Numerical Study on Storm Surge and Associated Coastal Inundation for 2009 AILA Cyclone in the Head Bay of Bengal

Storm surge from tropical cyclones leads to extreme coastal flooding along low gradient shorelines, barriers, and deltaic system. Typically low-lying deltaic environment comprises of soft sediments and are densely populated, and these regions are quite dynamic and changes in coastal geomorphology are quite rapid from impact of each cyclone. The horizontal extent of coastal flooding depends on factors such as cyclone intensity, wind speed, and onshore topography. One can expect the worst possible scenario of coastal flooding when the time of storm surge coincides with astronomical high tides. Flooding potential from storm surge is quite high for coastal regions in West Bengal, Bangladesh and Myanmar. High tidal amplitude (≈ 4-5 m) along with complex coastline geometry comprising of several inlets, tidal creeks, and river drainage systems cause differential flooding along the onshore regions. The risk level is quite high as flooding from surge can penetrate the river system and inundate low-lying areas along riverbanks. The current study investigates the scenario of coastal flooding associated with the 2009 Aila cyclone for the West Bengal and Bangladesh regions. The numerical Advanced Circulation (ADCIRC) model estimated the storm surge and associated onshore inundation. The computed maximum storm surge was around 4 m along the Sunderban region. The estimated average inland inundation was about 350 m along the coastal belts and major riverbanks. The inundation occurred along 500 km coastal stretch, with inland penetration distance reaching a maximum of about 600 m at certain low-lying areas in West Bengal and Bangladesh. This study emphasizes the need for inundation mapping in vulnerable coastal areas, having practical significance in coastal disaster management