#######################################################################################################################################################
#######################################################################################################################################################
#######################################################################################################################################################
#######################################################################################################################################################
Country.shp
Sort-vc1.txt
# -1.58 - 0.054
# 0.054 - 0.187
# 0.187 - 0.318
# 0.318 - 0.439
# 0.439 - 0.543
# 0.543 - 0.702
# 0.702 - 0.935
# 0.935 - 1.334
# 1.334 - 2.028
# 2.028 - 3.186
Figure - 9: V-component of velocity for 1988 Gosaba cyclone

4.30
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4.31
U-component of Velocity (Surface currents)
BANGLADESH
INDIA
#######################################################################################################################################################
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Country.shp
Sort-uc1.txt
# -1.727 - -1.002
# -1.002 - -0.657
# -0.657 - -0.467
# -0.467 - -0.313
# -0.313 - -0.2
# -0.2 - -0.075
# -0.075 - 0.215
# 0.215 - 0.622
# 0.622 - 1
# 1 - 1.857
Figure - 11: U-component of velocity for 1998 Gosaba cyclone

4.32
V-component of Velocity (Surface currents)
BANGLADESH
INDIA
#######################################################################################################################################################
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Country.shp
Sort-vc1.txt
# -2.082 - 0.047
# 0.047 - 0.188
# 0.188 - 0.311
# 0.311 - 0.452
# 0.452 - 0.627
# 0.627 - 0.837
# 0.837 - 1.114
# 1.114 - 1.452
# 1.452 - 1.979
# 1.979 - 2.837
Figure - 12: V-component of velocity for 1998 Gosaba cyclone

4.33
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INDIA
MYANMAR
BANGLADESH
Figure - 13: Track and computed surge for November 2002 Kultali
Cyclone

4.34
U-component of Velocity (Surface currents)
INDIA
BANGLADESH
#######################################################################################################################################################
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Country.shp
Sort-uc1.txt
# -0.835 - -0.406
# -0.406 - -0.122
# -0.122 - -0.053
# -0.053 - -0.015
# -0.015 - 0.032
# 0.032 - 0.106
# 0.106 - 0.192
# 0.192 - 0.283
# 0.283 - 0.413
# 0.413 - 0.765
Figure - 14: U-component of velocity for 2002 Kultali cyclone

4.35
V-component of Velocity (Surface currents)
INDIA
BANGLADESH
#######################################################################################################################################################
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Country.shp
Sort-vc1.txt
# -0.494 - -0.337
# -0.337 - -0.198
# -0.198 - -0.064
# -0.064 - 0.033
# 0.033 - 0.092
# 0.092 - 0.14
# 0.14 - 0.194
# 0.194 - 0.324
# 0.324 - 0.528
# 0.528 - 0.901
Figure - 15: V-component of velocity for 2002 Kultali cyclone

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4.36
INDIA
BANGLADESH
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MYANMAR
Cyclone Track
Figure - 16: Track and computed surge for 1981 Namkhana Cyclone

4.37
U-Component of Velocity (Surface currents)
INDIA
BANGLADESH
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Country.shp
Sort-uc1.txt
# -0.349 - -0.21
# -0.21 - -0.141
# -0.141 - -0.116
# -0.116 - -0.09
# -0.09 - -0.065
# -0.065 - -0.04
# -0.04 - -0.012
# -0.012 - 0.026
# 0.026 - 0.105
# 0.105 - 0.31
Figure - 17: U-component of velocity for 1981 Namkhana cyclone

4.38
V-Component of velocity (Surface currents)
INDIA
BANGLADESH
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Country.shp
Sort-vc1.txt
# -0.505 - -0.29
# -0.29 - -0.209
# -0.209 - -0.151
# -0.151 - -0.102
# -0.102 - -0.062
# -0.062 - -0.021
# -0.021 - 0.025
# 0.025 - 0.078
# 0.078 - 0.15
# 0.15 - 0.31
Figure - 18: V-component of velocity for 1981 Namkhana cyclone

Chapter Five
Vulnerability Assessment for Coastal Districts of
West Bengal
5.1. Vulnerability Assessment
In the last five decades, it has been observed that there was an exponential rise in human and
material losses from disaster events. Albeit there is no clear evidence that the frequency or intensity
of disastrous events has increased. This clearly points out that the rise in disaster related
consequences was related to the vulnerability of the people that has been induced by the human
determined path of development.
Whatever may be the disasters origin, its consequences will not only depend on the hazard’s intrinsic
severity and intensity, but also on the people’s vulnerability and socio-economic resistance to violent
and unexpected occurrences. Put into simple words, even which drive the disaster may have an
origin beyond the limits of man; its ultimate effect upon the state of welfare will generally depend on
man-made physical economic and social infrastructure.
A proper understanding of the factors which determines a disaster’s effect, in terms of people’s
welfare, is then important both in identifying and evaluating prevention measures aimed at reducing
people’s vulnerability, after each disaster, the type and amount of damage experienced by affected
population.
It has also been observed that in every disaster, it is the communities that are on the receiving end,
and those who are the first casualties and are hardest hit - are the poor. Prime reason is that, more
and more people in lower socio-economic stratum tend to inhabit in marginal and exposed land. It is
poverty which drives this underprivileged people to live in precarious locations and adopt
unsustainable means of survival – making them increasingly more vulnerable to the natural and man
made disasters.
Disaster management plans prepared on the feed back of the vulnerability studies, instead of only
concentrating on the hazard assessment studies, will perhaps better address the issues of social
equity and justice.
This component of the study will focus on the inherent characteristics of the human settlements
which make it vulnerable to the tropical cyclones and related risks. Assessing the vulnerability of the
CHAPTER 5

5.2
particular human settlement to a particular hazard should address its level of vulnerability with
respect to each of the following aspect:
a) Housing Stock
b) Local economy
c) Physical and Social Infrastructure
d) Incidence of loss on various socio-economic groups
e) Human Mortality and Morbidity
The ‘Degree of Vulnerability’ of any system or its components can only be assessed through
contemplating its performance under hypothetical hazard scenario with varying intensity. The study
area lies within the Very High Damage Risk Zone delineated by the Vulnerability Atlas prepared by
BMTPC, indicating that Average Recurrence Interval (ARI) of 50 years for wind gusts having speed
more than 198 kmph (at the height of 10 m from the surface for more than 3 seconds). It also
indicates same ARI for storm surge height coupled with tidal fluctuation of 12.5 m height on the South
24-parganas coast and 12.0 m height on the East Midnapore coast. For the vulnerability assessment
this hypothetical hazard scenario has been adopted, however, in some blocks, the level of hazard is
expected to be far worse than this assumed intensity and periodicity.
In the following sections, each aspect of vulnerability will be discussed along with comparative
assessment at CD block level for the coastal districts of West Bengal.
5.2. Assessment of Housing Stock
Damage done to the human shelter is one of the most significant consequences of tropical cyclone.
The wind pressures and suction effect on housing structures due to high velocity of wind can be
sufficient to lift them off and fly away – known as aerofoil effects. The main destruction due to high
wind velocities occurs in the traditional non-engineered buildings using local clay, adobe or agrobased
materials. The engineered buildings also suffer huge damage unless appropriate precautions
are taken into consideration during building construction. Apart from these, substantial non-structural
damage occurs to doors and windows, cladding, wall panels etc in heavy engineered construct due
to wind gust.
On the other hand, tropical cyclones are always accompanied with heavy precipitation resulting in
huge surface run-off from the catchment basin to the drainage channels. Combined with the storm
surge these results in inundation and flooding. Damage to the housing stock depends on the water

5.3
level and the period of inundation. Houses with low plinth heights and temporary wall materials are
subjected to significant damage. However, it should be noted that damage due to inundation also
depends on whether tropical cyclone has taken place pre-monsoon or post monsoon.
The values of the Vulnerability Index (A) for Housing Stock from Cyclonic effects has been calculated
by taking into account the share of houses having temporary roof material. Similarly, values of the
Vulnerability Index (B) for Housing Stock from Inundation have been calculated by taking into
account the share of houses having temporary wall material. Both indexes has been normalized for
better interpretation in the way mentioned following.
No.
of houses with temporary roof material in ith CD block
Ai
=
Total no.
of houses in ith CD block
Aˆ
=
i
H
i
Ai
− A
A − A
max
min
Bi
B
Bˆ
−
i
=
B − B
min
No.
of houses with temporary wall material in ith CD block
Bi
=
Total no.
of houses in ith CD block
max
min
min
⎛ Aˆ
i
Bˆ
⎞
⎜
+
i
= ⎟
+
2
⎝ ⎠
( Aˆ
. Bˆ
)
i
i
Figure 5-1: Vulnerability mapping of the housing stock in the coastal districts of West Bengal

5.4
The Composite Vulnerability Index (H) of the Housing Stock in a particular CD Block has been
calculated taking into account the vulnerability indexes for both cyclonic effects and inundation
effects [Refer Table 5-1 and Figure 5-1]. The functional form specified for aggregation has tried to
capture both the additive effects as well as multiplicative effects of individual vulnerability indexes. It
is tautological to mention that, a particular community vulnerable with respect to parameter A as well
as B is more vulnerable compared to combined vulnerability of communities only vulnerable to
parameter A or B. For example, degree of disability of a person who has lost his arm and leg both is
more than added disability of one who has lost only his arm and one who has lost his leg.
Table 5-1: Composite Vulnerability Index of Housing Stock in the coastal districts of West Bengal
Sub-Div.
C.D Block
Total no.
of Houses
Share of
houses with
Temporary Roof
Material
( Â i
)
Share of houses
with
Temporary Wall
Material
( ) i
Bˆ ( L )
i
Alipore Sub Division
Thakurpukur-
Maheshtala 34,835 0.724 0.522 0.968 0.955 1.237
Bishnupur-I 51,792 0.863 0.792 0.982 0.976 1.656
Bishnupur-II 47,584 0.771 0.613 0.978 0.970 1.385
Budge-Budge(Part-I) 24,246 0.833 0.733 0.980 0.972 1.565
Budge-Budge(Part-II) 43,296 0.827 0.720 0.979 0.971 1.545
Baruipur
Sub Division
Sonarpur 39,655 0.853 0.771 0.957 0.939 1.578
Joynagar-I 51,355 0.850 0.765 0.989 0.987 1.631
Joynagar-II 44,641 0.925 0.910 0.984 0.978 1.835
Kultali 41,854 0.971 1.000 0.996 0.998 1.997
Baruipur 82,631 0.828 0.722 0.974 0.964 1.540
Bhangore-I 44,970 0.875 0.814 0.977 0.969 1.680
Bhangore-II 44,737 0.851 0.768 0.989 0.987 1.635
Canning
Sub Division
Canning-I 58,500 0.927 0.915 0.985 0.981 1.846
Canning-II 39,635 0.959 0.978 0.996 0.998 1.963
Basanti 66,862 0.963 0.985 0.991 0.990 1.963
Gosaba 60,625 0.964 0.986 0.997 0.998 1.977
Diamond Harbour
Sub Division
Mograhat-I 49,172 0.857 0.779 0.985 0.980 1.643
Mograhat-II 55,380 0.862 0.788 0.986 0.982 1.659
Mandirbazar 41,037 0.886 0.835 0.988 0.985 1.732
Kulpi 56,138 0.926 0.913 0.993 0.994 1.860
Falta 53,697 0.832 0.730 0.989 0.987 1.580
D-Harbour-I 29,627 0.865 0.795 0.997 0.999 1.691
D-Harbour-II 38,475 0.837 0.741 0.990 0.989 1.598
Mathurapur-I 36,672 0.922 0.905 0.994 0.995 1.851
Mathurapur-II 45,533 0.937 0.934 0.996 0.997 1.897
Kakdwip
Sub
Division
Kakdwip 55,156 0.907 0.876 0.992 0.992 1.802
Namkhana 41,456 0.948 0.956 0.995 0.996 1.929
Sagar 46,179 0.964 0.987 0.997 0.999 1.979

5.5
Patharprotima 70,576 0.967 0.993 0.998 1.000 1.989
Tamluk
Sub Division
Tamluk 50,690 0.848 0.762 0.524 0.277 0.731
Sahid Matangini 40,997 0.861 0.786 0.546 0.312 0.794
Panskura-I 76,071 0.863 0.791 0.666 0.494 1.033
Panskura-II 64,697 0.784 0.638 0.540 0.302 0.663
Moyna 49,786 0.942 0.943 0.688 0.528 1.233
Nandakumar 55,689 0.919 0.900 0.580 0.363 0.958
Nandigram-III 39,032 0.936 0.933 0.748 0.620 1.355
Haldia
Sub Division
Mahisadal 41,740 0.868 0.800 0.556 0.327 0.825
Nandigram-I 40,304 0.943 0.947 0.826 0.738 1.542
Nandigram-II 26,249 0.960 0.979 0.822 0.733 1.573
Sutahata 48,895 0.455 0.000 0.342 0.000 0.000
Egra
Sub Division
Patashpur-I 34,921 0.961 0.981 0.920 0.882 1.798
Patashpur-II 35,146 0.960 0.979 0.907 0.862 1.763
Bhagwanpur-I 44,138 0.952 0.962 0.821 0.730 1.549
Egra-I 32,658 0.950 0.959 0.908 0.864 1.739
Egra-II 34,491 0.928 0.916 0.830 0.745 1.513
Contai
Sub Division
Khejuri -I 27,469 0.942 0.945 0.837 0.755 1.563
Khejuri-II 27,597 0.961 0.982 0.884 0.827 1.715
Bhagwanpur-II 40,075 0.953 0.966 0.837 0.755 1.590
Ramnagar-I 35,090 0.810 0.687 0.661 0.487 0.921
Ramnagar-II 35,480 0.903 0.868 0.763 0.642 1.312
Contai-I 36,112 0.895 0.853 0.751 0.624 1.272
Contai-II 34,024 0.913 0.888 0.795 0.691 1.403
Contai-III 33,474 0.925 0.910 0.834 0.751 1.514
5.3. Vulnerability Assessment of Local economy
A brief look at the local economy of the study area clearly indicates its agrarian nature. More than 48
percent of the work force is engaged in primary sector activities, whereas 44 percent of the work
force is absorbed in the service sector. Merely 6 percent of labor force in employed in manufacturing
and processing activities. Preliminary investigation of the service employment reveals that most of
them are in informal sector – a component which belongs to the marginal worker class.
Looking at the low volume of industrial activity, the vulnerability assessment of the local economy has
primarily concentrated on three aspects – agriculture, pisciculture and livestock. The prime reasoning
being that most of the small and medium scale manufacturing activities are located in the urban
areas and are comparatively better insulated from the vagaries of nature. On the other hand, informal
service economy is primarily driven by human capital with low physical capital inputs.
The Vulnerability Index of the Agriculture (A) has been estimated based on the total value of the
standing crops and the opportunity cost due to lost productivity in coming years at the market prices

5.6
(2004 prices) prevalent in district mandis. Intrusion of salinity in soil reduces the productivity of the
land, inflicting significant opportunity costs as well as restoration costs on the cultivator.
Given its role in income and employment in the study area, the Vulnerability Index of Pisciculture (B)
has also been estimated from the total fish production and prevailing local market prices.
It should be noted that intrusion of salinity from storm surge related inundation diminishes the yield of
the fish production, both for sweet and brackish water pisciculture.
Similarly, the Vulnerability Index of the Livestock and Animal Husbandry (C) has been estimated by
their market value prevalent in the local markets.
A = Total value of annual agricultural output ( INR)
in ith CD block
i
B = Total value of fish output ( INR)
in ith CD block
i
C = Total value of livestock ( INR)
in ith CD block
i
All the three indexes have been normalized in the following way, for better inter CD block wise
comparison of vulnerability, in parts and also in entirety.
Aˆ
=
i
Ai
− A
A − A
max
min
min
Bˆ
i
=
Bi
B
max
− B
− B
min
min
Cˆ
i
Ci
=
C
max
− C
− C
min
min
Figure 5-2: Vulnerability mapping of the local economy in the coastal districts of West Bengal

5.7
The Composite Vulnerability Index for the Local Economy (E) has been assessed by considering
the vulnerability indexes of agriculture, pisciculture and livestock [Refer Table 5-2 and Figure 5-2].
The functional form specified for aggregation is similar to the one used for estimating Composite
Index of Vulnerability for Housing Stock [Refer Section 5.2.]
⎛ Aˆ
i
Bˆ
i
Cˆ
⎞
i
E ⎜
+ +
⎟
i
=
+
3
⎝ ⎠
( Aˆ
. Bˆ
Cˆ
)
i
i
i
Table 5-2: Composite Vulnerability Index of Local economy in the coastal districts of West Bengal
Sub-
C.D Block
Div.
( Â i
)
( Bˆ i
)
( Ĉ i
)
( E i
)
Thakurpukur-
Maheshtala 0.0000 0.0002 0.383053 0.128
Bishnupur-I 0.0305 0.0198 0.082344 0.044
Alipore
Sub Division
Bishnupur-II 0.2251 0.2054 0.337292 0.272
Budge-
Budge(Part-I) 0.0020 0.0000 0.173545 0.059
Budge-
Budge(Part-II) 0.0149 0.1966 0.237498 0.150
Baruipur
Sub Division
Sonarpur 0.0114 0.2488 0.442839 0.236
Joynagar-I 0.0143 0.2152 0.323337 0.185
Joynagar-II 0.2533 0.2570 0.237226 0.265
Kultali 0.0420 0.5941 0.468972 0.380
Baruipur 0.0502 0.2059 0.547945 0.274
Bhangore-I 0.3063 0.1313 0.273773 0.248
Bhangore-II 0.2433 0.4236 0.495718 0.439
Canning
Sub Division
Canning-I 0.0260 0.9347 0.375476 0.455
Canning-II 0.0815 1.0000 0.339351 0.501
Basanti 0.2656 0.3538 0.901268 0.592
Gosaba 0.2765 0.5739 0.907687 0.730
Diamond Harbour
Sub Division
Mograhat-I 0.0398 0.1594 0 0.066
Mograhat-II 0.0378 0.1922 0.214468 0.150
Mandirbazar 0.0201 0.0366 0.269151 0.109
Kulpi 0.0342 0.3466 0.430276 0.275
Falta 0.0459 0.0890 0.296854 0.145
D-Harbour-I 0.0155 0.3700 0.137256 0.175
D-Harbour-II 0.0206 0.1274 0.210887 0.120
Mathurapur-I 0.0054 0.1054 0.192789 0.101
Mathurapur-II 0.0358 0.4105 0.458835 0.308
Kakdwip
Sub Division
Kakdwip 0.0425 0.4808 0.691852 0.419
Namkhana 0.0376 0.5106 0.699353 0.429
Sagar 0.0458 0.5585 0.756069 0.473
Patharprotima 0.0833 0.9086 0.947036 0.718
Tamluk
Sub Division
Tamluk 0.4139 0.0761 0.349495 0.291
Sahid Matangini 0.2647 0.0213 0.293726 0.195
Panskura-I 0.9297 0.0875 1 0.754
Panskura-II 0.4790 0.0846 0.476509 0.366

