Numerical Assessment of Inlet Stabilisation Strategies at the Agniyar River Mouths

The Agniyar river basin is situated in central Tamil Nadu along the coast. Geographically, it lies between 9°55'00"-10°45'00" N latitude and 78°15'00"-79°30'00" E longitude. The present study focuses on solving the problem of inlet closure at the Agniyar river mouths, which detrimentally affects the nearby fishing community. Inlets are short and narrow waterways connecting bays, lagoons, or estuaries with the ocean. In microtidal, wave-dominated environments, inlets usually close seasonally and can cause problems with navigation and poor water quality. This study suggests a suitable solution to keep the inlet navigable and open. The efficiency of these configurations in preventing the closure and ensuring the perennial access is evaluated using Delft 3D FM Suite 2021. A 2D Hydrodynamic model coupled with wave and morphology was set up using Delft3D Flexible Mesh and validated with observed data. The third-generation SWAN model was used to compute the transformation of waves, and the Bijker transport formula was used to compute the sediment transport rates in the model. A yearly study suggests that dredging is a primary solution to overcome the sand bar formation. Results from this study will increase knowledge on sustainable coastal management practices and the livelihoods of fishermen affected by them.