Numerical Simulation of Surge Characteristics Considering Sea Level Rise Along the Morpho-Dynamic East Coast of the Meghna Estuary in Bangladesh

The impacts of the morphological changes under different sea level rise scenarios on the storm surge height at the eastern part of the Meghna Estuary have been investigated. Both the newly accreted lands identified from the satellite images and the expected hypothetical newly accreted lands are given 1, 2, and 3 m land elevation arbitrarily. In total five different cyclone tracks: TC-1974, TC-1991, TC-Sidr of 2007, TC-Mahasen of 2013, and TC-Roanu of 2016 are used to generate different cyclonic scenarios with the same strength as TC-1991. With the inclusion of projected SLRs, a total number of 65 scenarios are created to investigate the impact of storm surge in the study area. A coupled Delft3D flow and Delft Dashboard open-source tool and ArcGIS have been applied to simulate, calculate, and visualize storm surge characteristics due to the newly reclaimed lands. Results show that tidal phase has significant impacts on the surge height and duration. The surge water level that starts to increase during the rising tidal phase has produced a sharp peak and short duration and vice versa. The surge height for the different scenarios of the same cyclone track (i.e., Roanu track and Mahasen track) gradually increases from the outer part of the Sandwip Channel toward the inner part of the channel. From numerical simulations of flow fields, it is observed that irrespective of the cyclone track, the mass flux of the cyclonic surges always enters the Sandwip Channel from the south-eastern part of the channel and travels in a the north-western direction toward the Noakhali mainland before reaching the northern part of the Sandwip Island.