摘要：Bangladesh, one of the most disaster-prone countries in the world, has adynamic delta with 123 polders protected by earthen dikes. Cyclone-inducedstorm surges cause severe damage to these polders by overtopping andbreaching the dikes. A total of 19 major tropical storms have hit the coast in the last50 years, and the storm frequency is likely to increase due to climate change.The present paper presents an investigation of the inundation pattern in aprotected area behind dikes due to floods caused by storm surges andidentifies possible critical locations of dike breaches. Polder 48 in thecoastal region, also known as Kuakata, was selected as the study area. AHEC-RAS 1-D–2-D hydrodynamic model was developed to simulate inundation of the polder under different scenarios. Scenarios were developed by consideringtidal variations, the angle of the cyclone at landfall, possible dike breachlocations and sea level rise due to climate change according to the FifthAssessment Report (AR5) of the Intergovernmental Panel on Climate Change (IPCC).A storm surge for a cyclone event with a 1-in-25-year return period was consideredfor all the scenarios. The primary objective of this research was to presenta methodology for identifying the critical location of dike breaching,generating a flood risk map (FRM) and a probabilistic flood map (PFM) for thebreaching of dikes during a cyclone. The critical location of the dike breachamong the chosen possible locations was identified by comparing theinundation extent and damage due to flooding corresponding to the developedscenarios. A FRM corresponding to the breaching in thecritical location was developed, which indicated that settlements adjacent tothe canals in the polders were exposed to higher risk. A PFM was developed using the simulation results corresponding to thedeveloped scenarios, which was used to recommend the need of appropriate landuse zoning to minimize the vulnerability to flooding. The developedhydrodynamic model can be used to forecast inundation, to identify criticallocations of the dike requiring maintenance and to study the effect ofclimate change on flood inundation in the study area. The frequency and intensity of the cyclones around the world are likely toincrease due to climate change, which will require resource-intensiveimprovement of existing or new protection structures for the deltas. The identification and prioritization of the maintenance of critical locations of dikebreaching can potentially prevent a disaster. The use of non-structural tools such asland use zoning with the help of flood risk maps and probabilistic floodmaps has the potential to reduce risk and damage. The method presented inthis research can potentially be utilized for deltas around the world toreduce vulnerability and flood risk due to dike breaching caused by cyclone-induced storm surge.
