Cyclone and Storm Surge - Iczmpwb.org

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.