II. FLOOD LOSS REDUCTION AND REVIEW OF PAST EXPERIENCES
C. Methodology for assessment
5. Risk assessment in flood shelter planningRisk to human lives in the coastal area caused by storm surge flood during a tropical cyclone is of great concern in Bangladesh. More than 700,000 people have been lost in 15 cyclonic surges since 1960. Cyclone shelters standing on stilts are constructed to provide life-saving protection for the population at high risk. In cyclone shelter planning, the saving of lives is the only criteria in contrast to flood control and drainage projects where protection of agricultural damage is the main consideration. As per the Multipurpose Cyclone Shelter Programme of the Government of Bangladesh (BUET and BIDS, 1993), the life of an adult person is at high risk if the depth of flood at a location exceeds 1 metre. In Bangladesh, this criteria would apply to an area of approximately 9100 square kilometers.
A quantifiable measure of risk was developed by Sener and Others (1996) for a Cyclone Shelter Preparatory Study for the Government of Bangladesh where the objective was to develop a project to provide access to safe havens for all inhabitants, both human and animal, of the coastal area at the time of cyclone. A risk index has been devised to assist in ranking of the Mouzas, Unions and Thanas in the coastal area for priority investment. Union and Thana are the lowest and the second lowest tiers respectively in the local government system. A Mouza is a small land revenue unit within the Union. People consider 1.0 to 1.5 km to be the maximum distance that they could be expected to travel to a designated safe-haven at the time of disaster. Hence, the basic land unit that is appropriate for planning purposes is the mouza which has an average area of 2.5 km2, equivalent to a circular area with a 1.8 km diameter (Sener and Others, 1996).
There are 3889 mouzas with a projected population in the year 2001 of
approximately 80 million in the storm surge prone coastal area. A risk
index map of the coastal area is shown in Figure 7. There are 423 mouzas
in the severe risk class and 483 in the very high-risk class having populations
of approximately 2.2 and 1.9 millions respectively (Sener and Other, 1996).
A total of 485 mouzas have been identified as the first priority for the
provision of safe havens. About 11 per cent of the population in the severe
risk category have safe haven provision at present. Taking into consideration
the planned construction of shelters, an additional 1.6 million safe haven
spaces would be required to cater for the severe risk population. The estimated
cost of providing these safe havens in severe risk areas is US $ 240 million
as per Sener and Others (1996).