Impact of sea level rise and coastal slope on shoreline change along the Indian coast

Densely populated coastal zones of India are highly exposed to natural environment. These are impacted by episodic natural events, continuous coastal process, gradually rising sea levels and coexisting human interventions. The present study is an attempt to assess the implication of the sea level rise and coastal slope in the coastal erosion for entire mainland of India. In this regard, two methods were employed to estimate the shoreline change rate (SCR): (1) satellite-derived SCR using the Landsat TM and ETM+ acquired during 1989–2001 and (2) SCR derived by Bruun Rule using the parameters coastal slope and sea level trend derived from satellite altimetry. Satellite-derived SCR has been compared with the shoreline change estimated based on Bruun Rule, revealing a better agreement with each other in terms of trend. Peaks of shoreline retreat calculated using Bruun model and satellite-observed SCR offset by 25–50 km. Offset in these peaks was observed due to net drift towards north in the east coast and south in the west coast of India, revealing the applicability of the Bruun Rule along the Indian coast. The present study demonstrates that coastal slope is an additional parameter responsible for the movement of shoreline along with sea level change. The results of satellite-derived SCR reveal the highest percentage of erosion along West Bengal coast with 70% followed by Kerala (65%), Gujarat (60%) and Odisha (50%). The coastlines of remaining states recorded less than 50% of coasts under erosion. Results of this study are proving critical inputs for the coastal management.