Assessing the Tidal Influences on the Coastal Erosion-Accretion Processes in the Indian Sundarban Delta using Hydrodynamic Models and Geoinformatics

The Sundarbans is currently a subject of serious concern due to the massive coastline erosion that is responsible for reshaping the geomorphological content of the islands. The coastal islands of the Sundarbans have become more susceptible to sea-level rise, cyclonic storms, and coastal flooding, which further accelerate the process of coastal erosion. Identification of erosion-prone regions is highly essential for integrated coastal zone management. Till date, no scientific study has been done to relate the coastal erosion accretion process with tidal velocity and current direction in the Indian Sundarbans. In this perspective, the present study identifies the erosion-accretion zones in the Indian Sundarbans using Landsat imageries of 2000 and 2020 using geoinformatics. It investigates the impact of tidal velocity and direction on the erosion accretion processes. MIKE 21 two-dimensional hydrodynamic model was simulated to predict tidal velocities and directions. The study finds that the sea-facing islands of the Indian Sundarbans experience the maximum amount of erosion. A significant shrinking of the land area takes place in the Bulchery, Bhangaduiani, and Dalhousie islands. The rates of erosion of these islands are 485.99 m/year, 487 m/year, and 480.65 m/year, respectively. Places with high velocity are found to be erosion-prone, while the rate of erosion significantly varied with the flow directions. Two islands, Bulchery and Dalhousie, on the south-eastern margin of the delta, suffered maximum erosion over the past decades due to the impact of high-velocity currents from the southeast and southwest, respectively. Alternatively, minor accretions were observed along with the sheltered island precincts where velocities were comparatively low. Such studies on the current drive erosion–accretion processes along the delta margin during sea-level rise appear to be of utmost importance for sustainable coastal protection and management.