5.8
Moyna 0.6280 0.1592 0.542286 0.497
Nandakumar 0.5394 0.0706 0.567176 0.414
Nandigram-III 0.2716 0.1707 0.347487 0.279
Haldia
Sub Division
Mahisadal 0.5332 0.0950 0.451286 0.383
Nandigram-I 0.2924 0.1481 0.413053 0.302
Nandigram-II 0.2317 0.0604 0.336969 0.214
Sutahata 0.1309 0.0423 0.23964 0.139
Egra
Sub Division
Patashpur-I 0.8649 0.2675 0.612328 0.723
Patashpur-II 1.0000 0.0832 0.572259 0.599
Bhagwanpur-I 0.4896 0.1376 0.50763 0.413
Egra-I 0.5338 0.0848 0.606545 0.436
Egra-II 0.5077 0.1440 0.564641 0.447
Contai
Sub Division
Khejuri -I 0.2585 0.0730 0.331388 0.227
Khejuri-II 0.1854 0.0780 0.377971 0.219
Bhagwanpur-II 0.4078 0.1121 0.561826 0.386
Ramnagar-I 0.2215 0.0291 0.327166 0.195
Ramnagar-II 0.4324 0.0641 0.357101 0.294
Contai-I 0.2065 0.1223 0.402414 0.254
Contai-II 0.2729 0.0534 0.429623 0.258
Contai-III 0.1842 0.0755 0.644642 0.310
5.4. Vulnerability Assessment of Physical and Social Infrastructure
Impact of a disaster can be appropriately evaluated by the time needed to restore normalcy. And
disaster of any kind invariably tends to curtail the man’s ability to restore normalcy by severely
affecting its physical and social infrastructure. In this study we will primarily concentrate on threes
basic types of physical infrastructure, namely a) road connectivity, b) access to safe drinking water
and c) access to hygienic sanitation facilities. Apart from that, we will also focus on a) education and
b) heath infrastructure and their role in dictating the vulnerability of a particular settlement.
5.4.1. Physical infrastructure
Road connectivity is of paramount importance as it guides the success of evacuation during pre and
post disaster stages as well as reaching of aid and relief to the affected population. Road connectivity
index of a particular CD block has been derived from road length in km per sq.km area as well as per
‘000 population. Both surfaced as well as unsurfaced roads have been taken into consideration along
with relative share. Higher the road connectivity lesser it is vulnerable to impediments in the
evacuation as well as aid and relief distribution. Disruption in the road connectivity can be either due
to temporary blockages due uprooted trees or due to damage of the culverts and bridges. Based on

5.9
the time required to restore the road connectivity, the mobility in the primary (within CD block),
secondary (district level) and tertiary catchment (intra region) area will be affected.
The index of road connectivity (A) along with its normalized value has been calculated as shown
following.
⎛ X
Ai
=
⎜
⎝ Yi
where,
X
Y = Total area in sq.
kms in ith CD block
i
Z
i
i
i
Aˆ
=
i
⎞ ⎛ X ⎞
i
⎟.
⎜
Z
⎟
⎠ ⎝ i ⎠
= Total length of roads in kms in ith CD block
= Total population in '000 persons in ith CD block
A
A
max
max
− Ai
− A
min
Access to safe drinking water source is one of the most crucial parameters which dictate the
incidence of epidemics especially from water borne diseases in the aftermath of flood. Tropical
cyclones, often leading to inundation and flooding contaminate the sources of the drinking water
creating pathogenic condition and increasing the chances of mortality and morbidity in child and aged
section of the population. Similarly, sources of defecation will guide the extent of contamination of the
local water sources as well as the level of environmental degradation after the flooding. The
vulnerability of water supply and sanitation facilities are estimated based on the percentage share of
the households having access to sources of water with low chances of contamination (Tap and Tube
well) as well as access to hygienic defecation facilities (Pit latrine and Water closet).
⎛ X
i
⎞
Bi
=
⎜
Z
⎟.100
⎝ i ⎠
⎛ Yi
⎞
Ci
=
⎜ .100
Z
⎟
⎝ i ⎠
where,
X
= Total no.
of HH having access to safe drinking water in i th CD block
Yi
= Total no.
of HH having access to safe sanitation facility in i th CD block
Z = Total no.
of HH in i th CD block
i
i
Bˆ
i
=
B
B
max
max
− Bi
− B
min
ˆ C
Ci
=
C
max
max
− Ci
− C
min

5.10
5.4.2. Social infrastructure
Health and education facilities are the most important social infrastructure towards minimizing the
indirect damage, beginning almost after the incidence of disaster and possibly extending into the
rehabilitation period.
Vulnerability of the health infrastructure is assessed at the CD block level by the degree of access its
settlements has with respect to health care facilities (Primary Health Care center, Sub center, Health
center or Hospital facilities). Higher the level of access, lesser is impediment in reducing the burden
of disease after the disaster has taken place. Past records clearly show that diarrhoeal diseases
claim too many precious human lives (mostly children from age group 0-10 and the aged population
i.e. 60 + age group), which can be significantly reduced by preventive health care measures – and
communities with poor health facilities just cannot do that.
Existing educational facilities, apart from providing education, actively take part in imparting mass
literacy and community awareness programs. Communities with better level of education
infrastructure have greater probability of minimizing the impact of tropical cyclones due to increased
awareness and community level initiatives. Moreover, communities with better educational facilities
will have minimum disruption in education due to faster restoration of normalcy.
Level of access to education facilities (primary school, intermediate school, secondary school and
other higher educational institutions) will guide the vulnerability of the education infrastructure.
⎛ X ⎞
i
Di
=
⎜
Z
⎟
⎝ i ⎠
⎛ Y ⎞
i
Ei
=
⎜
Z
⎟
⎝ i ⎠
where,
X = Total no.
of health care facilities in i th CD block
Y = Total no.
of education facilities in i th CD block
i
Z = Total no.
of inhabited villages in i th CD block
i
i
Dˆ
i
=
D
D
max
max
− Di
− D
min
ˆ E
Ei
=
E
max
max
− Ei
− E
min

5.11
Figure 5-2: Vulnerability mapping of the infrastructure in the coastal districts of West Bengal
Composite Index of Vulnerability for Infrastructure (I) has also been estimated by taking
individual indexes into consideration for both physical and social infrastructure [Refer Table 5-3 and
Figure 5-3]. The functional form specified for aggregation is similar to the one used for estimating
Composite Index of Vulnerability for Housing Stock [Refer Section 5.2.]
( Aˆ
. Bˆ
. Cˆ
. Dˆ
. Eˆ
)
⎛ Aˆ
Bˆ
Cˆ
Dˆ
Eˆ
⎞
I ⎜
i
+
i
+
i
+
i
+
i
i
=
⎟
i i i i i
5
+
⎝
⎠
where,
Aˆ
= Normalised Vu ln erability Index of Road connectivity in i th CD block
i
Bˆ
= Normalised Vu ln erability Index of Drinking water source in i th CD block
i
Cˆ
= Normalised Vu ln erability Index of Sanitation facility in i th CD block
i
Dˆ
= Normalised Vu ln erability Index of Health inf rastructure in i th CD block
i
Eˆ
= Normalised Vu ln erability Index of Education Infrastructure in i th CD block
i
Table 5-3: Composite Vulnerability Index of Infrastructure in the coastal districts of West Bengal
Sub-Div. C.D Block ( Â ) i
( Bˆ i
) ( Ĉ i
) ( Dˆ i
) ( i
)
Alipore
Sub Division
Ê ( I )
i
Thakurpukur-
Maheshtala 0.8850 0.704 0.062 0.529 0.714 0.418
Bishnupur-I 0.7689 0.668 0.463 0.583 0.769 0.635
Bishnupur-II 0.6779 0.634 0.458 0.947 0.664 0.724
Budge-Budge(Part-I) 0.2707 0.950 0.469 0.504 0.280 0.503

5.12
Budge-Budge(Part-II) 0.0000 0.659 0.580 0.504 0.715 0.629
Baruipur
Sub Division
Sonarpur 1.0000 0.846 0.148 0.615 0.987 0.595
Joynagar-I 0.6717 0.520 0.536 0.372 0.958 0.577
Joynagar-II 0.9191 0.928 0.034 0.320 0.944 0.455
Kultali 0.9646 0.846 0.821 0.062 0.969 0.581
Baruipur 0.9923 0.748 0.266 0.719 0.988 0.686
Bhangore-I 0.9885 0.880 0.549 0.909 1.000 1.107
Bhangore-II 0.9440 0.918 0.483 0.833 0.985 1.007
Canning
Sub Division
Canning-I 0.9392 0.838 0.510 0.947 0.655 0.855
Canning-II 0.9990 0.962 0.701 0.536 0.765 0.870
Basanti 0.9887 0.800 0.817 0.636 0.580 0.808
Gosaba 0.9868 0.824 0.731 0.336 0.357 0.521
Diamond Harbour
Sub Division
Mograhat-I 0.7472 0.809 0.988 0.713 0.755 1.083
Mograhat-II 0.9389 0.916 0.547 0.931 0.697 0.943
Mandirbazar 0.9212 1.000 1.000 0.833 0.785 1.377
Kulpi 0.9946 0.977 0.800 0.778 0.791 1.150
Falta 0.9332 0.281 0.499 0.887 0.799 0.593
D-Harbour-I 0.8148 0.554 0.584 0.624 0.794 0.672
D-Harbour-II 0.9331 0.791 0.451 0.559 0.751 0.660
Mathurapur-I 0.6421 0.912 0.752 0.784 0.759 1.049
Mathurapur-II 0.9568 0.749 0.737 0.037 0.000 0.305
Kakdwip
Sub Division
Kakdwip 0.8611 0.556 0.662 0.570 0.201 0.440
Namkhana 0.9689 0.000 0.836 0.599 0.484 0.384
Sagar 0.9004 0.205 0.799 0.685 0.346 0.446
Patharprotima 0.8969 0.863 0.908 0.000 0.507 0.455
Tamluk
Sub Division
Tamluk 0.9463 0.647 0.660 0.681 0.798 0.790
Sahid Matangini 0.9393 0.809 0.478 0.753 0.799 0.801
Panskura-I 0.9156 0.610 0.663 0.953 0.938 0.994
Panskura-II 0.9579 0.834 0.502 0.645 0.788 0.766
Moyna 0.9874 0.653 0.744 0.652 0.722 0.783
Nandakumar 0.9292 0.637 0.448 0.640 0.749 0.632
Nandigram-III 0.9299 0.850 0.734 0.722 0.851 1.014
Haldia
Sub Division
Mahisadal 0.8343 0.624 0.612 0.780 0.731 0.767
Nandigram-I 0.9732 0.907 0.445 0.845 0.821 0.883
Nandigram-II 0.6394 0.959 0.000 0.384 0.633 0.395
Sutahata 0.9522 0.777 0.555 0.688 0.863 0.833
Egra
Sub Division
Patashpur-I 0.8638 0.994 0.494 0.916 0.829 1.020
Patashpur-II 0.9932 0.953 0.842 0.972 0.934 1.469
Bhagwanpur-I 0.9120 0.757 0.228 0.815 0.869 0.656
Egra-I 0.9232 0.926 0.514 1.000 0.887 1.087
Egra-II 0.8874 0.783 0.690 0.711 0.867 0.943
Contai
Sub
Division
Khejuri -I 0.8306 0.894 0.520 0.875 0.584 0.812
Khejuri-II 0.9315 0.696 0.842 0.885 0.887 1.122
Bhagwanpur-II 0.8337 0.676 0.571 0.902 0.877 0.910

5.13
Ramnagar-I 0.9920 0.697 0.744 0.922 0.880 1.069
Ramnagar-II 0.9306 0.790 0.217 0.817 0.909 0.674
Contai-I 0.9753 0.710 0.191 0.908 0.930 0.662
Contai-II 0.9496 0.830 0.508 0.852 0.914 0.949
Contai-III 0.1820 0.619 0.296 0.921 0.898 0.699
5.5. Incidence of loss on various socio-economic groups
Magnitude of loss due to natural disasters is important, but it is also important to analyze the
incidence of loss on various socio-economic groups. A brief look at the socio-economic
characteristics indicate that some of the areas are one the most impoverished and backward region
in the state. And therefore the true vulnerability of human welfare from tropical cyclones can only be
assessed with due attention to socio-economic inequalities persistent spatially across the study area.
Moreover, the study area is endowed with vast reserve of ecologically sensitive mangrove forests. It
has been observed that livelihood of socio-economically weaker groups are dependent on these
forests. And in distress, this dependence rises significantly leading to rapid deterioration of the
environmental assets.
Among diverse range of indicators, eight indicators have been chosen to represent various aspects
of socio-economic vulnerability among the CD blocks. The indicators are mentioned following:
1. Share of workforce engaged in primary sector activities
2. Share of SC/ST population
3. Access to banking services
4. Net savings
5. Access to household electricity connection
6. Type of cooking fuel used
7. Female literacy
8. Access to Radio
In the following sections, the significance and role of each indicator are elaborated along with the
methodology for quantification.
5.5.1. Share of workforce engaged in primary sector activities
In the previous sections, it has been mentioned that primary sector activities are the principle sources
of income and employment in the study area. It has also been found the primary sector activities,
particularly agriculture, pisciculture and animal husbandry, are more vulnerable compared to

5.14
secondary and tertiary activities. Therefore, the impact of tropical cyclone will be more pronounced
on the people depending for livelihood on primary sector activities compared to others. Degree of
vulnerability (A) will vary across the CD blocks with varying share of primary sector workforce. Higher
the share of workforce involvement in these activities, greater the incidence of economic distress due
to cyclones and consequential flooding.
⎛Workforce
engaged in primary sector
activities in ith CD block ⎞
Ai
= ⎜
⎟.100
⎝
Total workforce in ith CD block
⎠
ˆ Ai
− Amin
Ai
=
A − A
max
min
5.5.2. Share of SC/ST population
There is no denial of the fact that SC/ST population are one the most disadvantaged sections of the
community and any loss due to natural disasters incident on them will viciously affect their level of
welfare. Besides that, restoration of normalcy for these socio-economic groups is severely limited
due to lower endowment of resources. As significant percentage of SC/ST population inhabit in some
parts of the study area, it is imperative to include this parameter in the socio-economic vulnerability
assessment framework.
⎛ Total population of backward classes in ith CD block ⎞
Bi
= ⎜
⎟
⎝ Total population in ith CD block ⎠
ˆ Bi
− Bmin
Bi
=
B − B
max
min
5.5.3. Access to banking services
In developed sections of the society, the elements which are at risk (physical assets) from natural
disaster consists a small part of the total asset, as the bulk component is protected and insured by
banks and other financial institutions. However, this trend gets reversed in case of poorer sections of
community. Number of households accessing banking facilities acts as a decent proxy to appraise
the share of total household assets exposed to risk events.
Higher the number of households availing banking services in a particular CD block, lesser will be the
incidence of misery due cyclones and consequential flooding.

5.15
C
i
Cˆ
i
⎛ Total no.
of
= ⎜
⎝
Cmax
− Ci
=
C − C
max
min
households availing banking services in ith CD block
Total no.
of households in ith CD block
⎞
⎟
⎠
5.5.4. Net savings
Net savings per household particularly in the small saving scheme gives important insight into the
capability of restoration after the extreme event has taken place. It also reflects the material
prosperity of the households as savings is directly proportional to the income, assuming that vast
change in consumption pattern will not be exhibited across the study area.
D = Savings per household in ith CD block
i
Dˆ
i
D
=
D
max
max
− Di
− D
min
5.5.5. Access to household electricity connection
One of the frequently used indicator as proxy to level of material welfare of households is its access
to electricity, primarily for the purpose of illumination. Communities with higher level of material
welfare is expected to perform better in case of extreme hazardous events – as they have greater
resources to restore normalcy back. Number of households having electrical connection at household
level has been taken as an indicator of socio-economic vulnerability.
⎛ Total no.
of
Ei
= ⎜
⎝
ˆ Emax
− Ei
Ei
=
E − E
max
min
households with access to electricity in ith CD block
Total no.
of households in ith CD block
⎞
⎟
⎠
5.5.6. Type of cooking fuel used
Type of the cooking fuel used directly indicates the level of affluence of the particular household.
More importantly it explores the dependence of household activities on the adjoining forest reserves.
Frequently issues have been raised regarding the exploitation of the forests for fire wood collection.
After the extreme events, the dependence on forests rises for the communities adjoining them
leading to rapid deterioration of natural environment – which can have significant repercussions in
the long term. Number of households having access to proper cooking fuel (LPG, Biogas, coal and
kerosene) has been used as an indicator of socio-economic vulnerability.

