06-bioresourcesstatu.. - M. S. Swaminathan Research Foundation

Gulf of Kachchh
Table 5 : Natural wealth of coastal area of Gulf of Kachchh
District Metallic Non-metallic Economically
minerals minerals useful rocks
Kachchh Bauxite Agate,Bentonite, Limestone,
Fireclay,Ochres sandstone
Jamnagar Bauxite Chalk,Gypsum, Limestone
Quartz,Silica-sand
Source: AfehJ; 1995
ii. Geomorphology
The northern plank of the Gulf Le. area from
Jakhau to Kandla has irregular and dissected
configurations. The western half, overlooking the
open Arabian Sea, trends NW-SE and is
dominantly muddy and made up of extensive tidal
fiats. The E-W trending coast that lies inside the
Gulf of Kachchh, is sandy and silty with narrow
beaches. It merges with the Little Rann to the
east. However, the southern plank of the Gulf Le.
the area from Navlakhi to Dwarka, trending E-W,
overlooks the Gulf and shows a crenellated rocky
shoreline with the subtidal zone consisting of
channels, shoals, submerged islands, sand bars,
coral reefs and mangroves.
The beach sands are calcareous and dominated by
bio-casts. The consolidated ancient equivalents of
these biogenic sands are the famous miliolite
rocks. The minerological and petrographical
studies of the submerged intertidal rocks of the
Gulf of Kachchh indicate that they are calcareous
sandstones. The petrology of the rocks, study of
the foraminifera and the nature of insoluble
residue, suggest that these rocks were formed in
an intertidal region of deposition during a period
of lowered sea level (Hashmi et al., 1977).
The Rann is the most remarkable and unique
feature of the Kachchh region, occupying its
northern and eastern parts, forming more than
half of the aerial extent of Kachchh. Mehr & Malik
(1996) give specific account of the formation of
Little Rann (falling between 23'10'N to 23'45'
latitudes and 70'45'E to 71'45'E longitudes) and
owe its origin to the transgression through the Gulf
of Kachchh. According to them the Little Rann
represents the former extension of the Gulf of
Kachchh when the sea:level was high during the
last Holocene transgression.
a. Bathymetry :
The sea slopes gently towards west from the
Arabian sea coast of Kachchh. The sea bed is
Mineral tuels
The tides are of mixed semi-diurnal type (M, type),
with a large diurnal inequality and varying
amplitude, which decreases from north to south
along both the coasts. Because of unique position,
nearness to the Tropic of Cancer, funnel shape of
the Gulf and resonance effects, it experience very
high tides, roughly the highest anywhere along the
Indian coast. The tides, in general, are low on the
open Arabian sea near the Gulf of Kachchh. The
mean high-water spring (MHWS) of 3.47m in Okha
increases to 5.36m at Sikka to 7.31m at Navalakhi.
Longshore currents with low wave energy
dominate the open coasts along the Arabian Sea.
The tidal currents dominate the fiow in Gulf of
Kachchh. Maximum velocities occur during midtide,
which is around 4 knots, associated with high
wave energy.
During the SW monsoon the coastal surface
currents along the West Coast of Saurashtra fiow
alongshore directed northwards. At a distance of
3-5 km from the coast the alongshore current
develops a shoreward component. This
phenomenon is reverses during NE monsoon when
the alongshore-current fiow equator-wards and its
perpendicular component gets directed away from
the shore.
The currents in the Gulf though tidal, are monsoon
in origin. The flow adjusts its directional
orientation with the changing dire( .ion of the wind
affected by changing seasons of the year.
iii. Climate
mostly sandy and muddy. This is
caused by the prograding sediment
from the Indus delta.
Lignite Depth of the Gulf of Kachchh ranges
from a maximum of about 60m at the
mouth to less than 20m at the head of
the Gulf. The topography is very
irregular at the mouth and the central
part of the Gulf and consists of pinnacles and
scarps ranging in height from 6 to 32 m. towards
the head the relief is subdued due to the covering
of fine-grained sediment.
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b. Tides and currents :
The climate in the coastal area of the Gulf of
Kachchh is arid to semi-arid. The northern plank
is extreme arid while southern plank shows semiarid
climate. The .climate is very dryas the
rainfall is always below average every year, which