Cyclone and Storm Surge - Iczmpwb.org

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