5.16
F
i
Fˆ
i
⎛ Total no.
of
= ⎜
⎝
Fmax
− Fi
=
F − F
max
min
households u sin g proper cooking fuel in ith CD block
Total no.
of households in ith CD block
⎞
⎟
⎠
5.5.7. Female literacy
Awareness of the community plays an important role in reducing the impact of disasters by taking
preventive measures and mitigating the consequences after the event has happened. Cost of
prevention is far lesser than the value of the loss in its absence and there is universal mandate to
upgrade the capability of communities to take up these measures. On the other hand, the indirect
damage especially mortality and morbidity due to pathogenic environment developed aftermath of an
extreme event can be greatly reduced by adopting simple preventive health measures.
It is universally acclaimed fact that awareness quotient of any community cannot better be
represented by the female literacy. CD block wise comparison of female literacy will help assess the
level of awareness and pro-activeness.
⎛ Total literate
Gi
=
⎜
⎝ Total
ˆ Gmax
− Gi
Gi
=
G − G
max
min
female population in ith CD block ⎞
.100
population in ith CD block
⎟
⎠
5.5.8. Access to Radio
Dissemination of warning can play a deciding role in minimizing the loss of human lives as well as
physical assets. Radio and television are the most pervasive instruments to achieve this end.
Important messages concerned with relief and rehabilitation can also be broadcasted through them –
reducing the misery of the affected people. However, given the price and mobility aspect of the
equipment, number of households having possession of radio has been used as an indicator for
assessing this aspect of socioeconomic vulnerability.
⎛ Total no.
of households in possession of radio in ith CD block ⎞
Hi
=
⎜
Total no.
of households in ith CD block
⎟
⎝
⎠
ˆ H
max
− Hi
Hi
=
H − H
max
min

5.17
Figure 5-3: Mapping of the socio-economic vulnerability in the coastal districts of West Bengal
Composite Index of Socio-economic Vulnerability (S) has also been estimated by taking
individual vulnerability indexes into consideration all the attributes discussed above [Refer Table 5-4
and Figure 5-4].
The functional form specified for aggregation is similar to the one used for estimating Composite
Index of Vulnerability for Housing Stock [Refer Section 5.2.]
⎛ Aˆ
i
+ Bˆ
i
+ Cˆ
i
+ Dˆ
i
+ Eˆ
i
+ Fˆ
i
+ Gˆ
i
+ Hˆ
Si
= ⎜
⎝
8
where,
Aˆ
i
= Index of
Bˆ
i
= Index of
Cˆ
i
= Index of
Dˆ
i
= Index of
Eˆ
i
= Index of
Fˆ
i
= Index of
Gˆ
i
= Index of
Hˆ
= Index of
i
i
⎞
⎟ +
⎠
( Aˆ
. Bˆ
. Cˆ
. Dˆ
. Eˆ
. Fˆ
. Gˆ
. Hˆ
)
share of workforce in Pr imary sector
activities in i th CD block
share of Backward population in i th CD block
share of households availing Banking facility in i th CD block
Savings per household in i th CD block
share of households having Electrical connection in i th CD block
share of households having proper Cooking fuel in i th CD block
percentage of Female literacy in i th CD block
share of households in possesion of Radio in i th CD block
i
i
i
i
i
i
i
i

5.18
Table 5-4: Composite Index of Socio-economic Vulnerability in the coastal districts of West Bengal
Sub-
Div.
C.D Block ( Â i
) ( Bˆ i
) ( Ĉ i
) ( Dˆ i
) ( Ê i
) ( Fˆ i
) ( Ĝ i
) ( i
)
Ĥ ( S )
i
Alipore
Sub Division
Thakurpukur-
Maheshtala 0.023 0.482 0.485 0.650 0.185 0.115 0.239 0.527 0.338
Bishnupur-I 0.188 0.618 0.975 0.813 0.480 0.688 0.425 0.768 0.629
Bishnupur-II 0.127 0.141 1.000 0.819 0.368 0.614 0.313 0.711 0.512
Budge-
Budge(Part-I) 0.000 0.214 0.870 0.650 0.536 0.603 0.276 0.690 0.480
Budge-
Budge(Part-II) 0.165 0.212 0.973 0.969 0.388 0.751 0.328 0.757 0.570
Baruipur
Sub Division
Sonarpur 0.154 0.792 0.451 0.000 0.474 0.522 0.410 0.474 0.410
Joynagar-I 0.197 0.515 0.472 0.788 0.739 0.736 0.624 0.714 0.607
Joynagar-II 0.336 0.458 0.796 0.926 0.915 0.956 0.858 0.768 0.817
Kultali 0.486 0.647 0.902 0.878 1.000 1.000 0.880 0.533 0.908
Baruipur 0.317 0.545 0.000 0.398 0.000 0.000 0.464 0.618 0.293
Bhangore-I 0.273 0.265 0.717 0.955 0.693 0.892 0.698 0.698 0.664
Bhangore-II 0.326 0.249 0.748 0.971 0.783 0.941 0.504 0.824 0.686
Canning
Sub Division
Canning-I 0.440 0.678 0.637 0.997 0.730 0.429 0.789 0.772 0.720
Canning-II 0.561 0.359 0.878 0.998 0.958 0.979 1.000 1.000 1.007
Basanti 0.615 0.573 0.724 0.995 0.993 0.977 0.889 0.622 0.934
Gosaba 0.484 1.000 0.676 1.000 0.985 0.987 0.538 0.187 0.764
Diamond Harbour
Sub Division
Mograhat-I 0.195 0.229 0.602 0.997 0.755 0.929 0.541 0.742 0.631
Mograhat-II 0.219 0.443 0.434 0.959 0.686 0.887 0.561 0.858 0.643
Mandirbazar 0.123 0.553 0.704 0.922 0.782 0.898 0.632 0.798 0.692
Kulpi 0.236 0.380 0.570 0.961 0.792 0.897 0.567 0.692 0.651
Falta 0.241 0.273 0.495 0.774 0.471 0.844 0.387 0.778 0.536
D-Harbour-I 0.197 0.207 0.777 0.448 0.763 0.896 0.530 0.972 0.604
D-Harbour-II 0.167 0.309 0.669 0.867 0.690 0.838 0.399 0.710 0.586
Mathurapur-I 0.168 0.461 0.793 0.978 0.858 0.954 0.655 0.902 0.750
Mathurapur-II 0.448 0.370 0.749 0.999 0.913 0.971 0.587 0.477 0.720
Kakdwip
Sub Division
Kakdwip 0.716 0.452 0.622 0.987 0.765 0.819 0.467 0.388 0.675
Namkhana 0.532 0.298 0.739 0.986 0.931 0.978 0.225 0.000 0.586
Sagar 0.690 0.324 0.712 0.990 0.985 0.990 0.239 0.015 0.619
Patharprotima 1.000 0.271 0.799 0.990 0.987 0.989 0.425 0.043 0.692
Tamluk
Sub Division
Tamluk 0.242 0.048 0.471 0.884 0.601 0.909 0.185 0.518 0.482
Sahid Matangini 0.271 0.000 0.570 0.861 0.557 0.850 0.088 0.464 0.458
Panskura-I 0.411 0.107 0.295 0.937 0.381 0.787 0.242 0.457 0.453
Panskura-II 0.234 0.033 0.204 0.721 0.031 0.446 0.225 0.471 0.296
Moyna 0.385 0.261 0.541 0.778 0.861 0.979 0.120 0.423 0.545
Nandakumar 0.368 0.115 0.536 0.835 0.781 0.947 0.205 0.396 0.524
Nandigram-III 0.199 0.057 0.803 0.854 0.924 0.966 0.148 0.267 0.527
Haldia
Sub Division
Mahisadal 0.263 0.081 0.387 0.881 0.769 0.863 0.083 0.230 0.445
Nandigram-I 0.201 0.195 0.653 0.881 0.972 0.980 0.142 0.326 0.545
Nandigram-II 0.135 0.108 0.702 0.894 0.982 0.987 0.103 0.078 0.499
Sutahata 0.082 0.362 0.429 0.881 0.719 0.853 0.120 0.169 0.452

5.19
Egra
Sub Division
Patashpur-I 0.323 0.125 0.665 0.871 0.943 0.987 0.157 0.207 0.535
Patashpur-II 0.242 0.091 0.612 0.930 0.922 0.988 0.248 0.307 0.543
Bhagwanpur-I 0.288 0.123 0.466 0.939 0.899 0.974 0.142 0.239 0.509
Egra-I 0.230 0.066 0.685 0.902 0.875 0.986 0.308 0.460 0.565
Egra-II 0.220 0.214 0.557 0.900 0.885 0.980 0.185 0.400 0.544
Contai
Sub Division
Khejuri -I 0.152 0.107 0.615 0.750 0.971 0.984 0.103 0.198 0.485
Khejuri-II 0.143 0.761 0.718 0.938 0.999 0.994 0.350 0.224 0.647
Bhagwanpur-II 0.250 0.164 0.501 0.886 0.905 0.961 0.006 0.183 0.482
Ramnagar-I 0.158 0.104 0.522 0.899 0.747 0.929 0.134 0.563 0.507
Ramnagar-II 0.202 0.098 0.685 0.903 0.816 0.981 0.063 0.392 0.518
Contai-I 0.138 0.100 0.560 0.826 0.886 0.964 0.028 0.205 0.464
Contai-II 0.203 0.053 0.650 0.943 0.929 0.981 0.140 0.306 0.526
Contai-III 0.191 0.091 0.530 0.918 0.944 0.967 0.000 0.150 0.474
5.6. Human Mortality and Morbidity
Human mortality and morbidity is one the most devastating impacts of tropical cyclones. Many lives
are lost at the onslaught of the cyclones and many more are being lost in the subsequent phases –
which can be termed as direct and indirect consequences.
The amount of direct death and injury caused inland by high velocity cyclonic winds is mostly
attributable to the temporary nature of human shelter. Loose roof materials fly off and hit as
projectiles due to wind gusts. Uprooted trees and other objects find it easy to damage shelters made
with temporary materials. Therefore, degree of vulnerability of human life is directly correlated to the
degree of Composite Vulnerability (H) of the Housing stock [Refer Section 5.2.].
On the other hand, indirect death and morbidity takes place due to inadequate aid and relief supply
due to poor road connectivity, pathogenic environment, non-existent heath care facilities and lack of
awareness. The incidence of indirect loss is particularly high on certain age groups – especially
children in the 0-10 age cohort and elderly population with age greater than 60. The magnitude of
indirect loss is more aggravated by socio-economic backwardness.
In this study, we have tried to identify the population at risk and estimate the relative degree of
vulnerability based on several parameters. Composite Index of Vulnerability for the housing stock is
used as a proxy of degree of vulnerability to direct human mortality and morbidity (M'). On the
contrary, degree of vulnerability to indirect human mortality and morbidity (M'') is estimated from the
composite index of vulnerability for physical and social infrastructure (I) along with Composite Index
of Socio-economic vulnerability (S) [Refer Section 5.4. and 5.5.].

5.20
M ′ = H
M ′′ = I . S
where,
H
I
S
i
i
i
i
i
i
i
i
= Composite Index of Vu ln erability of the Hou sin g stock
= Composite Index of Vu ln erability of Physical and Social
= Composite Index of Socio − economic Vu ln erability
Infrastructure
Figure 5-4: Vulnerability mapping of the human life in the coastal districts of West Bengal
Composite Index of Vulnerability to Human Life (M) has also been estimated by taking individual
vulnerability indexes into consideration for both direct (M') and indirect (M'') mortality and morbidity
[Refer Table 5-5 and Figure 5-5].
The functional form specified for aggregation is similar to the one used for estimating Composite
Index of Vulnerability for Housing Stock [Refer Section 5.2.].
Table 5-5: Composite Index of Vulnerability to human life in the coastal districts of West Bengal
Sub-Div. C.D Block
Total
Population in Age Cohort 0-10 &
(Mi')
Population
above 60 yrs
(Mi'') (Mi)
Thakurpukur-
Maheshtala
136903 1.237 47573 0.201 0.967
Bishnupur-I 206370 1.656 71713 0.476 1.855
Bishnupur-II 190636 1.385 66246 0.410 1.466
Budge-Budge(Part-I) 99945 1.565 34730 0.245 1.289
Budge-Budge(Part-II) 173446 1.545 60272 0.280 1.346
Alipore
Sub Division
Baruipu
r
Sub
Divisio
n
Sonarpur 167408 1.578 58174 0.326 1.466
Joynagar-I 219090 1.631 76133 0.412 1.693

5.21
Joynagar-II 209145 1.835 72677 0.521 2.133
Kultali 187989 1.997 65326 0.701 2.749
Baruipur 351439 1.540 122125 0.259 1.298
Bhangore-I 204380 1.680 71022 0.863 2.721
Bhangore-II 207580 1.635 72134 0.807 2.540
Canning
Sub Division
Canning-I 244627 1.846 85007 0.739 2.658
Canning-II 195967 1.963 68098 1.076 3.632
Basanti 278592 1.963 96810 0.937 3.291
Gosaba 222822 1.977 77430 0.549 2.347
Diamond Harbour
Sub Division
Mograhat-I 228335 1.643 79346 0.710 2.342
Mograhat-II 262092 1.659 91076 0.714 2.370
Mandirbazar 183131 1.732 63638 1.045 3.198
Kulpi 242752 1.860 84356 0.876 2.998
Falta 221695 1.580 77039 0.414 1.651
D-Harbour-I 133366 1.691 46344 0.486 1.910
D-Harbour-II 165233 1.598 57418 0.490 1.828
Mathurapur-I 164650 1.851 57215 0.774 2.745
Mathurapur-II 198281 1.897 68902 0.357 1.805
Kakdwip
Sub Division
Kakdwip 239326 1.802 83165 0.409 1.843
Namkhana 160627 1.929 55817 0.338 1.786
Sagar 185644 1.979 64511 0.385 1.943
Patharprotima 288394 1.989 100216 0.439 2.088
Tamluk
Sub Division
Tamluk 204422 0.731 71036 0.466 0.939
Sahid Matangini 176307 0.794 61266 0.446 0.974
Panskura-I 298139 1.033 103603 0.519 1.312
Panskura-II 256882 0.663 89266 0.280 0.658
Moyna 196502 1.233 68284 0.533 1.541
Nandakumar 229462 0.958 79738 0.423 1.096
Nandigram-III 159914 1.355 55570 0.619 1.825
Haldia
Sub Division
Mahisadal 182191 0.825 63311 0.399 0.941
Nandigram-I 174691 1.542 60705 0.583 1.961
Nandigram-II 104637 1.573 36361 0.261 1.327
Sutahata 106338 0.000 36952 0.457 0.229
Egra
Sub Division
Patashpur-I 151609 1.798 52684 0.611 2.303
Patashpur-II 150551 1.763 52316 0.903 2.926
Bhagwanpur-I 198898 1.549 69117 0.421 1.638
Egra-I 145054 1.739 50406 0.701 2.438
Egra-II 156431 1.513 54359 0.589 1.943
Contai
Sub Division
Khejuri -I 114643 1.563 39838 0.455 1.720
Khejuri-II 117438 1.715 40809 0.826 2.687
Bhagwanpur-II 167551 1.590 58223 0.494 1.829
Ramnagar-I 145413 0.921 50531 0.641 1.372
Ramnagar-II 137369 1.312 47735 0.441 1.454
Contai-I 151706 1.272 52717 0.396 1.337
Contai-II 153065 1.403 53190 0.590 1.824
Contai-III 137349 1.514 47728 0.289 1.340

Chapter Six
Mitigation Strategies and Proposed Measures for the
Districts
6.1. General
The discussions in Chapter 2 lead us to propose the following measures for protecting the lives of the
people in the countryside that are prone to cyclonic hazards.
CHAPTER 6
• Strengthening of existing embankments to protect the enclosed land from inundation and salt
water intrusion.
• Protection of riverbank in the inhabited islands of Sundarbans from eroding away due to
strong river current or wave dash.
• Protection of sea beach of the Medinipur coastal tracts from eroding away due to wave dash
caused by storm surges.
• Regeneration of mangrove in river side of the embankments, if possible, in order to protect
them from the direct fury of storm surges.
• Possible shelter belt plantations in the Medinipur coastal tracts for protecting the beach from
degrading due to natural hazards related to cyclones.
• Possible locations of cyclone shelters to provide refuge to the people of the most vulnerable
zones.
• Possible missing road links that may be constructed to connect vulnerable regions to safer
locations.
Each of these points has been elaborated in the following sections of this chapter.
6.2. Embankments
Kanjilal (2006) has provided a detailed description of the condition of the condition of the
embankments today. The following excerpt has been selected from this reference, with the
permission of the author.

6.2
From a hydrological point of view the islands of the Sundarban, presently under cultivation, should be
looked at as "polders" because the water levels of the surrounding river sections are periodically
higher than the field levels.
Polders require man-made embankments to prevent flooding. The river water in the Sundarban is
saline throughout the year and consequently the damage to the crops of the inundated areas is
severe.
The embankments to be constructed, rehabilitated and maintained should meet two criteria: they
need to be high enough to prevent overflow and they need to be strong enough to prevent bursts and
other forms of damage.
These criteria have their effects on the following issues which are related to the construction and the
maintenance of the embankment:
1. The typical cross-section,
2. The alignment of the embankment and the importance of the “berm” situated between the
river and the embankment,
3. The quality of the construction material,
4. The method of construction,
5. Measures to protect the slope of the embankment
6.2.1. Typical Cross-Section
The cross-section of an embankment is determined by: the field level of the strip of land where the
embankment is built or needs to be built, the required level of the crest of the embankment, the width
of this crest and the gradients of the inner and the outer slopes.
In their proposal to improve and repair the flood protection works in the North-Eastern part of the
Sundarban, the Irrigation Department stated that the islands in this area are flat and that the field
level is +1.80 GTS.
Although at macro level the cultivated areas of the islands are relatively flat, observations reveal that
at micro level there are significant differences in level. These observations are confirmed by farmers,
who moreover reported that according to their experience some islands are lower than others. This
topography is characteristic for land reclaimed in tidal area.

6.3
Beside these differences in level because of the different patterns of sedimentation in the past and
the differences in subsidence, the population has excavated ponds and canals; sometimes for the
purpose of water conservation or the improvement of the drainage system but often these excavation
are the so-called "borrow areas" for the construction of the embankments or for rising parts of their
home yards to build their houses on. Many of these ponds and other excavation are situated close to
the embankment. This means that in case the embankment needs to be shifted, the sub-base of the
dike at more than one location will be significantly lower than field level and consequently the fill
needs to be higher. The required crest level needs to be related to some decisive high water level
with a statistical chance to be reached or exceeded once in a specific number of years.
For industrialised areas in Europe the decisive high water level has a chance of occurrence of once
in 3000 years, in agricultural areas in developing countries this can be once in 10 or 15 years. The
choice what should be the decisive high water level is to a very large extent a matter of policy, taking
in consideration the costs of the protection works on the one hand and the potential damage caused
by incidental flooding on the other hand.
The Irrigation Department adopted a design crest level of 4.80+GTS. Ac-cording to information
collected from the office of the Irrigation Department in Gosaba, there are no Benchmarks on the
islands of their sub-division of which the levels has been established in relation to the Reference
Level of the Sundarban.
For that reason the actual levels of the crests of the existing embankments and those of the
embankments that need to be reconstructed cannot be established properly. Reliable and long
ranging data about water levels in the rivers are also not available. Because of this a discussion
about whether a crest level of 4.80+ is sufficient is not relevant. According to information from the
inhabitants the crest levels of the undamaged embankments are considered to be high enough.
According to the Irrigation Department, the standard width of the crest is 1.50 m, in cases no roads
with a pavement of bricks need to be built over that section of the embankment.
From a technical point of view this width is certainly safe enough and for practical reasons the width
is well chosen as it facilitates transportation along the alignment of the embankment of people and
material, which might be an advantage in cases of a calamity. At many locations and over considerable
lengths however the actual width of the crests is not according to this standard. This is not
because the embankments have been damaged by wave-dash or have been affected by slips
initiated by bank failures including parts of the embankment, but simply because they are not
constructed according to the standard specifications; for whatever reason.

