Coastal vulnerability assessment of India's Purba Medinipur-Balasore coastal stretch: A comparative study using empirical models

Abstract

The 90.20 km coastal stretch extending from India's Subarnarekha estuary (Balasore District, Odisha) to the mouth of the Haldi River (Purba Medinipur, West Bengal) was evaluated. The evaluation was for vulnerability to climate extremes and variabilities (e.g. tropical cyclones, storm surges, and eustatic sea-level rise) resulting in coastal erosion, inundation, salinization and increased biophysical and socio-economic impacts. Coastal vulnerability mapping with respect to coastal hazards was applied to identify and implement risk reduction policies. In order to understand the spatial distribution of physical vulnerability along this coastal stretch, the Coastal Vulnerability Index (CVI) using Gornitz's CVI model and the Analytical Hierarchy Process (AHP) method were applied. These models were run in ArcGIS ver. 10.5 using six geological parameters viz., elevation, slope, bathymetry, coastal geomorphology, shoreline change, and coastal land use and four physical process variables viz. Mean sea level (MSL), mean tidal range, significant wave height, and storm surge height. Both of the models produced very good results. Based on Gornitz's CVI model, it was found that 13.56% of the coastline is highly vulnerable to these hazards, while the AHP model indicated 11.29% of the coast was at high vulnerability. When both models were simulated the same probable inundation extent of two different storm surge scenarios of wave height, viz. ≤ 3 m and≤5 m, the areas estimated to be affected by the surge were 255.22 and 779.59 sq. km, respectively. The coastal blocks of Nandigram-I, Contai-I, Deshopran, and Bhograi were identified as highly vulnerable due to landward erosion and inundation. The study inferred that the combined effect of cyclonic activities and storm surge along with high tide made the coast highly susceptible. This study could help coastal planners, decision-makers, and administrators to prepare a risk management plan for long-term coastal conservation and management.