The flood hazard probability map prepared by the Kerala State Disaster Management Authority (KSDMA), taking into consideration the historical rainfall trends, shows that 92 hospitals and 812 schools in the State would be under threat if a flood similar to the one in 2018 recurs in Kerala. As per another map, based on climate change-induced flood hazard probability, the number of schools and hospitals exposed to floods will be 168 and 1,878, respectively.
Maps showing the exposure of schools and hospitals to varying flood return probabilities were prepared by the agency as part of quantifying the flood hazard probability of Kerala. Taluk-wise maps showing local government boundaries were also created. Since schools and hospitals are local landmarks, these maps will facilitate easy comprehension of the areas that may be affected in the event of floods of different magnitudes, according to officials.
Sekhar L. Kuriakose, member secretary, KSDMA, told The Hindu that though the chances a 2018-like flood occurring again in any given year is just 1%, a return period probability, which provides the estimated time interval between events of a similar size or intensity, cannot be ruled out. It was against this backdrop that the KSDMA has prepared flood hazard probability maps for six return periods — 10, 25, 50, 100, 200 and 500 years — in two different scenarios, historical and climate change.
Two purposes
The climate change-induced probability is by and large used for perspective planning, whereas historical scenarios are more realistic and therefore will be used for disaster management plans at the local level, said Mr. Kuriakose. The United Nations Environment Programme (UNEP), UN GRID and CIMA Foundation supported the KSDMA in producing the flood hazard probability maps.
The project to make flood return probability assessments with the help of the UNEP was finalised during the visit of the Chief Minister to the World Reconstruction Conference in Geneva in 2019. Based on the hydrological simulation of historical and climate change scenarios, coupled with other meteorological inputs, the CIMA Research Foundation and the CIMA Technology Foundation, Italy, modelled the flood return probability over different years (10, 25, 50, 100, 200 and 500). The results were used by the KSDMA to quantify the exposure of schools and hospitals in the State to varying flood hazard probabilities.