6.4
The standard gradient of the outer slope and the inner slope is according to the specifications of the
Irrigation Department: 2 (horizontal): 1 (vertical). For the riverside slope this gradient is most likely a
practical compromise. Steeper gradients reduce the wave run-up but make the slopes more vulnerable
to erosion by wave-dash. Slopes of 2:1 are usually stable if they are properly constructed.
The soils of the embankments at their landsides will gradually become less saline and grass will start
to grow on the inner slopes, "promoting" these slopes to grazing grounds for cattle and goats. If the
gradient is too steep the cattle will damage the slopes while grazing as can be noticed at many
locations. At a less steep angle the hoofs of the animals act as efficient "compactors", improving the
quality of the embankment, which is important even if it only happens at the inner slope. The gradient
of the landside slope should therefore not be steeper than 2:1 and preferably less. After all, the zone
of the inner slope is reasonably productive when used as grazing ground.
In addition to the remarks made about the actual width of the embankments, which have been
visited, needs to be stated that the gradients of the side slopes of nearly all the inspected
embankments are steeper than required by the specifications of the Department. At the riverside this
was sometimes the result of wave-dash which was not yet repaired, but over considerable lengths
the embankments have been constructed with side slopes of 1:1 or even steeper. For all these
reasons the earthen embankments are less stable than they should be and could be.
6.2.2. Alignment and Berm
Like any other structure made by mankind, an embankment needs to be built on a stable base; if the
foundation fails the structure will be damaged, how solid the structure might have been constructed.
If the base of an embankment is weakened, whatever might be the cause, reinforcement of the
embankment itself will be ineffective.
To guarantee this solid base, the embankment needs to be constructed at a safe distance from the
edge of the river especially if the river banks are not stable and show cavings and slides.
The zone between the embankment and the river, usually indicated as the “outer berm”, is important
for a number of reasons:
• to guarantee the embankment a proper foundation,
• to reduce the velocity of the water flowing close to the embankment during the periods when
the water levels are high,

6.5
• to reduce the destructive force of the waves developed during periods of strong wind,
especially along the Southern banks of the wider rivers,
• to create a zone to plant or replant mangroves or other vegetation tolerating saline water, in
order to increase the reduction of the forces of currents and waves,
• to reduce the chance of occurrence of bank failures by lowering the pressure on the edge of
the river; this pressure can be reduced even more by lowering the level of the berm but the
berm level should remain high enough to be planted or replanted successfully with
mangrove.
In many coastal areas in the tropics and also in the Sunderban proof can be found that a zone of
rough vegetation like mangroves is a very effective and very economic protection against wave dash
during storms. In periods the zone is submerged the hydraulic roughness is so high that the velocity
of the flow over the zone and through the mangroves is practically zero. Consequently all the
sediment in the water will settle, even the suspended clays.
The width of the berm which is required to guarantee a solid base for the embankment depends on
the depth and the shape of the river. Often channels are eroded in the bottom of the rivers, due to the
currents. In the outer curves of the river these channels are close to the river banks endangering the
stability of these banks. To prevent that a possible bank failure includes part of the embankment, the
gradient of the imaginary line between the toe of the outer slope of the embankment to the toe of the
river bank should be equal or flatter than 3(horizontal): 1 (vertical).
Another criterion for the required width of the berm is that the zone (re)planted with mangrove should
be at least 10 meters. Considering the criteria as discussed above many of the embankments in the
Sundarban are too close to the rivers and because of this their stability is at least doubtful.
The Forest Department is implementing a programme of replanting mangroves along the rivers in the
estuary. This programme needs to be encouraged. Some coordination between the Forest
Department and the Irrigation Department in order to select the areas where this reforestation is
required most might be useful.
Within the framework of measures to prevent or to reduce the damage of the embankments attention
need to be given to the many boats in the area. The owners drag these boats on the outer slope of
the embankments and sometimes damaging the vegetation on the berm. It might be advisable to
investigate the possibilities to allocate zones for each village where this can be allowed and other
zones where these practices are prohibited.

6.6
6.2.3. Construction Material
The embankments in the Sundarban are built without using any heavy earth moving equipment.
Transport from the borrow areas where the soils are excavated to the locations where the
embankment is built or repaired is executed by labourers carrying buckets on their heads.
Considering this system of transport and the expectation that the system will remain unchanged in
the coming decade, the embankments have to be constructed with material found close by; at least
the major part of their cross-section.
At some locations excellent Clays or Silty Clays have been found, but at the majority of the soils are
ranging from Fine Sandy Loams to Silty Clay Loams; materials with less resistance against wavedash
and scouring by current. Nevertheless these materials are suitable to be used for the construction
of the embankments provided that they are taken from locations where these soils are
sufficiently matured and properly consolidated. In practice however material to build or to repair the
embankment is taken from the top layers of the berm between the river and the embankment or from
the top soils of the adjacent rice fields, which cohesive qualities are strongly reduced by annually wet
ploughing and puddling. These soils have to be qualified as mud or dried mud.
Mud is a material with almost no cohesion and is less suitable to be used successfully for the
construction of sustainable embankments. (The difference in quality of dried mud and matured loams
can easily be demonstrated by putting a lump of each of the materials in separate buckets of water.
After a couple of hours, even without stirring, there is nothing left from the lump of mud and on the
bottom of the bucket is a layer of sediment. The lump of matured loam will show only small
deformation.)
The quality of an embankment largely depends on the proper choice of the material used for its
construction. The difference in costs per unit length between an earthen embankment and an
embankment of which the outer slope is protected by dry brick pitching is so large that the extra costs
required to build the unprotected earthen bank of proper material are mostly more than justified.
These better soils can often be found below the ploughing zone of the rice fields and in the
embankments (or their remains) stability of which is no longer secured. The soils of the berms need
to be examined carefully. Recent deposits should be avoided. If the soils of the outer berms are good
enough to be used as construction material, the quantities should be taken from the zone closest to
the edge of the river.

6.7
6.2.4. Methods of Construction
The specifications and guidelines for construction as they are formulated by the Irrigation Department
are adequate. However there is a large discrepancy between the embankments as they are designed
and as they are actually constructed. In order to achieve proper embankments quality and quality
control needs to be improved.
It is beyond the scope and the competence of this paper to suggest institutional measures to improve
the supervision and the quality and quantity control but when the ultimate goal is to construct proper
embankment these measures are bound to be taken.
As no contractor likes to work at a loss the costs for the construction of the embankment most likely
will increase when proper supervision and control will be implemented as the present unit prices are
presumably too low to expect that the contractors are able to work according to the specifications
and still make a reasonable profit.
6.2.5 Protection of the Outer Slope
The Irrigation Department has protected the outer slope of the embankments over many kilometers
by dry brick pitching. The construction runs from the crest of the embankment till about 0.5m below
low water level. As already stated earlier the construction is extremely expensive in comparison with
the construction of an unprotected embankment. The cost of protected embankments are estimated
by the Department at Rs. 3100/m, while the cost of the unprotected embankment is estimated at Rs.
200/m. According to Kanjilal (2006), there is no need to provide brick pitching at such a costly rate to
the river side slope of the embankment, but possibly reconstruct the embankments once it is
breached at a much lesser cost.
However, it is felt here that probably the brick pitching becomes unstable due to wave dash because
each brick by itself is too weak to resist the force of the wave dash. On the other hand, it is
suggested that a cluster of bricks may be made by available local materials to increase the total
weight and possible resist the force of the wave dash better.
6.2.6. Retiring of embankments
In certain critical locations, as for example at the shores of sea facing islands or at the concave
bends of the tidal creeks, it is inferred that the embankments would not be stable even after
strengthening. The best option in this case would be to retire or retreat the embankment by a few
tens of meters and provide mangrove plantation, if possible. According to Kanjilal (2006), the second

6.8
embankment shall have to be built with the proper sail as is technically necessary, or rather the best
option would be to excavate out the existing embankment, since the material has withstood the test
of time. The distance of retreat has to be according to a possible stable slope, say at least a
minimum of 3 Horizontal : 1 Vertical, as shown in Figure 6-1.
Figure 6 -1. Recommended minimum distance between the riverbank and embankment
6.2.7. Sluice gates
The sluices are constructed with a sliding gate and a flap gate. The sliding gate is necessary to
prevent outflow of water which is useful for the community of the island. For this, the sliding gate can
be and should be in a closed position except at moments excess water needs to be drained. If the
sliding gate is properly constructed and properly operated, it also can prevent the inflow of saline
water during high tide. The flap gate prevents inflow of water when the sliding gate is not closed on
time or is left open.
The sliding gate is a necessity; the flap is a safety precaution which reduces the discharge capacity
significantly. In theory there are two options to increase the discharge capacity of the sluices without
enlarging the diameter of the culverts, which means the construction of a new structure:
• To remove the flap gate and to rely completely on a proper operation of the sliding gates. In
many countries this option has been chosen in cases that the storage capacity was relatively
large. In periods of heavy rains when spilling is required during series of low tides and
consequently the sliding gate needs to be opened and closed with every tide an extra gate
keeper needs to be called on duty.
• To reduce the negative effect of the flap gate by reducing the weight that pushes on the jet of
water leaving the culvert and which diminishes the discharge capacity of the sluice. This can
be achieved by re-construction of the flap gate structure is such a way that a counter weight

6.9
is attached to the structure. The flap is as strong as it was before the reconstruction, but the
resulting weights much less. Flap gates with counter weights are operational with success in
many countries. While reconstructing the flap gates the distance between the center of the
culvert and the hinge of the flap gate structure should be enlarged.
With the information presently available it is not possible to estimate whether improvement of the
discharge capacity of the existing sluices is still required when the other measures have been taken.
It is also difficult to recommend which of the options should be chosen when some improvement is
required. The first option requires fewer investments but requires an alert organization in charge of
operation and maintenance of the water control system.
6.2.8. Recommendations regarding construction of embankments
In the Sunderban region, it is observed that almost all the islands that have been reclaimed for
habitation over the years (as explained in Chapter 2) are bounded by circuit embankments in order to
protect the people and property settled on the islands. In fact, they protected lands represent more
like the polders of Netherlands. The original embankments (dykes) were constructed without any
proper engineering guidelines and thus the slopes on the riverside and on the landside, embankment
crest width and its elevation were all decided upon repeated human experiences. However, rising
waters of the rivers cause failures of these embankments due to overtopping, sloughing, or slip
failure due to erosion of the base due to river current at its base if it is too close to the river.
Specific recommendation is, therefore, needed based upon certain design considerations. Basic
engineering provides guidelines for the crest width, bank slopes, and material that need to be used
for construction of these embankments. However, the crest width should be decided upon a chosen
maximum rise of the river (or ocean) water that is likely to overtop the embankments. Thus, it is
necessary to know the expected rise of water levels based on previously recorded data. This
requires information about the recurrence interval or return period of the occurrence of sea level rise.
Naturally, this depends upon the repetition of sea level rise due to cyclonic storms.
In this regard, the Bureau of Meteorology Research Centre, Australia, in its Global Guide to Tropical
Cyclone Forecasting, (Chapter 7: Warning Strategies, Section 7.5 Hazard, Vulnerability And Risk
Assessment) mentions about a study of return period of tropical cyclone based on a study of 95 year
data by Jayanthi and Sen Sharma in 1988. The data for West Bengal coastline from the study is
given as under:

6.10
Recurrence interval (in years)
10 25 50 100 200
Maximum wind speed (knots) 90 105 116 125 135
Storm surge height (m) 4.5 6.3 7.8 9.2 10.9
A reasonable recurrence interval for assessing the crest of embankments facing the sea may be
considered as 50 years. Thus, adding a freeboard, one may say that an embankment crest elevation
of 8m above Mean Sea Level may be thought of as safely withstanding the overtopping of surges
that is likely to occur with a recurrence of 50 years.
As for the embankments along the rivers, channels and creeks, the rise of the water levels as a
consequence of a rise of the sea water level due to cyclonic storm surges has to be decided upon
the river hydrodynamics. Considering a rise of 7.8m of the sea (with a recurrence interval of 50
years) causes rise of water levels that is much less as the dynamic nature of the surge is dampened
as it enters the channels and creeks.
From the note of Superintending Engineer, eastern Circle, I&W Department, Government of West
Bengal that was prepared in December 2005, titled “Scheme for the revetment works of the
Embankments of Sundarban Areas in the districts of North & South 24-Parganas”, it is necessary to
provide immediate revetment protection to about 235 kms critical length of embankments in the
Sundarbans out of a total of about 3500 kms. The regions that require immediate attention include:
(a) Sea facing dyke – 17 km, (b) Embankments facing major rivers – 139 km, and (c) Embankments
facing medium rivers – 79 km. It is estimated that the total cost estimate is around Rs. 467.82
Crores. Further, 91 km length out of 225 km length of embankments already protected with
revetment under the scheme “Urgent Development Works of Sundarban” need a thorough
maintenance, which requires a sum of Rs.72.18 Crore. Thus, a total sum of Rs.540.00 Crore is
required in the first phase for protection of the most critical of the Sundarban embankments. The
technical and financial details of the proposal are presented below.
Embankment design
(a) Major rivers to armour the riverside slopes (3:1 to 4:1) of the embankments by providing 32.5
cm thick dry brick pitching / 25 cm thick brick block pitching over a layer of 12.5 cm to 15 cm thick
jhama khoa filter with provision of a brick sausage toe wall.

6.11
(b) Medium rivers to armour the riverside slope (3:1) of embankments by providing 20 cm thick
dry brick pitching over a layer of 10.0 cm to 12.5 cm thick jhama khoa filter with provision of brick
sausage toe wall.
(c) Embankments facing Bay of Bengal to armour riverside slope (5:1) by providing (2.0 m x 1.0
m x 0.3 m) C.C. Block over 15 cm thick layer of jhama khoa filter with provision of brick sausage toe
wall.
Data
(a) For Embankments along Major & Medium Rivers
(i) Average Ground Level = R.L. 2.00 m (GTS)
(ii) Highest High Tide Level = R.L. 4.50 m (GTS) (considering flood season of 1976)
(iii) Average High Tide Level = R.L. 3.80 m (GTS) to 3.00 m (GTS)
(iv) Lowest Low Tide Level = R.L. (-) 1.80 m (GTS) to (-) 1.20 m (GTS)
(b) For Embankments facing Bay of Bengal
(i) Average Ground Level = R.L. 2.00 m (GTS)
(ii) Highest High Tide Level = R.L. (+) 5.40 m (GTS)
(iii) Average High Tide Level = R.L. (+) 4.50 m (GTS)
(iv) Lowest Low Tide Level = R.L. (-) 2.00 m (GTS)
Crest Level
(a)
For Major & Medium Rivers
From the scheme "Urgent Development Works of Sundarban", the height of wave of major rivers has
been taken as 1.60 m. Allowing free board of 0.6 m above wave, the actual free board measured
from H.H.T.L. comes to (1.60 + 0.60) or 2.20 m.
Hence the crest level of the embankment along major rivers = 4.50 m + 2.20 m = 6.70 m
However, for major rivers under Kakdwip Irrigation Division the crest level has been fixed at 7.10 m
(considering the locations of the embankments which are mostly nearer to Bay of Bengal).
The crest level for all the medium rivers has been fixed at 6.40 m (considering the free board above
wave as 0.3 m).
(b)
For Embankments facing Bay of Bengal
As per guidelines of the "National Coastal Area Protection Project" (NCAPP), the height of wave has
been taken as 2.20 m. Allowing free board of 0.60 m above wave, the actual free board measured
from H.H.T.L. comes to (2.20 + 0.60) or 2.80 m.

6.12
Hence, the crest level of the embankment facing of Bay of Bengal or the sea dyke = 5.40 m + 2.80
m = 8.20 m
Crest Width
(a)
For Major & Medium Rivers
Based on "Urgent Development Works of Sundarban" the crest width of the proposed revetted
embankment has been chosen as 3.00 m instead of 1.50 m (for only earthen embankment).
(b)
For Embankments facing Bay of Bengal
As per the provision made in the "National Coastal Area Protection" Scheme, the crest width has
been taken as 5.00 m.
Riverside & Countryside Slope
(a) For Major & Medium Rivers
As per "Urgent Development of Sundarban Works Scheme, For major rivers the R.S. Slope is 4:1 For
medium rivers the R.S. Slope is 3:1
However, in this scheme for major rivers the R.S. Slope has been taken as 3:1 barring some
embankments near Bay of Bengal where 4:1 slope has been adopted.
In all the above cases, the countryside slope has been provided as 2:1.
(b)
For Embankments facing Bay of Bengal
As per suggestion made in the "National Coastal Area Protection " Scheme, the riverside slope
should be 6:1. However, for all practical purposes the same has been kept in this scheme as 5:1.
Of course, the countryside slope will be 2:1 as usual.
Revetment on Riverside Slope
(a) For Major & Medium Rivers
In all the embankments along major rivers the revetment work has been proposed to be done by 32.5
cm thick dry brick pitching / 25 Cm thick brick pitching to be laid over 12.5 cm to 15.0 cm thick jhama
khoa filter as has been provisioned in "Urgent Development Works of Sundarban Scheme executed
earlier and the function of which has proved satisfactory.

6.13
Likewise, in all the embankments along medium rivers the revetment is proposed to be done by 20
cm thick dry brick pitching to be laid over 10 cm thick jhama khoa filter.
In all the above cases, the revetment will be taken 1.50 m to 2.00 m below ground level with
provision of brick sausage toe wall of size 0.60 m x 0.60 m at the end,
(b)
For Embankments facing Bay of Bengal
In this case, the revetment is proposed to be made by laying cast-in-situ cement concrete (1:2:4)
block, each of size (2.0 m x 1.0 m x 0.30 m) over 15 cm thick jhama khoa filter.
The above cement concrete block pitching in R.S. slope will be extended to 2.0 m below ground level
with a provision of brick sausage toe wall of size 0.60 m x 0.60 m at the end.
Above provision has been made as per recommendation of the Technical Committee of Flood
Control Board, West Bengal.
Cross Walls on Slope
Cross walls made of brickwork of width 0.25 m will be provided across the R.S. slope revetment @
15.0 m C/C for making compartments of revetment which will facilitate quick and smooth
maintenance to the pitching work in future. Moreover, it will increase the stability of the revetment as
a whole.
Crest Top Wall
Crest top wall made of brickwork of width 0.25 m will be provided along the riverside face of the crest
edge to protect the earthen crest from the fury of major river wave.
The crest top wall of embankment facing Bay of Bengal will be made by 0.60 m wide brickwork with
corbelling.
Typical cross sections of different embankment sections as proposed by the Irrigation and
Waterways Department are provided in Figure 6-2 to 6-10.

