Coastal Morphological Changes Due to the Nivar Cyclone on the East Coast of India

Shoreline and beach profiles are the primary factors to quantify changes along the coast which in turn are governed by rising sea level, changes in wave characteristics, littoral drift, and the presence of coastal structures. Morphological models are helpful tools to predict such impacts. A very severe cyclonic storm Nivar made its landfall off the coast of Tamil Nadu in the early hours of the November 26, 2020 [17]. The cyclone brought about a maximum of 246 mm. The SWAN wave propagation model and the XBeach morphodynamics model are used to analyze the coastal morphodynamics during the pre and post-cyclonic periods. The SWAN model describes the propagation of waves from offshore to the surf zone by solving the spectral action balance equation. The morphological variations in the littoral zone are strongly connected with the forcing mechanisms that act on the shore, among which the wave action is the foremost factor. The bed level change is calculated from the beach dune up to 6 m water depth from the numerical model. The initial profile (November 20) considered for the pre-cyclonic results was estimated using XBeach with spectral boundary conditions as an input from the SWAN model. The model is validated with the field-collected near-shore bathymetry data. The results are discussed briefly based on the bed level, sediment movement, and the morphological changes due to the impact of the Nivar Cyclone.