Combined Storm Surge and River Flow Simulation for the Hooghly Estuary Along the East Coast of India

A tropical cyclone is a natural disaster that has often led to a substantial threat to lives and properties during its landfall. The storm surges and inland flooding induced by tropical cyclones make the Bay of Bengal coast highly vulnerable. The rivers that discharge into oceans from the inland areas further worsen the flooding effect in the estuary and along some of the stretches of the river. Therefore, understanding the induvial and combined impact of river flows and storm surges becomes essential in evaluating the flood risk. The present study simulates the effects of surges and river flows along the Hooghly River, which is part of the river Ganga flowing through West Bengal and joining the Bay of Bengal. First, storm surges with synthetic tracks of various return periods are chosen to identify the worst-case scenario. Then, different river discharge values are considered to simulate the river-bay interaction using the one-way coupling approach of surge and inland models. The ADCIRC model is adopted to simulate the storm surges using the wind field created from the synthetic track. The inland flooding is simulated using the in-house hydraulic model IITMflo-I2D. The return period discharge values and surge time series from the ADCIRC model are given as upstream and downstream boundary conditions, respectively, in the inland model, IITMflo-I2D. The simulated water level time series from IITMflo-I2D are used to evaluate surge and river flow characteristics along the Hooghly River.