6.14
Figure 6 -2
Figure 6 -3
Figure 6 -4

6.15
Figure 6 -5
Figure 6 -6
Figure 6 -7

6.16
Figure 6 -8
Figure 6 -9
Figure 6 -10

6.17
Benefit cost ratio
Area benefited due to prevention of saline inundation:
362.75 Sq.km under Joynagar Irrigation Division
286.50 Sq.km under Kakdwip Irrigation Division
180.00 Sq.km under Basirhat Irrigation Division
Total
(A)
= 829.25 Sq.krn = 829.25 x 100 Ha = 82,925 Ha
Benefit due to Crop production
Culturable or Cropped Area
= 80% of 82925 Ha = 66,340 Ha
Average Crop production as per Census Report = 25 Quintal per Ha per year
Paddy Crop = 66,340 Ha x 25
= 16,58,500 Quintal
Straw =
1.5 times of 16,58,500 Quintal
= 24,87,750 Quintal
Cost of Paddy =
16,58,500 Qtl x Rs.600.00 per Qtl
= Rs. 99,51,00,000.00
Cost of Straw = 24,87,750 Qtl x Rs.175.00 per Qtl
= Rs. 43,53,56,250.00
Total Cost of Production = Rs. 99,51,00,000.00 + Rs. 43,53,56,250.00
= Rs. 143,04,56,250.00
= Rs.14,304.56 Lakh per year
(B)
Value of damages to embankments due to Breach, Wave Wash etc.
In the year 2001-02
= Rs. 952.57 Lakh
2002-03 = Rs. 790.32 Lakh
2003-04 = Rs. 755.94 Lakh
2004-05 = Rs. 1025.00 Lakh
2005-06 = Rs. 858.00 Lakh

6.18
Total
= Rs. 4381.83 Lakh in 5 years
So average value of damages to embankments per year = Rs. 4381.83 Lakh ÷ 5
= Rs. 876.37 Lakh
Loss due to damage of private homes, cattle, livestock, relief measures Etc. being not readily
available has not been considered in this statement.
Total Benefit per year = (A) + (B)
= Rs. 14,304.56 Lakh + Rs. 876.37 Lakh
= Rs. 15,180.93 Lakh
(C) Annual Expenditure
Capital outlay of the scheme = Rs. 54,000.00 Lakh
Considering annual operation and maintenance cost @ 17% of the
Capital Outlay, yearly expenditure comes to Rs. 9,180.00 Lakh
(D) Benefit Cost Ratio comes to = Rs. 15,180.93 Lakh ÷ Rs. 9,180.00 Lakh
= 1.65 : 1

6.19
Location and cost of proposed new embankments with revetment under Basirhat
Irrigation Division
Block Facing river Mouza
Length (m)
Cost
(Rupees)
Hingalganj Raimongal Ramapur 2000 40400000
Madhabkati 3200 64640000
Jogeshganj 1200 24240000
Hemnagar 2200 44440000
Perghumti 1800 36360000
Hingalganj Kalindi Hingalganj 800 14800000
Singerkati 600 11100000
Chhoto Sahebkhali 1200 22200000
Sahebkhali 1000 18500000
Charalkhali 1000 18500000
Sreedharkati 500 9250000
Malakanghumti 3300 61050000
Samsharnagar 3300 61050000
Sandeshkhali - II Bara - Kalagachhi Tushkhali 1250 23125000
Atapur 3000 55500000
Raimongal Monipur 3000 55500000
Hingalganj Sahebkhali Pukuria 700 8400000
-Do- -Do- 1 No. Amberia 500 6000000
-Do- -Do- Swarupkati 1000 12000000
-Do- -Do- Lebukhali 700 8400000
-Do- -Do- Choto Sahebkhali 800 9600000
-Do- -Do- Putia Mathbari 200 2400000
-Do- -Do- Khejurberia 600 7200000
-Do- Dansa Durgapur 600 7200000
-Do- -Do- Dhanikhali 500 6000000
-Do- -Do- Kumirmari 700 8400000
-Do- -Do- Rupamari 500 6000000
-Do- -Do- Banstala 1200 14400000
Sandeshkhali -II Chotto Kalagachi VangaTushkhali 200 2400000
-Do- -Do- Bermajur 300 3600000
-Do- -Do- Jhupkhali 400 4800000
-Do- -Do- Dhamakhali 1200 14400000
-Do- -Do- Tushkhali 8 Number 750 9000000
-Do- -Do- Dwarikjungle 3 No. 800 9600000
-Do- -Do- Dwarikjungle 7 Number 300 3600000
-Do- -Do- Dwarikjungle 500 6000000
-Do- Ghatihara 5 No. Dwarikjungle 1000 12000000
-Do- Rampur Rampur Jeliakhali 2000 24000000
-Do- -Do- (East & West) Bhanga 2000 24000000
-Do- Tushkhali Tushkhli 1400 16800000
-Do- -Do- Bara Tushkhali 1000 12000000
Sandeshkhali -1 Benti Ghoshpur 500 6000000
-Do- -Do- Kalinagar 2000 24000000
-Do- Ghatihara Netyaberia 500 6000000
-Do- -Do- Bholadhaii (W) 1000 12000000
-Do- Bidyadhari Hatgachi 2000 24000000
-Do- -Do- Kalinagar 400 4800000
-Do- -Do- Khariahat 800 9600000
Type of work
Type II B
250mm thick
Brick Block
Pitching in
4:1 Slope
Type II A
325mm thick
Dry Brick
Pitching in
3:1 Slope
-do-
-do-
-do-
-do-
-do-
-do-
Type - I
200mm thick
Dry Brick
Pitching in
3:1 Slope
-do-
-do-
-do-
-do-
-do-
-do-
-do-
-do-
-do-
-do-
-do-
-do-
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-do-
-do-
-do-
-do-
-do-
-do-
-do-
-do-
-do-
-do-
-do-
-do-
-do-

6.20
-Do- Dansa Hasnabad 1000 12000000
-Do- -Do- Ghatihara 2000 24000000
-Do- -Do- Bara Sehara 1500 18000000
-Do- -Do- Bholakhaii (E) 1500 18000000
Minakhan Bidyadhari Chaital 1500 18000000
-Do- -Do- Mohanpur 800 9600000
-Do- -Do- Bachara 600 7200000
Hasnabad Kantakhali Kharampur 1000 12000000
-Do- Ichamati Sodepur 500 6000000
-Do- -Do- Taki 1500 18000000
Basurhat-1 Ichamati Panitor 2000 24000000
-Do- -Do- Bagundi 1500 18000000
-Do- -Do- Dipmedia 1000 12000000
-Do- -Do- Chowrah 500 6000000
-Do- -Do- Tapa Mirzapur 750 9000000
-Do- - Do- Harishpur 500 6000000
Swarupnagar Ichamati Bajitpur 750 9000000
-Do- -Do- Ramchandrapur 1000 12000000
-Do- -Do- Sajarajpur 750 9000000
-Do- ~Do- Banglani 1000 12000000
Baduria Ichhamati Gandharbapur 1000 12000000
-Do- -Do- Nayabastia 650 7800000
-Do- -Do- Raimonitala 1000 12000000
-Do- -Do- Fatullyapur 1000 12000000
-Do- -Do- Kulia 500 6000000
-Do- -Do- Fulardanga 500 6000000
-Do- -Do- Khargachi 500 6000000
Total 83200 1206855000
Type-I: 200mm thick dry brick pitching in 3:1 slope. Estimated cost around Rs. 18,500 per
meter.
Type of Work-IIA: 325mm thick dry brick pitching in 3:1 slope. Estimated cost around Rs.
18,500 per meter.
Type of Work-IIB: 250mm thick brick block pitching in 4:1 slope. Estimated cost around
Rs. 20,200 per meter.
-do-
-do-
-do-
-do-
-do-
-do-
-do-
-do-
-do-
-do-
-do-
-do-
-do-
-do-
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-do-
-do-
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-do-
-do-
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-do-
-do-
-do-
-do-
-do-
Location and cost of proposed repair to embankments with revetment under Basirhat
Irrigation Division
Block Facing river Mouza Length (m) Cost
(Rupees)
Hingalganj Kalindi Sahebkhali 900 8085600
Charalkhali 800 7187200
Kanaikati 500 4492000
Malekanghumti 800 7187200
Sandeshkhali – II Raimangal Monipur 1000 8984000
Basirhat – I Ichhamati Itenda 500 2704000
Akherpur 1000 5408000
Bagundi 400 2163200
Basirhat 1000 5408000
Tapamirzapur 1000 5408000
Type of work
325 mm
Dry Brick
Pitching
200 mm
Dry Brick
Pitching

6.21
Swaraupnagar Swaraupnagar 100 540800
Tentulia 100 540800
Baduria Ramchandrapur 200 1081600
Kulia 200 1081600
Kabilpur 200 1081600
Punra 300 1622400
Media 500 2704000
Sarfarajpur 1000 5408000
Taki 500 2704000
Hasnabad Dansa Sulkuni Abad 700 3785600
Ichhapur 1000 5408000
Bedemari 800 4326400
Katakhali Bhowanipur 1000 5408000
Sandeshkhali-I Bidyadhari Hatgachhi 2000 10816000
Kanmari 400 2163200
Chaital 1500 8112000
Mohanpur 800 4326400
Bachra 600 3244800
Kalinagar 1600 8652800
Sandeshkhali-II Chhotokalakagchhi 3 number Dwarikjungle 1000 5408000
Dhamakhali 1000 5408000
Rampur 1500 8112000
Bermajur 1300 7030400
Bani-Boalia Jeliakhali 2500 13520000
Rampur Jeliakhali, Bhanga Tushkhali 1700 9193600
Boalia Durgamondap 1000 5408000
Bali Korakati 500 2704000
Chhoto Kalagachhi Bhanga Tushkhali 500 2704000
32400 189523200
Estimated cost of repairs to existing embankment by providing pitching of 325mm of dry brick:
Rs. 8984 per metre length.
Estimated cost of repairs to existing embankment by providing pitching of 200mm of dry brick:
Rs. 5408 per metre length.
Location and cost of proposed new embankments with revetment under Joynagar
Irrigation Division
Block Facing river Mouza Length
Cost Type of work
(m)
Roymongal Gosaba Kumirmari 300 5550000 Type IIA
Gomor Gosaba Amlamethi 300 5550000 -do-
Bidya Gosaba Mathurakhanda 300 5550000 -do-
Roymongal Gosaba Kumirmari 350 6475000 -do-
Roymongal Gosaba Kumirmari 650 12025000 -do-
Gomor Gosaba Amlamethi 1350 24975000 -do-
Bidya Gosaba Mathurakhanda 300 5550000 -do-
Gomor Gosaba Satjelia 900 16650000 -do-
Bidya Gosaba Radhanagar 500 9250000 -do-
Kartal Gosaba Chandipur 1130 20905000 -do-

6.22
Roymongal Gosaba Puinjali 800
14800000
-do-
Gomor Gosaba Sonagaon 500 9250000 -do-
Gomor Gosaba Rangabelia 1,000 18500000 -do-
Puinjali Gosaba Kumirmari 700 12950000
-do-
Gomor Gosaba Amlamethi 500 9250000 -do-
Bidya Gosaba Mathurakhanda 900 16650000 -do-
Roymongal Gosaba Puinjali 1000 18500000 -do-
Bagna Gosaba Kumirmari 1000 18500000 -do-
Rangabelia Gang Gosaba Luxbagan 500 9250000 -do-
Bidya Gosaba Taranagar 800 14800000 -do-
Gomor Gosaba Pakhiralaya 1000 18500000 -do-
Roymongal Gosaba Puinjali 1000 18500000 -do-
Bidya Gosaba Mathurakhanda 1000 18500000 -do-
Bidya Gosaba Bali 1000 18500000 -do-
Puinjali Gosaba Puinjali 700
12950000
-do-
Gomor Gosaba Sonagaon 500 9250000 -do-
Ramgabelia Gosaba Lahiripur 1000 18500000 -do-
Hogol Basanti Basanti 630 11655000 -do-
Hogol Basanti 7 No. Sonakhali 1500 27750000 -do-
Hogol Basanti 6 No. Sonakhali 1500 27750000 -do-
Hana Basanti Kalahazra 1000 18500000 -do-
Baniboalia Basanti Charabidya 500 9250000 -do-
Hana Basanti Sachekhali 300 5550000 -do-
Piprakhali Basanti Kumrakhali 500 9250000 -do-
Matla Basanti Nafarganj-lll 1200 24240000 -do-
Matla Basanti Nafarganj-VI 400 8080000 -do-
Bidya Basanti Birinchibari 2500 50500000 -do-
Bidya Basanti Jyotishpur 750 15150000 -do-
Herodhanga Basanti Jharkhali-IV 1000 20200000 -do-
Matla Basanti Laskarpur 1500 30300000 -do-
Matla Basanti Parbatipur 1500 30300000 -do-
Matla Basanti slafarganj-ll 1500 30300000 -do-
Matla Kultali Deulbari 530 10706000 -do-
Matla Kultali Deulbari 1169 23613800 -do-
Matla Kultali Kaikhali 890 17978000 -do-
Gurakhal Kultali Nagenabad 500 9250000 Type of Work- I
Thakuran Kultali Madhya Gurguria 1250 25250000 Type of Work-ll
Thakkkuran Kultali Bhubaneswari 2350 47470000 -do-
Matla Kultali Dongajorah 860 17372000 -do-
Nabipukur Kultali Deulbari 800 14800000 Type of Work-l
Jaynagar-ll Chuprijhora 500
9250000
Type of Work-IIA
Thakuran Kultali Baikunthapur 1500 30300000 Type of Work-IIB
Mridangabhanga Patharpratima Mahespur 650 12025000 Type of Work-IIA
Jagaddal Patharpratima Sirdharnagar Purba 500 9250000 -do-
Thakuran Patharpratima Sri Patinagar 3000 60600000 Type of Work-IIB
Thakuran Patharpratima purba sri Patinagar 600 12120000 -do-
Jagaddal Patharpratima Sridharnagar 700 12950000 Type of Work-IIA
Dhanchi & Jagaddal Patharpratima Sridharnagar 200 3700000 -do-
Pakhirali Patharpratima Upendranagar 300 5550000 -do-
Mridangabhanga Patharpratima Mahespur 550 10175000 -do-
Pakchara Patharpratima Kuenari 600 11100000 -do-
Thakkuran Patharpratima Dk Kashinagar 600 12120000 Type of Work-IIB
Mridangabhanga Patharpratima Ramnagarabad 400 7400000 Type of Work- IIA
Gobadia Patharpratima Parbatipur 400 7400000 -do-

6.23
Gobadia Kakdwip Dk Kasiabad & Kasiabad 300
5550000
-do-
Saptamukhi Kakdwip Harendramagar 200 3700000 -do-
Vlridangabhanga Patharpratima Indraprostha 800 14800000 -do-
Mridangabhanga Patharpratima Ramganga 700 12950000 -do-
Sibua Patharpratima Achintanagar 800 14800000 -do-
Mridangabhanga Patharpratima Laxmipore 300 5550000 -do-
Raidighi Mathurapur-ll Kumrapara 300 5550000 -do-
Raidighi Mathurapur-ll Kumrapara 200 3700000 -do-
Raidighi Mathurapur-ll (umrapara 500 9250000 -do-
Raidighi Mathurapur-ll Kumrapara 700 12950000 -do-
Mridangabhanga Mathurapur-ll Nandakumarpur 650 12025000 -do-
Mridangabhanga Mathurapur-ll Mohabbatnagar 250 4625000 -do-
Mridangabhanga Mathurapur-ll Mohabbatnagar 90
1665000
Type of Work-IIA
Mridangabhanga Mathurapur-ll Mohabbatnagar 600 11100000 -do-
Pakchara Mathurapur-ll Domkal 900 16650000 -do-
Thakkuran Mathurapur-ll Domkal 500 9250000 -do-
Pakchara Mathurapur-ll Kailashpur 800 14800000 -do-
Thakuran Mathurapur-ll Purba Jaterdeul 700 12950000 -do-
Sutarbag Mathurapur-ll Piprakhali 250 4625000 -do-
Surarbag Patharpratima Dk Roypur 700 12950000 -do-
Matla Canning-l Budhakhali 400 7400000 -do-
Matla Canning-l Belekkhali 200 4040000 Type of Work-IIB
Matla Canning-l Garkhali 250 4625000 Type of Work-IIA
Matla Canning-l Redokhali 1500 27750000 -do-
Matfa Canning-l Golabari 500 9250000 -do-
Matla Canning-l Golabari 200 3700000 -do-
Matla Canning-l Golabari 300 5550000 -do-
Matla Canning-l Budhakhali 1500 27750000 -do-
25590
1329039800
Type of Work-IIA: 325mm thick dry brick pitching in 3:1 slope. Estimated cost around Rs.
18,500 per meter.
Type of Work-IIB: 250mm thick brick block pitching in 4:1 slope. Estimated cost around
Rs. 20,200 per meter.
Location and cost of proposed repair to embankments with revetment under Joynagar
Irrigation Division
SI River Block & P. S. Mouza Length
(in m)
Total Cost (in
Lakh)
1 Puinjali Gosaba Kumirmari 500
4000000
2 Puinjali Gosaba Kumirmari 100
800000
3 Puinjali Gosaba Kumirmari 150
1200000
4 Sarsa Gosaba Kumirmari 250
2000000
5 Sarsa Gosaba Kumirmari 250
2000000
6 Roymangal Gosaba Chimta 400
3200000
7 Puinjali Gosaba Amtoli 300
2400000
8 Bidya Gosaba Taranagar 100
800000
9 Bagna Gosaba Kumirmari 150
1200000
10 Hana Gosaba Sambhunagar 1,000
8000000
11 Gomor Gosaba Rangabelia 200
1600000
12 Gomor Gosaba Uttardanga 400
3200000

6.24
13 Gomor Gosaba Dayapur 500
14 Gomor Gosaba Sonagaon 350
15 Gomor Gosaba Amlamethi 400
16 Gomor Gosaba Bejoynagar 700
17 Rangabelia Gang Gosaba Lahiripur 400
18 Dutta Gosaba Luxbagan 100
19 Bidya Gosaba Mathurakhanda 450
20 Durgadoani Gosaba Arampur 300
21 Matla Kultali Dakshin Garankati 1,000
22 Nabipukur Kultali Gopalganj 800
23 Piyali & Matla Kultali Dongajora 800
24 Piyali Kultali Balaharania 400
4000000
2800000
3200000
5600000
3200000
800000
3600000
2400000
8000000
6400000
6400000
3200000
25 Thakuran Kultali Krishrimohanpur 800 6400000
26 JDongajora Kultali Dongajora 400 3200000
27 JGurakhal Kultali Naganabad 400 3200000
28 Nabipukur Kultali Sankijahan 400 3200000
29 Bidya Basanti Radharanipur 500 4000000
30 Bidya Basanti Godkhali 500 4000000
31 Matla Basanti Kanthalberia 500 4000000
32 Matla Basanti 6 No. Sonakhali 300 2400000
33 Matla Basanti Nafarganj-III 1000 8000000
34 Matla Basanti Nafarganj-IV 1000 8000000
35 Matla Basanti Purandar 1150 9200000
36 Hogal Basanti Ramchandrakhali 500 4000000
37 Baniboalia Basanti Kumrakhali 500 4000000
38 Thakukran & Sibua Patharpratima Paschim Sripatinagar 1000 8000000
39 Pakhirali & Thakura Patharpratima Upendranagar 900 7200000
40 Thakuran Patharpratima Purba Sripatinagar 200 1600000
41 Jagaddal patharpratima Sridharnagar 200 1600000
42 Pakchara Patharpratima Kuemari 400 3200000
43 Mridangadganga Patharpratima Mahespur 150 1200000
44 Saptamukhi Kakdwip Harendranagar 600 4800000
45 JMridangabhanga Patharpratima Laxmipur 500 4000000
46 JMridangabhanga Patharpratirna Laxmipur 500 4000000
47 sibua Patharpratima Achintanagar 500 4000000
48 IMatla Canning Budhakhali 500 4000000
49 Matla canning Budhakhali 200 1600000
50 Matla Canning Madhukhafi 1500 12000000
51 Matla Canning Madhukhali 200 1600000
52 Matla Canning Kripakhali 2000 16000000
53 Raidighi Mathurapur-II Kumrapara 300 2400000
54 Sutarbag Mathurapur-II Chapla 100 800000
55 Mridangabhanga Mathurapur-II Kailashpur 300 2400000
56 Mridangabhanga Mathurapur-II Mahabbatnagar 500 4000000
57 Mridangabhanga Mathurapur-II Mahabbatnagar 300 2400000
58 Thakuran Mathurapur-II Damkal 800 6400000
59 Thakuran Mathurapur-II Damkal 170 1360000
60 Thakuran Mathurapur-II Damkal 680 5440000
61 Pakchara Mathurapur-II Damkal 550 4400000
Total 31,000 248000000
Estimated cost of repairs to existing embankment by providing pitching of 300mm of dry brick:
Rs. 8000 per metre length.

