Mapping of cyclone induced extreme water levels along Gujarat and Maharashtra coasts: a climate change perspective

Coastal flood mapping associated with tropical cyclone induced extreme water elevations is carried out for the Gujarat and North Maharashtra coasts in the perspective of climate projections for the Arabian Sea. The projections are taken into account by enhancing the present cyclone wind intensity by 7% and 11% based on the IPCC fifth assessment report to study its impact on extreme water elevations and coastal flooding. The coupled ADCIRC + SWAN model is used in this study to map the maximum water elevations resulting from storm surges, astronomical tides, and wind-waves by utilizing the most probabilistic cyclone tracks generated for this region. Results from the study signifies that extreme water elevations ranging between 9.0 and 9.5 m are evident in the Gulf of Khambhat and Kutch under no-climate change scenario, while it enhances to a maximum of 10.0-11.0 m under climate change projections. Maximum extent of coastal inundation is found in the low-lying regions of Great and Little Rann of Kutch, Mumbai, and high-tide mudflats of Bhavnagar. It is notable that climate projections have maximum impact on inundation height, while it is marginal in terms of risk associated with the additional inundation extent.