Assessment of the risk due to storm surge under climate change in the coastal zone of Bangladesh

Abstract

Coastal areas of the world face a range of risk related to climate change. Cyclone and associated storm surge is the most destructive hazard that frequently occurs in Bangladesh and causes enormous suffering to the people of the coastal area. This study has been carried out to assess the hydrological hazard based risk associated with the storm surge due to increase in Sea Surface Temperature (SST) and Sea Level Rise (SLR) in the coastal area of Bangladesh. Increase in SST and SLR will increase surge height which will enlarge the boundary of the Risk Zone (RZ) and High Risk Area (HRA). The maximum surge height was estimated by using an empirical equation. This study illustrates that surge height will increase by about 13 and 33% for 2 and 4°C increase of SST, respectively, for the entire coastal zone of Bangladesh. Increase in surge height indicates greater intrusion distance and larger RZ and HRA. Intrusion distance of the surge water was calculated by using another empirical equation. Study shows intrusion distance will be increased by 6-10 and 18-23% for 2 and 4°C increase in SST, respectively, in the coastal area of Bangladesh. As RZ depends on the possible extent of inland intrusion, increasing intrusion distance will increase the boundary of the RZ as well as HRA. Study demonstrates that RZ will be increased by approximately 16% and 29% for 2 and 4°C increase in SST, respectively. The study also reveals that the HRA will be increased by approximately 20 and 34% for 2 and 4°C increase in SST, respectively. Within the RZ, the areas where cyclone shelter/safe haven are present partially protect the people from the adverse impact of storm surge. It is also found that at present about 75-99% of the population in the coastal districts of Bangladesh are still vulnerable to storm surge risk due to unavailability of the cyclone shelters. The situation will be even worse for the 2°C increase in SST. Residual risk map of the study area shows that Noakhali Sadar, Lakshmipur, Chakaria, Bhola Sadar, Char Fashion, Ramgati, Patiya and Mirsharai thana will be highly susceptible to storm surge risk for the 2°C increase of SST. Moderately vulnerable thanas are Ramgati, Patiya, Mirsharai, Cox's Bazar Sadar, Sitakundu, Banshkhali, Galachipa, Bauphal, Mehendigonj, Hatiya, Mathbaria, Barguna Sadar, Amtali, Burhanuddin, Lalmohon, Roypur, Companiganj, Sonagaji, Sandwip, Chittagong port, Anwara, Maheskhali Teknaf and Ramu. Hence, the populations of those thanas will be even more vulnerable to cyclones/storm surges as a result of climate change. This information will help in making decision for providing safety to coastal population from the adverse impact of climate change.