Estimation of Extreme Water Levels Due to Cyclonic Storms: A Case Study for Kalpakkam Coast

Abstract

Numerical ocean models are considered today as an essential tool to predict spurt in the sea level rise and associated inland extent of flooding that could be generated by a cyclonic storm crossing any coastal stretch. For this purpose, the advanced two-dimensional depth-integrated (ADCIRC-2DDI) circulation model based on finite-element formulation is applied for the simulation of surges and associated water levels off Kalpakkam coast. Using the long term inventory of cyclone database, synthesized tracks are deduced for affected coastal districts of Tamil Nadu, a state bordering the Bay of Bengal encompassing the Kalpakkam region. Return periods are also computed for the intensity and frequency of cyclones at each coastal district of Tamil Nadu. Using the ADCIRC-2DDI model, validation of surges and associated water levels generated by the November 2000 cyclone, which had landfall near Pondicherry coast was initially carried out. The simulation exercise exhibits a good agreement with available observations from post-storm survey reports. Considering the importance of Kalpakkam region, extreme water levels are computed based on a 50-year return period data, for the generation of storm surges, associated water levels and extent of inland inundation. Based on experimental evidence, it is advocated that this region could be inundated from produced water levels when pressure deficit exceeds a threshold value of 66hPa. Also it is noticed that the horizontal extent of inland inundation ranges between 1–1.5 km associated with the peak surge.