6.25
Location and cost of proposed new embankments with revetment under Kakdwip
Irrigation Division
Block Facing river / sea Mouza Length
(m)
Cost (Rupees)
Type of
work
Sagar Bay of Bengal Bhalat & shibpur 2800 140000000
-Do- -Do- Shidpur 700
35000000
-Do- -Do- Chemaguri 500
25000000
-Do- -Do- Beguakhali 1200
60000000
Sagar Hooghly Sapkhali 2800 70000000
-Do- -Do- Narharipur 800
20000000
-Do- -Do- -Do- 600
15000000
-Do- -Do- -Do- 500
12500000
-Do- -Do- Radhakrishnapur 600
15000000
-Do- Hooghly & Maygolia -Do- 1000
25000000
-Do-
Hooghly & Harindari
Radhakrishnapur (Vitar
300
Plot)
7500000
-Do- Hoogly Fuloubi 1800
45000000
-Do- -Do- Krishnanagar 1700
42500000
Sagar Muriganga Kachuberia 1000 25000000
-Do- -Do- Muriganga 1000 25000000
-Do- -Do- Siikarpur 1500 37500000
-Do- -Do- Gobindapur 1500 37500000
-Do- -Do- Devi - Mathurapur 1200 30000000
-Do- -Do- Mrityunjoy Nagar 1000 25000000
-Do- -Do- Sumati Nagar 1500 37500000
-Do- -Do- Bankim Nagar 1500 37500000
-Do- Hoogly Kastala 2000 50000000
-Do- Muriganga Kachuberia 500 12500000
Pathar Pratima Bay of Bengal Gobardhanpur 2500 125000000
-Do- -Do- -Do- 1500 75000000
-Do- - Do- Sttarampur 2500 125000000
Pathar Pratima Jagaddal Sitarampur 600 15000000
-Do- -Do- -Do- 900 22500000
-Do- Saptamukhi Gobardhanpur 600 15000000
-Do- -Do- Burabaurirtat 800 20000000
-Do- -Do- Indrapur 1500 37500000
-Do-
-Do-
Dakshin / Uttar
1200
Surendraganj
30000000
-Do- -Do- Dakshin Surendraganj 400 10000000
-Do- Curzon Creek Surendraganj 200 5000000
-Do- -Do- Gobindapur Abad 1800 45000000
Pathar Pratima Curzon Creek Choto Rakhaskhali 1000 18500000
-Do- Chaftabonia Gangapur 2000 37000000
-Do- Walls Creek Khetra Mohanpur 600 11100000
-Do- -Do- Brajaballavpur 600 11100000
-Do- -Do- Chatta Rakash Khali 300 5550000
-Do- Jagaddal Indrapur 1200 22200000
-Do-
-Do-
Uttar / Dakshin
500
Surendraganj
9250000
-Do- -Do- Gangapur 300 5550000
-Do- Saptamukhi Radhakrishna 500 9250000
-Do- -Do- Brajaballavpur 500 9250000
-Do- Curzon Creek Brajaballavpur & 1200 22200000
Type III -
C. Concrete
Block in
5:1 Slope
Type III -
Type - III
Type II C
Type II A

6.26
Gobindapur Abad
-Do- -Do- Surendraganj 300 5550000
Pathar Pratima Barchara Hare Krishnapur 1000 12000000
Namkhana Bay of Bengal Patibonia 300 15000000
Type II A
Type III
" " " 400 20000000
" " " 900 45000000
" " " 600 30000000
" " " 600 30000000
" " Laxmipur Abad 800 40000000
" " Baliara (East) 100M 50000000
" " Baliara (West) 450 22500000
" " Kusumtala (W) 1000 35000000
Type II C
Namkhana Muriganga Narayanganj 500 12500000
Bagdanga (W) 600 15000000
Debnagar 250 6250000
Mousuni 550 13750000
Namkhana Saptamukhi Haripur 600 15000000
Type II A
Haripur 400 10000000
Haripur 200 5000000
Haripur 350 8750000
Haripur 500 12500000
Namkhana Saptamukhi Dwariknagar 450 8325000
Type II A
Namkhana Channergang Patibonia 1550 28675000
-Do- Mousuni 400 7400000
Namkhana Hatania Doania Dwariknagar 700 8400000
Namkhana Hatania Doania Namkhana 300 3600000
Kakdwip Jagaddal Nadabhanga 1000 25000000
& Namkhana Budakhali 1000 25000000
Kalinagar 500 12500000
Type I
Type II C
Kalinagar 1000 25000000
Kakdwip Baratala Madhusudanpur 1100 27500000
Kakdwip Hatania Doania Narayaanpur 1000 12000000
Type I
& Namkhana Iswaripur (South) 500 6000000
Kakdwip & Kalnagini Jhangora 300 3600000
Namkhana Ghughudanga Manmathapur 100 1200000
72100 2113950000
Type-I: 200mm thick dry brick pitching in 3:1 slope. Estimated cost around Rs. 12,000 per
meter.
Type of Work-IIC: 250mm thick dry brick block pitching in 4:1 slope. Estimated cost
around Rs. 25,500 per meter.
Type of Work-III: Cement Concrete Block (1:2:4) pitching in 5:1 slope. Estimated cost
around Rs. 50,000 per meter.
Location and cost of proposed repair to embankments with revetment under Kakdwip
Irrigation Division
Block Facing river / sea Mouza Length
(m)
Cost (Rupees)
Type of
work
Prathar
Pratima
Bay of Bengal Sitarampur 2500
20000000
Block

6.27
" Jagaddal " 800 6400000
" Jagaddal " 500 4000000
" Bay of Bengal Gobardhanpur 1000 8000000
" Bay of Bengal Gobardhanpur 1500 12000000
" Saptamukhi Indrapur 500 4000000
" Saptamukhi Indrapur 500 4000000
" Saptamukhi Indrapur 1000 8000000
" Saptamukhi Gobardhanpur & R R T 1750 14000000
" Saptamukhi Brojaballavpur 500 4000000
" Curzon Creek Sobindapur Abadi 1750 14000000
Sagar Bay of Bengal Beguakhali 1200 9600000
" Bay of Bengal Shibpur 800 6400000
" Bay of Bengal Chemaguri 600 4800000
" Bay of Bengal Dhablahat 1500 12000000
" Muriganga Kachuberia 400 3200000
" Muriganga Sumatinagar 500 4000000
" Muriganga Chemaguri 1000 8000000
" Hoogly Fuldubi 950 7600000
" Hoogly Naraharipur 600 4800000
" Hoogly Radhakrishnagar(Bahir Plot) 800 6400000
" Hoogly Radhakrishnagar (Bhitar Plot) 300 2400000
" Hoogly Krishnanagar 900 7200000
" Hoogly Fuldubi 450 3600000
Namkhana Bay of Bengal Patibonia 3000 24000000
" Bay of Bengal Lakashipur Abad 1000 8000000
" Bay of Bengal Baliara (W) 1000 8000000
" Bay of Bengal Baliara (E) 400 3200000
" Muriganga Baliara (E) 700 5600000
Vlousuni, Bagdan &
" Muriganga
1600
Kusumtala (W)
12800000
" Saptarrtukhi Haripur 500 4000000
" Saptamukhi Haripur 750 6000000
" Saptamukhi Haripur 1050 8400000
Namkhana Saptamukhi Iswaripur 400 3200000
Kakdwip Muriganga Kalinagar 1000 8000000
" Banstala Thangora 500 4000000
" Banstala Manmathapur 500 4000000
" Banstala Mrinalnagar 600 4800000
35300 282400000
Pitching
repair work
and Brick
Pitching
Estimated cost of repairs to existing embankment by providing pitching of 300mm of dry brick:
Rs. 8000 per metre length.
General abstract of costs
District
Irrigation
Division
Length of new
revetment (in km)
Length of repairs to
revetment (in km)
Total Cost
(Rupees in Crore)
North 24-Parganas Basirhat 82.20 33.20 141.45
South 24-Parganas Joynagar 71.00 31.00 158.58
South 24-Parganas Kakdwip 72.00 35.00 240.00
Total 540.03

6.28
In order to identify the exact location of the exisiting embankments, the satellite imageries of the
study area were analysed. The LISS-III and PAN imageries were procured from National Remote
Sensing Agency, Hyderabad and interpreted with the help of Regional Remote Sensing Service
Centre, Kharagpur. In the following pages, the False Colour Composite (FCC) images of the entire
area are presented in small segments matching with the Survey of India Topo-sheet extents. The
corresponding sheet numbers are written over every image for easy identification. Overlain on the
FCC images are the existing embankments, marked with different colours, depending upon the
corresponding widths. A second set of digitized figures are also presented, which also mark the
locations where new embankments are proposed by the Irrigation and Waterways Department,
Government of West Bengal.

6.29

6.30

6.31

6.32

6.33

6.34

6.35
Figure 6 -11
Figure 6 -12

6.36
Figure 6 -13
Figure 6 -14

6.37
Figure 6 -15
Figure 6 -16

6.38
Figure 6 -17
Figure 6 -18

6.39
Figure 6 -19
6.2.7. Recommendations for retiring of embankments
The following tables provide a list of sites where embankment has to be retired. This has been
taken from the note of Superintending Engineer, eastern Circle, I&W Department, Government
of West Bengal that was prepared in April 1997.
Basirhat irrigation division
Sl.
No.
Name of Mouza. Name of P.S. Name of River Length (m)
1. Malancha (South) Minakhan Bidyadhari 300
2. Kheriat (North) -do- -do- 500
3. Khariat (South) -do- -do- 300
4. Boania Abad -do- -do- 800
5. Bayamari Abad -do- -d0-- 300
6. Ranigachi Haroa -do- 500
7. Batlia -do- -do- 300
8. Shemla -do- Jagannatdokhal 500
9. Behari -do- -do- 300
10. Uchildah -DO- Burikhal 2000
11. Mallick Bhari -do- -do- 2000

6.40
12. Bachra Abad -do- M at akh al 600
13. Bachra -do- -do- 200
14. Mal Kanghumti Hingalgunj . olindi 2000
15. Gobinda Khali -do- -do- 400
16. Samser Nagar -do- Kalindi 300
17. Pansurnagar -do- -do- 300
18. Gharalkhali -do- -do- 80 0
19. Hingalgunj -do- Ichhamati 100
20. Rampur -do- Raimongal 800
21. Madhabaka -do- -do- 500
22. Rampur Sandeshkhali SahebKhali 200
23. Pakuria -do- -do- 600
24. Gongachha -do- -do- 500
25. Lebekhali -do- -do- 300
26. Amberia No. -do- -do. 500
27. Choto Sahabkhali -do- -do- 500
28. Santea -do- -do- 600
29. Bhandar Khali -do- Goureswar 40'
30 Purba Khajuberia -do- -do- 500
31. ~t Amberia No. 3 -do- -do- 500
32. Kumirmari Hasnabad. Dansa 600
33. Tengtala Hasnabad Dansa 500
34. Dhani Khali -do- Dansa 500
35. Durgapur -do- -do- 700
36. Bhanga Tushkhali Sandeshkhali Rampur 500
37. Parba Paschim Jakhali -do- -do- 400
38. Kalinagar -do- Ghatihara 400
39. Dwarik Jungle -do- Chhoto Kalagachi 500
40. Tushkhali -do- -do- 400
41. Puin jali -do- -do- 500
42. Sulkulin -do- Dansa 400
43. Ghak Khali -do- Bidya 400
44. Ramnagar Bosaba Pthankhali 400
45. Chandipur -do- Kartal 400
46. Surjaberia Circuit Gosaba Gomer 500
47. Gosaba -do- Gomer 500
48. PathanKhali -do- Pthankhali 400
Total length of retired embankment (in meters) = 27,000
Joynagar irrigation division
Sl.
Name of Mouza. Name of P.S. Name of River
No.
Length (m)
1. Purba Sridharpur Patharprotima Thakuran 600
2. Maheshpur &
-do- Mridan gabhanga 750
3.
Kedarpur
Nanda Kumarpur & Dakshin
Joykrishnapur -do- -do- 900

6.41
4. Rajraj Swarup &
Ramnagar Abad -do- Gobadia 600
5. Purna Chandrapur -do- -do- 2000
6. Durba Ghati Kultoli Selemati 400
7. Damkal -do- Pukchara 750
8. KeoraKhali Mathurapur Sutarbag 600
9. Herambagopalpur Kultoli Kumari 200
10. Purbaja Deul Mataurapur Chhatua 650
11. Nalgola -do- Moni 750
12. radhaKantapur -do- -do- 900
13. Radhaballavpur -do-
Th aku r an 700
14. Kaikhali
-do-
-do- Matla. 900
15. Gopalgunj Kultoli Sabipukur 600
16. Madhusudanpur Mathurapur Thakuran 600
17. Dakshin Narayantala -do- Matla 900
18. Khas Kumrakhali -do- Bidyadhari 900
19. Kumari Kultoli
Kuerari 600
Total length of retired embankment (in meters) = 15,000
Kakdwip irrigation division
Sl.
No.
Name of Mouza. Name of P.S. Name of River Length (m)
1. Kastala West Sagore Hooghly. 900
2. Kachuberia -do- Muriganga 750
3. Muriganga -do- -do- 300
4. Sikarpur -do- -do- 750
5. Sumati Nagar -do- -do- 300
6. Lakshipur Abad ( Freasergunj) Namkhana Bay of Bengal 600
7. Haripur -do- Saptamukhi & Sundarika. 600
8. Dakshin Durgapur -do- Chiner 250
9. Debnagar Narayangunj -do- Chiner 300
10. Dwarik Nagar -do- Hatania Donia & Sundarika 750
11. Namkhana -do- -do- 750
12. Sitarampur Patharprotima Jagaddal 400
13. Chhotta Rakhashkhali -do- Curzen Creek 500
14. Sibnagar -do- Jagaddal 500
15. Purba Sripatinagar -do- Thakuran 600
16. Brojoballavpur -do- -do- 600
17. Gobindapurabad -do- -do- 600
18. Ramtanu Nagar Kakdwip Hooghly 600
19. Lakshmipur -do- -do- 600
20. Sib Kabnagar -do- -do- 600
21. Budhakhali -do- -do- 600
22. Iswaripur & Narayanpur -do- Hatania Doania 850
Total length of retired embankment (in meters) = 13,000

6.42
The above recommendations of the total 55 kms of retired embankment shall require land acquisition
of around 1947 hectare costing approximately Rs. 23 Crores as per 1997 price index. Though some
of the acquisition has already been done by now, but considering a gradual rise in land prices, the
cost of acquisition of the remaining land is about Rs. 30 Crore. Construction of these embankments
would require another Rs. 10 Crore.
6.3. Riverbank protection
This is the hard option of protecting a riverbank from failing under erosion. It is seen that the most
critical length of the rivers that need to be protected from failure by bank erosion is the 55 kms
identified in section 8.2 for retirement of the existing embankments. The bank protection has to be
done in a scientific manner, and using local material as much as possible. However, it is felt that hard
protections may be avoided since it may so happen that the protected bank remains safe under the
protection but the other banks which are unprotected start loosing a greater amount of material as a
result. Also the cost would be rather high. Instead, the region that is available as a result of retiring of
embankment may be planted with mangrove saplings as mentioned in the following section.
6.4. Mangrove regeneration
Mangroves have been known to help the coastal belts from the ravaging action of waves as
generated by tsunamis or cyclones. As is well known, and recorded by Sanyal (2006), when Tsunami
struck the Tamil Nadu during December 2004, the areas behind Pichavaram and Muthupet with
dense mangroves suffered fewer human casualties and less damage compared to areas without
mangroves. During October 1999, mangrove forests reduced the impact of a super cyclone that
struck Orissa killing at least 10,000 people and making 7.5 million homeless. The human settlements
behind mangroves did not suffer loss. During the year 1988 the devastating cyclone of Sundarban
damaged most of the embankments. But after the cyclone it was noticed that the embankments that
had either toe line mangrove plantations or natural mangrove buffer had hardly been damaged. The
most stable portions were the embankments where a ring dyke was also constructed and mangrove
regenerated in between them as in the Shikarpur forest campus and its vicinity.
Mangroves are efficient silt trappers and it has been proved that the delta progradation of Sundarban
largely depend on the sediment trapping by the mangroves. The presence of mangroves at the
intertidal flats on foreshore of the embankments also helps in sediment accretion at the base of the
embankments and strengthening it in turn. The dearth of sand in the old Digha sea beach is partially
related to the mangrove clearance of Digha Mohana estuary for a large scale co-operative Fishery

6.43
project. Such sediment deficit ultimately prevents accretion that is so much necessary for the stability
of sea wall or embankments. Mangroves at the foreshore of the creeks cause narrowing of creek
orifices that result in increase of the velocity of water and helping the river channel to maintain the
depth which helps in navigation.
For mass plantation of mangroves, normally Ganwa (Excoecaria a gallocha) short poles are driven to
support vegetative palisades on the riverside slope. The quick sprouting Genwa helps to sustain the
brushwood palisade initially. Then the seedlings of other naturally regenerated mangrove species
take the charge of maintaining the stability of the embankments. Usually, 2 to 3 lines of palisades
along the toe line are structured in a staggered fashion. Seeds of Baen (Avicennia spp) are sown in
the palisade which sprouts to stabilise the embankment. On the upper part of the slope Hental
(Phoenix paludosa) and Genwa seeds are to be sown. In case of very gentle slopes three lines of
mangrove plantations may be raised on the foreshore to protect the embankment. Hental being
monocot have fibrous roots and will protect the embankments if the seeds are sown on the slope by
dibbling. On the leeward side again Phoenix and Coconut should be encouraged to stabilise the
embankments. These two species being freshwater monocot again have fibrous roots, which are
likely to render stability to the embankments.
Application of Geojute and planting of Kaora (Sonneratia apetala) have been extremely successful in
Nayachar Island. In fact on the higher slopes of V-shaped channels terracing the slope and planting
the mangrove prefers application of Geojute. The steeper long slopes at Nayachar were excavated to
form the 1m wide terraces at 2m vertical gaps. The terraces were then covered with tar treated jute
having proper perforations to accommodate the plant saplings. The transplanted mangrove saplings
and hypocotyles found their way upwards through the artificial perforations made on the treated jute
cover. The process helps the plants and hypocotyles from being washed away. In case of gentler
slopes, geo jute is less used. But there can be a use if it is felt that the seeds are likely to be washed
away by the currents or may be vulnerable to grazing damage. To day the initial geo-jute plantations
of Sonneratia apetala of Nayachar has not only made the embankment extremely stable but also has
given rise to natural regeneration of other mangroves like Rhizophore, Bruguiera and Excoecaria
spp.
Raising of mangrove plantation in the char lands that is available in between the embankments and
the river face may help to reduce the impact of wave dash at the time of storm surges generated due
to cyclones. However, such land is not readily available for all the embankments since most of the
embankments have been constructed very close to the river. It is estimated that at most about 10

6.44
percent of the embankments (around 3,00,000 meters) have enough space (at least 100 meters)
strip of land between itself and the riverbank which may be planted with mangrove saplings. Thus,
Area available for planting mangrove saplings: 3,00,000 x 100 = 30000000 sq. meters. = 3000
hectares. As per the estimate of the Sunderban Development Board, plantation of mangrove saplings
costs around Rs. 6500 per hectare. Therefore,
Cost of mangrove plantation: 3000 x 6500 = Rs. 1,95,00,000
Apart from this, an additional area that would be available after retirement of the embankments (as
given in Section 8.2) may be planted with mangrove saplings, at least on a part of the area, if not on
the whole. Thus,
Area available for planting mangrove saplings after retiring 55 kms of embankments is 1947
hectares. Therefore,
Cost of mangrove plantation: 1947 x 6500 = Rs. 1,26,55,500
Thus the total cost of mangrove plantation comes to about Rs. 3,21,55,500, Say, Rs. 3 Crores.
6.4.1. The process of making mangrove plantation from various seeds
The following information regarding the growing of mangroves from seeds is included for
completeness. This has been prepared from the note of Assistant Forest Officer, 24-Parganas South
Division, Sundarban Development Board, West Bengal.
1. Survey: Survey, Demarcation and also making map of the area of Mangrove plantation are
made in February to March and through discussion is made with public arid members of
panchyet about the purpose of mangrove plantation in the region so that the public are
encouraged for protecting the Mangrove plantation.
2. Soil Work: Soil work starts from April and continues till June. This includes:
a) Digging contour trench of size 30cm x 30cm x length, 2 mt. apart and dug out soil is
deposited on the upper side of the trench towards the river - embankment.
b) Digging pits of size 30cm x 30cm x 30cm, 2mt apart in between contom trench. Alluvial
soil is deposited in the pits & Trench during high tides and low-tides in the river & they
become fit for sowing seeds.
3. Seeds: Avicennia (alba,marina,officinalis) Bruguiera (Gyrnnorhiza, parviflora) Ceriops
(decandra, tagal), Xylocarpus(Granatum, makongensis), Heritiera fomes, Phoenies

6.45
paludosa, Rhizophora apiculata,Sonneratia apetala, Nypa fruiticans Aecjiceras
carn.iculatum, Excoecaria aqallocha, Seeds are generally sown. Mostly Avicennia species
are sown all over the area. Then seeds are available in Sundarban Tiger Project and 24-
Parganas(S) Division.
4. Seeds Collection: Ripe and Mature seeds are available in July to September. Only
Avicennia Marina seeds are available in October. Excoecaria agallocha, Nypa fruiticans
seeds are available in January. It is better to collected ripe and meture seeds. Seeds are
collected with the help of fine fishing nets during high-tide & low-tide in Kotal Sometimes
seeds are collected from inside the forest on the river bank during kotal.
5. Stores of Seeds: It is better to procure these seeds & sow immediately as it is not possible
to preserve these seeds for more than 7 to 15 days. However seeds may be preserved for a
year through nursery.
6. Planting: The planting of the various species should be done according to the following
guidelines:
a) Avicennia species are better panted the entire trench at a distance of 50 cm. and on
the upper region which is not watered by tide-water. Ceriops species, Bruguiera spp,
Xylocarpus spp, Excoecaria spp, Heritiera spp, phoenix spp, should be planted in
trench at a distance of 1 mt. and in pit at a distance of 2 mt.
b) On the lower region which is regularly watered by tide water everyday. Sonneratia
apetala Aegiceras Carniculatum Rhizophora apiculata, Nypa fruitecans are planted
in pits. It is better to plant them in Trench at a distance of 2 mt.
c) If the region is under the lower tide and is muddy then three types of Avicennia spp
and Sonneratia apetala may be planted for good plantation.
d) Seeds are generally sown twice or thrice time in a year. There is a time when either
all the seeds are not available or most seeds are carried away by tide.
7. Nursery Seedling: This is to be done in the following way:
a) Direct sowing is done in Nursery beds i.e. Sonneratia apetala.
b) Polypots is filled by the earth in the bed on which Heritiera formes Bruguiera
(Gymnorhiza & parviflora) Ceriops (decandra, tagal), Xylocarpus (Granaturn,
Makongensis), Nypa fruiticans, Rhizophora apiculata etc. are sown.
8. Use of seedlings: Seedlings are used in the following ways::
a) Vacancies are filled in the plantation.

6.46
b) Seedlings are planted during December and January when tides and waves are not
so strong in the river.
Some of the species and their seeding and flowering times are provided in the following table:
Sl. No. Species Local Name Flowering
time
Seedling
time
l. Avicennia Alba Paira Bain April July
2. Avicennia Marina Kalo Bain June October
3. Avicennia Officinalis Jat Bain April July
4. Heritiera Formes Sundari March July
5. Bruguiera Gymnorhiza Kankra April July
6. Bruguiera Paruiflora Ban Bakul April July
7. Xylocarpus Granateria Dhudul April August
8. Xylocarpus Mankongensis Pasur April July
9. Aegiceras Carniculatum Khalsi March July
10. Aegialitis Rotandifolia Tora March July
11. Rhizophora Apiculata Garjan April August
12. Sonneratia Apiculata Keora April September
13. Excoecaria Agollacha Genwa March July
14. Ceriops Decandra Garan March July
15. Ceriops Tagal Math Garan March July
16. Phoenix Paludosa Mental March July
17. Nypa Fruiticans Golpata July February
The growth of the above mentioned species of mangroves (from the first to the fifth year) are as
follows:
Height in metres
Sl.
Species
No.
1 st yea 2 nd year 3 rd year 4 th year 5 th year
1. Avicennia alba 0.89 2.68 2.88 3.55 5.90
2. Avicennia Marina 0.80 2.60 2.80 3.50 5.80
3. Avicennia Officinalis 0.88 2.65 2.85 3.55 5.85
4. Heritiera formes 0.45 0.75 0.86 0.95 1.20
5. Bruguiera Gymnorhiza 0.59 0.88 0.98 1.12 2.00
6. Bruguiera Baruiflora 0.55 0.78 0.91 1.10 1.90
7. Xylocarpus Granatum 0.90 2.55 2.90 3.60 6.00
8. Xylocarpus mankongensis 0.80 1.25 1.40 2.42 2.98
9. Aegiceras carniculatum 0.55 0.65 0.80 0.95 1.15
10. Aeqiceras rotandifolia 0.40 0.48 0.70 0.90 1.05
11. Rhizophora apiculata 0.80 1.25 1.40 2.42 2.98
12. Sonneratia apetala 0.90 2.55 2.90 3.60 6.00
13. Excoecaria agollacha 0.65 0.80 0.90 1.10 1.25
14. Ceriops decandra 0.28 0.43 0.53 0.64 0.75

6.47
15. Ceriops tagal 0.22 0.40 0.50 0.61 1.72
16. Phoenix paludosa 0.40 0.55 0.70 0.85 1.05
17. Nypa fruiticans 0.50 0.60 0.76 0.95 1.20
6.5. Coastal erosion protection
The total length of coastal embankment in West Bengal is about 58 kms stretching from the Orissa-
West Bengal border west of Digha upto the Rasulpur river. It is maintained by the Irrigation and
Waterways Department, Government of West Bengal. The embankment protects the inundation of
inland habitated areas from the wrath of violent cyclonic storms and consequent storm surges.
However, the embankment is not very close to the sea at all places. At Chandpur, for instance, it is
so close to the sea that it has been eroded off along a considerable length. At places like
Shankarpur, the embankment is safe, but a large chunk of coastal shelter belt plantation of Casurina
trees have come under the threat of erosion by the dashing sea waves. The jetty at the same place
has been washed off, and at present some temporary measures have been taken by the Irrigation
and Waterways Department, to reduce the effect of the waves. At Digha, the erosion of sea beach
has been prevented from further recession by providing a very costly revetment using concrete
blocks. But just east of this section, there is severe erosion and a big patch of Casurina shelter belt
plantation is presently under threat of being wiped away. It may be noted that in the past couple of
decades, quite a good area of such plantation has already been devoured by the sea by repeated
wave action and enhanced wave dashes during cyclonic storms.
As such, the severely affected portion of the coastal embankment that is affected by erosion (and
enhanced during occurrences of cyclones) is estimated to be about 20 kms. This is because not all
coastline of West Bengal is affected by erosion. In fact, at Junput, there has been a lot of deposition
and the shoreline has shifted seawards over the years. Anyway, the reach that is affected by severe
erosion needs immediate attention, otherwise valuable land is likely to get lost due to shoreline
recession and consequent loss of human habitated land areas.
A possible solution to counter the sea face erosion is to provide a boulder revetment underlain with
geotextile, as shown in Figure 6-20. This design has been taken from the Manual on the use of Rock
in Hydraulic Engineering published by the Road and Hydraulic Engineering Division of the
Government of Netherlands. It has been tested in many locations along sea faces, though certain
other methods may also prove equally useful.

6.48
Figure 6 -20. Typical coastal revetment sections
The cost of providing this kind of protection would cost nearly 4 Crores per km. Thus, for the
protection of the severely affected sea face of 20 kms as identified in the above paragraphs, an
amount of Rs. 80 Crores is required to be invested.
6.6. Shelterbelt plantation
To protect the settlements along the coast line, especially along the coast of East Midnapore district,
shelterbelt can be provided as wind break. Species like Casurina, Subabul etc which are locally
available serves the purpose effectively. The plantation width and orientation should be guided by the
wind direction and the alignment of the human settlement. Care should be taken that the plantation
is not monoculture but accommodates diverse range of species. Plantation of cash crops, especially
coconut, palm etc will increase the biodiversity of the shelter belt plantation along with increasing
community participation in maintaining them. It has been observed that the landfall of cyclone takes
place for a reach of about 50 kms – out of which approximately 30 km stretch does not have either
any kind of plantation or have depleted over time. The estimated expenditure for plantation of

6.49
shelterbelt (average 100 m width) comprising of Casurina, Subabul and other cash crops for this
stretch will be approximately 1.5 crores ( @ Rs. 50,000 per Ha).
6.7. Cyclone shelters
Post Disaster damage assessment studies indicate that cyclone and consequential flooding claim
many human lives and livestock in the coastal district of the state. Most of the housing stock in this
region is made of temporary roof and wall material – thus being most vulnerable to the high velocity
winds and flooding. Vulnerability of housing stock being the prime reason for loss of human life, there
is a need to provide community cyclone/flood shelters to offset this situation.
Mapping of the vulnerability of human life along with the mapping of cyclone and flood hazards helps
in identifying the priority areas for locating cyclone shelters. 12 CD blocks in the South 24 Parganas
enlisted below are in dire need for community cyclone shelters – as the existing hosing stock is more
vulnerable as well as they are located in areas with very high probability of hazard incidence.
Table 6 -1. House type vulnerability in CD blocks identified for community cyclone/flood shelter
C.D Block
Total no. of
Inhabitated
villages
Population
Average
population
per village
% of
Houses
having
temporary
roof
material
% of
Houses
having
temporary
wall
material
Housing
Vulnerability
Index
Cyclone
Hazard
Level
Proposed
Cyclone
Shelter
(no.s)
Kultali 43 187989 4372 0.971 0.996 1.997 Very high 172
Basanti 65 278592 4286 0.963 0.991 1.963 Very high 260
Gosaba 50 222822 4456 0.964 0.997 1.977 Very high 200
Mathurapur-II 27 198281 7344 0.937 0.996 1.897 Very high 189
Kakdwip 39 239326 6137 0.907 0.992 1.802 Very high 234
Namkhana 38 160627 4227 0.948 0.995 1.929 Very high 152
Sagar 42 185644 4420 0.964 0.997 1.979 Very high 168
Patharprotima 87 288394 3315 0.967 0.998 1.989 Very high 261
Design consideration for a typical Cyclone Shelter
Catcment Area: 2 sq.km approx. or 1000 population, (within 0.75 km travel distance)
[Catchment area for cyclone shelter has been reduced due predominance of creeks and channels
one has to cross to reach them]
Design Capacity: 100 - 120 persons (can be augmented upto 200 – 250 persons by
constructing additional floors). This can be used as only cyclone shelter to accommodate
nearly 1000 persons (@5 sgft per person).
Design Area: 5000 sft (@50 sft per person).

6.50
Plinth Height: min 3.0 m above G.L. [Ground floor stilted]
Location: Preferably on high ground and protected by shelter belt plantation.
Type of Construction: In accordance to the guidelines prescribed in ‘Improving Wind/Cyclone
Resistance - Guidelines’ (1999) by BMTPC (Building Materials and Technology Promotion Council)
[Also refer to the NCRMP Guidelines]
Approximate Cost of construction: Rs. 1.5 million per unit (assuming construction cost of Rs.
300/sft)
Ancillary facilities:
1. Wireless Land Line (WLL)
2. First Aid Kit
3. Preventive health care kit (ORS and other life saving drugs)
4. Safe drinking water storage (At least 1000 liters)
5. Sanitation facility
6. Food reserve for the children, sick and aged population
7. Fuel reserve
Alternative usage: Primary school, mass literacy center, community center, mass awareness
campaign and other public utility purposes.
Total Expenditure: Rs. 245 Crores [construction of 1640 no.s of cyclone shelters @ Rs. 1.5 million]
Construction of Community Bovine Shelter
The loss of bovines (cattle, buffalo, goat etc.) from cyclone and flooding has serious consequences
on the local economy of the rural communities. In addition to the community cyclone shelters for the
human beings, the need for community bovine shelter is also increasingly felt to offset this loss.
Past experiences and indigenous local knowledge reveal that animals do not die due to rain but due
to high velocity wind and gales. A land with an area of approximately 2 acres, located on the high
land is adequate to provide shelter to the bovine population of an average village (assuming bovine
population not exceeding 4000). Often it is wise to construct fish tanks (land area of 8 acres approx.)
next to the bovine shelter so that excavated earth can be used for elevating it to the desired level.
Over this elevated land, casurina and subabul (Leucaena leucocephala) plants are to be raised in
alternate rows at a distance of 2m from plant to plant. In between the rows, Stylos hemata, a
perennial leguminous fodder crop could be grown to augment the fodder needs. Arrangement of this
kind will function as a wind break and also protect the animals in deluge.
The entire task has to be accomplished upon community initiative. It is expected cost of construction
of such typical shelters will be in the range of Rs. 0.75 million including the cost of acquisition

6.51
(assuming land acquisition cost of Rs. 20,000 per acre). The likely income that can be realized from
the fish tank can be in the range of Rs. 0.3-0.5 million, after deducting the cost of investment. This
income stream will help meet the annual maintenance cost of shelters as well as other community
facilities.
Vulnerability of the live stock population as well as the cycle/flood hazard incidence indicate that
construction of community cattle shelter should be given top most priority for 3 CD blocks in South 24
Parganas district – namely Basanti, Gosaba and Patharpratima as reflected in Table 6-2.
Table 6 -2. Inventory of livestock in CD blocks identified for community animal shelter
C.D Block
Inhabitated
Livestock
Asset Value Livestock Cyclone
in Million Vulnerability Hazard
Villages Cattles Buffaloes Goats Poultry Rs
Index Level
Basanti 65 82646 4165 69348 232615 757.56 0.901 Very High
Gosaba 50 83104 1502 83155 282629 762.59 0.907 Very High
Patharprotima 87 91106 834 70183 196705 793.44 0.947 Very High
Total Expenditure: Rs. 15.2 Crores [Construction of 202 cattle shelters @ Rs. 0.75 million]
6.8. Mobility Improvement
Mobility improvement can significantly alter the magnitude of loss. Firstly during the emergency
phase, i.e. during the period for evacuation, rescue, humanitarian assistance – where steps are taken
to save lives and provide essential supplies to those most affected. Secondly, during the recovery
phase for restoration of normalcy – mostly to allocation of manpower and resources to undertake
repair and retrofitting activities. Therefore, it is of enormous importance to upgrade mobility (intraregional
as well as intra regional) of these two coastal districts to increase the coping capacity from
cyclone and flood hazards.
Existing mobility pattern for goods and people indicate predominance of road based modes.
However, in some parts of the South 24 Parganas district waterway navigation is extensively used.
Identification of the CD blocks has been done based on the level of road connectivity along with
degree of hazard proneness, as indicated in the Table 6-3.
Table 6 -3. Existing Transportation infrastructure in CD blocks identified for mobility improvement
C.D Block
Road
Connectivity
Index
Cyclone
Hazard
Level
Unsurfaced
Road
(km) 0 - 5
Km.
No. of inhabited villages
away from metal road
5 - 10
Km.
>10
Km.
No. of
Ferry
Service
Nandigram-I 0.973 Very High Nil 37 25 27 2
Sutahata 0.952 Very High Nil 37 46 3 1
Haldia 0.942 Very High Nil Nil Nil Nil 1

6.52
Khejuri-II 0.931 Very High 235 51 10 Nil 3
Ramnagar-I 0.992 Very High Nil 82 6 4 1
Ramnagar-II 0.931 Very High 75 74 29 5 Nil
Contai-I 0.975 Very High Nil 146 46 1 Nil
Contai-II 0.950 Very High 175 117 22 Nil 3
Kultali 0.965 Very High 318.25 7 14 20 13
Basanti 0.989 Very High 185.8 18 18 18 6
Gosaba 0.987 Very High 266 12 9 29 6
Namkhana 0.969 Very High 308 8 6 Nil 5
Sagar 0.900 Very High 528.43 12 9 4 8
In this study, improvement of the mobility has focused has three key aspects as represented
following.
1. Capacity augmentation and surface quality improvement of existing road links
This is done by upgrading the existing unsurfaced roads to Single lane WBM (Water Bound
Macadam) roads.
Total Expenditure: Rs. 167.3 Crores approximately [Conversion of 4227 kms Unsurfaced
road to WBM roads @ Rs. 0.8 million/km]
2. Identification of missing links
A detailed look into the village level connectivity indicates that some of the villages are yet to
have direct access through surfaced roads. Apart from these, culverts, bridges at key

6.53
location are missing reducing the accessibility of these communities. These missing links are
vital on the aftermath of cyclone/flood for emergency response as well as for faster
restoration of normalcy. In addition to these, this missing links will help induce economic
development of these communities, often residing within the bottom most bracket of the
socio-economic stratum.
Total Expenditure: Rs. 234 Crores [Up gradation of 880 kms Kutcha roads to WBM roads @
1.5 miilion/km + additional 75 percent for construction of bridges and culverts at strategic
locations]
3. Improvement of waterway navigation
There is a need to strengthen the existing waterway navigation facilities given their
importance in some of the CD blocks in the district South 24-Parganas. Damage and
interruption to these facilities are mostly due to storm surge. Up gradation of the Jetty
facilities, protection of the river banks at these locations, improving ingress and egress
facilities as well as locating few more jetties at key locations will improve the overall
accessibility of the region.
Total Expenditure: Rs. 15.4 Crores [Up gradation of 49 jetties @ Rs. 1.5 million +
construction of additional 20 jetties @ Rs. 4 million]

Chapter Seven
Mitigation Strategies and Proposed Measures for
Kolkata and Surroundings
7.1. Present Status of the drainage system
CHAPTER 7
Dr. B.N. De's famous "Kulti Outfall Scheme" was commissioned with some gaps in 1943. Since then,
it has undergone major modifications and expansion to meet the rapid growth of the city's area and
population. Following the partition of the country, the city experienced an unprecedented and
protracted exodus from the east. Drainage lines were obstructed due to habitation. Too much and
rapid urbanisation resulted in inadequate drainage capacities of the channels. The city of Kolkata and
its burgeoning environs became victims of notorious flooding and drainage congestion every year.
Serious thinking started to see if anything can be done to ameliorate the distress of the people. The
outfall channels have been cleared from time to time; the capacities of the pump houses were
increased. But the lone Kultigong remains the ultimate drainage outfall from a much larger area. The
discharge is more but the dry weather flow contains a large quantity of domestic sewage. There is
practically no arrangement for treatment of this sewage. Hence the possibility of sedimentation of the
Kultigong cannot be ruled out. The prevailing tides at the outfall resulted in a sluggish disposal of
drainage water. All the drainage channels, viz. SWF, DWF, Bhangarkata, Bagjola have their outfalls
in Kultigong. The Kolkata Drainage Outfall System along with DWF, SWF, THC channels were
handed over by the Kolkata Municipal Corporation to the I.& W. Department on 01.5.1966. The
different outfalling channels being excavated long back as the carrier of drainage water and sewage
began to deteriorate. With the passage of time, due to heavy pressure under increased population
and other factors, the canals had a dwindling flow, somewhere being almost stagnant, the water
being in a brackish state mixed with toxic materials resulting in environmental and health hazards.
The effluent of the channels does not only contain simply house drainage but a large part of it
contains sewarage, toxic matters from small industries, tanneries and other solid wastes even from
Kolkata Slaughter House in the Town Head Cut Channel. The channel sections being worsened for
years together, disposal of drainage water suffered a setback and the purpose for which these
channels were excavated began to frustrate. The situation took its worst turn during the last week of
September, 1999 when heavy concentrated rainfall of 330 mm. within a period of only 10 hours

7.2
resulted in large scale waterlogging. Water receded slowly, the inadequate drainage capacities of the
channels being one of the main hindrances.
The important locations where waterlogging takes place are shown in the annexed figures. The cross
sections of some of the drainage channels are also shown.
7.2. Past proposals for improvement of drainage of Kolkata
A scheme, titled "Development of Comprehensive Drainage System in Kolkata Metropolitan Areas on
the eastern bank of river Hooghly" was accordingly prepared following the recommendations of a
High Powered Committee under the chairmanship of Dr. P.N. Roy constituted by Govt. of West
Bengal in 1999 following an acute drainage congestion faced during the year. The work is under the
aegeis of Housing Urban Development Corporation (HUDCO) loan assistance procured through
West Bengal Infrastructure Development Finance Corporation (WBIDFC) Ltd. The scheme aims at
better efficiency towards restoring the drainage system in and around Kolkata Metropolis and its
environs as per original design stipulation and to remove the inherent impasse as far as possible.
The scheme includes excavation of DWF, THC - SHC - SWF System, Bagjola Khal, Circular
Beliaghata Khal, Kestopur-Bhangarkata Khal, and Pump House at outfall point at Kulti etc.
7.3. Recommendations for further drainage improvement
The following schemes need to be implemented for proper storm water disposal for the city of
Kolkata and surrounding urbanised areas like Bidhan Nagar and adjacent upcoming new
township of Rajarhat. These schemes have been decided jointly by the Kolkata Municipal
Corporation and the Irrigation and Waterways Department, Government of West Bengal.
1. Construction of additional pumping station at Maniktala within the existing with a force
main delivery leading to the circular canal. Estimated cost: Rs. 6,00,00,000.
2. Construction of lifting station on the bank of Kestopur canal to remove waterlogging at
Maniktala area. . Estimated cost: Rs. 10,00,00,000.
3. Construction of lifting station on the bank of Beliaghata canal to remove waterlogging
near Eastern metropolitan Bye Pass. . Estimated cost: Rs. 4,00,00,000.
4. Construction of a pumping station at the junction of K K tagore street and Strand Bank
Road / Jackson Ghat. Estimated cost: Rs. 5,00,00,000.

7.3
5. Construction of a pumping station at D N Mitra square in ward number 70. Estimated
cost: Rs. 14,00,00,000.
6. Augmentation of drainage pumping stations of the Kolkata Municipal Corporation.
Estimated cost: Rs. 17,00,00,000.
7. Construction of a super-pumping station across the SWF channel near Ghushighata
of a capacity 31 cumecs. Estimated cost: Rs. 18,00,00,000.
8. Construction of pumping stations at outfalls of Kestopur canal and Tolly’s Nullah.
Estimated cost: Rs. 2,00,00,000.
9. Construction of a pumping station near Humanity Hospital at Kalagachhia of a
capacity 13.5 cumecs. Estimated cost: Rs. 1,00,00,000.
10. Construction of a sluice at the junction of Tolly’s Nullah and River Hooghly near
Daighat at Khidderpore. Estimated cost: Rs. 8,00,00,000.
11. Construction of a pumping station near Thakurpukur cancer Hospital on Charial
extentsion. Estimated cost: Rs. 4,00,00,000.
It appears imperative that many of the drainage channels need to be excavated up to their respective
design cross sections. Additionally, there could be a need to widen the canals at some places, due to
the additional expected water discharge load from the upcoming township projects like Rajarhat
which is supposed to discharge partly in the Lower Bagjola Canal and partly into Kestopur Canal.
However, the difficulty could be the acquiring of additional land by the side of the exisiting canals and
an extra amount need to be spent if such a proposal is undertaken. The following details are
provided:
7.3.1. Installation of a pump house of 25.50 m 3 /sec capacity at the out fail point of
Ghushighata
Outfall drainage efficiency will improve accruing the following benefits:
1. To allow the additional discharge coming in the SWF channel.
2. Drainage congestion of heavily populated urban areas will be eased.
3. As the pumps would be operated during tide lockage, chances of siltation would be
reduced.
4. Lowering the FDL in SWF channel during tide lockage.

7.4
5. No adverse effect in draining the drainage discharge on account of rise of low water
level due to rise of river bed.
6. Improvement in environmental condition
7. Economic improvement of the community
The pump house has been considered with future provision for Civil work and Mechanical and
Electrical components for present scenario:
• For Mechanical & Electrical Equipment: The pumping capacity has been considered
for 31.17 m 3 /sec. including standby of 5.67 m 3 /sec.
• Civil Structure: Civil structure is considered to be provided for a pumping capacity of
45.27 m 3 /sec (including standby provision) as below:
Present provision:
Future projection - 10% of 141.0 m 3 /sec:
Total:
31.17 m 3 /sec
14.10 m 3 /sec
45.27 m 3 /sec
The proposed pumping station comprises of the following components:
Inlet arrangement
The Inlet arrangement of Ghushighata pumping station will consist of excavation of inlet
channel, pond and construction of forebay.
Pump house with pumping plant
The proposed pumping station will have following pumps with all matching electrical and control
equipment:
• 5 nos. @ 4.25 m 3 /sec capacity (duty) + 1 standby
• 3 nos. @ 1.42 m 3 /sec capacity (duty) + 1 standby
Space provision for 3 nos. of 4.25 m 3 /sec capacity and 1 no. of 1.42m 3 /sec capacity j proposed to
be kept in the pump house to meet the additional pumping requirement c 14.1 m 3 /sec in future
(beyond 2035).
Space required for construction of pump house is about 60 m x 16 m.

7.5
Outlet arrangement:
Outlet arrangement consists of excavation of outfall channel with construction of energy
dissipating structures with side retaining wail, meeting with the outfall channel.
Power supply arrangement:
Provision for necessary power supply with substation facilities has been considered.
Ancillary facilities
(i) Internal roads (ii) Water supply (iii) Fire fighting equipment (iv) Exhaust fans and other
accessories as required for ventilation purpose & (v) Bridge over outlet channel.
Cost for the proposed pump house is estimated at about Rs. 18.00 Crores, the details of which are
provided in the following table.
A. Mechanical & Electrical Works
Sl. No. Item Unit Quantity Rate in Rs. Amount in Rs.
1 Pumps & Motors 4.25 cumec Set 6 4,750,000.00 28,500,000
2 Pumps & Motors 1.42 cumec Set 4 2,820,000.00 11,280,000
3 Pipes & Fiap Valves No. 10 800,000.00 8,000,000
4 Stop Log Gates, Bar Screen &
L.S. 4,000,000
5
Trash Rack
Gantry Crane Set 1 5,000,000.00 5,000,000
6
Transformer 1 1/6 KV 2.5 MVA (Dry
Set
type)
2 2,500,000.00 5,000,000
7 VCB &VCP Panels L.S. 4,500,000
8 VCB Panel (For S/S) L.S. 3,00,000
9
1000 KVA Transformer (Station
service) Set 1 2,000,000.00 2,000,000
10 Capacitors L.S. 700,000
11 HT Cable / LT Cable / Con. Cable L.S. 4,000,000
12 Incoming Feeder (HT)
L.S.
Included in Item
No. 11
13 Earthing L.S. 186,000
14 Illumination L.S. 1,000,000

7.6
15 LT Panel L.S. 2,200,000
16 Instrumentation L.S. 600,000
17 Communication Facilities L.S. 100,000
18 Miscellaneous Facilities L.S. 367,000
Installation and Commissioning
charges
Mechanical 1,900,000
SubTotal (Rs.) 83,133,000
Add 5% for Contingency (Rs.) 4,156,650
B. Civil Works
Sl. No. Item Unit Quantity Rate in Rs. Amount in Rs.
1 Sump construction No. 15 1,400,000 21, 000, 000
2 Pump house construction m 2 9600 1,330 12,768,000
3 Retaining wails in Fore Bay LS 4,800,000
4 Retaining walls in Energy Dissipator LS 5,000,000
5 Paving of Forebay LS 800,000
6 Paving of Energy Dissipator Bay LS 2,000,000
7
8
9
10
11
Earthwork in Sump, Forebay & Energy
Dissipator bay
LS 2,900,000
Earthwork in inlet Channel with side
and bed lining
LS 6,300,000
Shoring & Sheet Piling for
Construction of Sump and Retaining
LS 5,000,000
Cross Bunds Construction,
maintenance & removal
LS 670,000
Block Pitching on Slope including Toe
Wall up-stream of Forebay
Sq.m 3000 600,00 1,800,000

7.7
12
Excavation of Channel Down Stream
with side & bed lining and protection at LS 5,700,000
13 th Bridge tfdownstream ll i l di th of pump t house ti t m 36 100,000 3,600,000
14 Concrete /Metalled road Sq.m 1200 800,00 960,000
15 Boundary wall m 180 3,000,00
16 Sub-station Building (Electrical) L.S 3,500,000
17 Gates Sq.m 40 1,600,00 64.000
18 Guard posts on road Each 16 1,040 16,640
19 Soil Investigation & Survey LS 100,000
SubTotal 77, 518, 640
Add 5% for Contingency (Rs.) 3,875,932
Total of Civil Works (B) 81,394,572
Grand Total ( A + B)
178,684,222
Say, Rs. 18 Crore
7.4. Recommendations for water conveyance
It has been explained how the river Bidyadhari, which used to convey the sewage and storm
water of Kolkata more than a century back had become choked with sediment and silt over
the years forcing Dr. B N Dey to suggest a 35 km long water disposal channel to the river
Kultigong. It is apparent that the untreated sewage that has been disposed off into the river
Kultigong has caused it to reduce in cross section over the years (Table 3-3). It may not be
very far fetched to imagine that this river is likely to get choked in another 50 years’ time,
unless some action is taken now to correct it. As may be apparent, once the riverbed level of
Kultigong rises, the tidal lockage period is likely to increase due to the rise of the high tide
levels, which has to be countered by setting up further high capacity pumps at the outfall
points of the drainage disposal channels. In the event of a high precipitation (as during a
cyclonic storm) the city of Kolkata and its surroundings discharging storm water through the
Bagjola, Kestopur and SWF channels would face a difficult situation of storm water disposal
and may be waterlogged for more than a day in much of its parts. This is because, the storm
water that would be carried down these channels may have difficulty in discharging into the
Kultigong as its water level is expected to be reigning high at this time by an action of high
tide and storm surge. The effect of the river Kultigong reflecting upon the water disposals of

7.8
Bagjola, Kestopur and SWF channels would finally affect the storm water disposal of the
smaller drainage channels and the storm water sewers of the city of Kolkata, Bidhan nagar
township and the upcoming Rajarhat township.
The recommendations for improving the various segments of storm water conveyance for the
city of Kolkata and its surrounding urbanised areas are provided in the following sections.
7.4.1. Dredging of River Kultigong
The river bed of Kultigong, as has been discussed, needs to be kept low and its cross section
areas maintained at least as the maximum that once was (Table 3-3).
River Kultigong be dredged regularly each year to check further siltation. Considering the
difference in cross sections, it is estimated that maintenance dredging would require an
amount of around Rs. 50 Crores initially. In order to keep the river from further deteriorating,
and additional amount of Rs. 10 Crore has to be spent annually for maintenance dredging.
7.4.2. Dredging of SWF channel
As may be ssen from the cross section of the SWF channel at various places, the present
section is markedly different from the design section. The length of the SWF channel is
around 35 kms and considering the average of Rs. 1 Crore per km (as estimated from the
difference in cross section), an amount of Rs. 35 Crores is required.
7.4.3. Dredging of Bagjola canal
There are two sections of the Bagjola canal, of which the upper section (of length 9 kms)
needs urgent attention. Amongst the drainage area of this canal, there is a large area that
drains out from private dairies. This inducts huge amount of solid waste into the canal.
Considering the average of Rs. 1 Crore per km required for excavation of the canal, it is
estimated that Rs. 9 Crores is required.
The lower Bagjola canal is proposed to drain a large section of the upcoming megacity of
Rajarhat. The agricultural land that the area is today does not contribute much runoff to this
canal. But the future urbanisation is definitely going to increase the runoff to this channel. It is
thus necessary to increase the section of this channel in order to increase its storm water

7.9
carrying capacity. It has been estimated that increasing the section may be difficult since
large chunks of area on both sides of the canal has to be aquired. Instead, if the channel is
made lined with vertical walls, then it would not involve land acquisition. However, the cost of
doing such would incur an estimated cost of around Rs. 2 Crore per km. Considering a length
of around 20 km for the canal that would require lining and construction of vertical side walls,
an amount of Rs. 40 Crore needs to be invested.
7.4.3. Dredging of Kestopur canal
This canal drains a part of the Bidhan Nagar Township, as well as Kolkata. The present
sections show that this also requires excavation up to its design shape. It is estimated that
around Rs. 0.5 Crores (Rs. 50,00,000) may be needed per km for doing this. Considering a
length of 20 km that needs to be excavated for dredging the Kestopur canal, an amount of Rs.
10 Crore is required to be set aside for the work.

Executive Cost Summary of Recommendations
All the projects recommended in this report for mitigating the ravages of cyclones on some districts of
West Bengal and on the city of Kolkata and its adjacent urbanized areas, have been provided in the
following table. The cost estimates are preliminary in nature and the amounts have been rounded off
to respective Rupees in Crores.
Proposals for the districts
Sl. No. Proposal Amount in
Rs. Crore
1 New revetments to existing embankments and repairs to existing
embankments
2 Retirement (land-ward shifting) of existing embankments at critical
locations
540
40
Executive Cost Summary
3 Mangrove plantation at locations between riverbank and
embankments in the areas available to reduce the effect of river
water erosion
4 Coastal protection: Sea facing embankments and beach protection
to counter the effects of wave dash and shoreline recession
5 Shelter belt plantation in the region beyond the sea face to reduce
the energy of the cyclonic storm after landfall
6 Construction of community cyclone/flood shelters at different
locations to serve as refuge to cyclone affected people
7 Construction of community Animal shelters at different locations to
serve as refuge to livestock
8 Construction of road links that may serve to connect regions
presently not properly linked with mainland
9 Up gradation of existing road links to improve the connectivity within
the region
10 Construction of new jetties and up gradation of the existing ones for
improvement in waterway navigation
3
80
2
245
15
234
167
15
Total 1341

Proposals for Kolkata and surrounding urbanized areas
Sl. No. Proposal Amount in
Rs. Crore
1 Construction of pumping systems at different location to rapidly
evacuate accumulated rain water from sudden cyclonic cloudburst;
construction of sluice at mouth of Tolly’s nullah
2 Dredging of final water disposing channel – River Kultigong, which
has reduced in section with time
3 Dredging of the three water conveying channels – Bagjola canal,
Kestopur canal and SWF channel
89
50
94
Total 233
Thus, adding up the costs of the two sub-parts of the above recommendations, it is estimated that an
amount of Rs. 1574 Crore is required for mitigating the effect of tropical cyclonic storms in the state
of West Bengal.

References
Kanjilal (2005) “Sunderbans: Its embankments and related issues, Commemorative Volume on
Embankments of Sundarbans and related issues, Published by the Organising Committee for
Workshop-cum-Seminar on Sundarbans held on July 21, 2005, Kolkata.
Sundarban Statistics (2005) “Eknojorey Sundarban”, in Srikhanda Sundarban, Published by
Deep Prakashan, Kolkata.
References
Ashis Kumar Paul (2002) Coastal Geomorphology and Environment, Published by ACB
Publications, Kolkata.
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Annexure

“……………….Designingadisasterpreparednessplanisimpossiblewithoutknowingtherisk
facinganygivenregion.TheStateofWestBengal,withapproximately290kmsofcoastline,
incurshugelossofhumanlifeandeconomicassetsfromTropicalcycloneandstormsurge
relatedinundation.Tomitigatetheeconomicandsocialimpactsofcyclonehazard,Department
ofDisastermanagement,GovernmentofWestBengal,inassociationwithIndianInstituteof
Technology,Kharagpur,hastakenaninitiativetowardspreparationofComprehensiveRisk
AssessmentandDisasterMitigation Strategies.Amultidisciplinaryapproachhasbeen
atemptedtoaccomplishthiscomplextaskthroughrigorousinteractionofexpertsfromdiverse
backgrounds.Thoughthetaskwhichliesaheadismammothinnature,itisexpectedthatthis
atemptwilbeahumblestepforwardinreducingtheriskofvulnerablecoastalsetlementsfrom
thewrathofnature…………”