Delineating the Influence of Erosion and Accretion to Identify the Vulnerable Zone of Embankment Breaching in Gosaba Island, South 24 Parganas, West Bengal, India

This study aims to assess the vulnerable zone of embankment breaching in Gosaba Island using geospatial and quantitative techniques. In this study, multi-temporal Landsat data from 1972 to 2017 were used for delineating shoreline change rate, net shoreline movement (NSM), erosion and accretion area and net areal change for each Gram Panchayats (GP) of the island. The shoreline change rate was calculated using end point rate (EPR) for each GP, and the uncertainty of the shoreline change rate was adjusted by measuring the positional error (+/- 3.58 m yr(-1)). Near about, 704.39 ha of lands in Gosaba Island was highly erosion-prone and almost 303.33 ha of lands was completely washed out in the last 45 years. Gosaba (63.35 ha), Kumirmari (58.09 ha), Bally I (66.82 ha), Bally II (16.29 ha), Lahiripur (51.80 ha) and Satjelia GP (52.98 ha) were facing intensive land loss during 1972-2017. For validation of the result, a rigorous field survey during 2017-2018 was conducted and different forms of riverbank erosion were identified and presented in this study. Besides, GP-wise coastal vulnerability was delineated using three parameters, such as EPR, NSM and area under erosion. The statistical analysis revealed that the southern and eastern parts were highly vulnerable to coastal erosion as compared to the northern part of the island. The temporal tidal fluctuations of Sundarbans' rivers also influence the intensity of coastal erosion. Therefore, the construction and management of embankment in this part of the island is highly challenging and needs a proper strategic framework for the longevity of the embankment. The present research work also suggests some planning measures for the protection of embankments. This research study may help to understand the degree of spatial vulnerability of Gosaba Island to erosion hazards and also encourage coastal planners for strategic planning of coastal zone management and its implementation for better resilience of the island against environmental extremes.

Automated summary

This study assessed the vulnerable zone of embankment breaching in Gosaba Island using geospatial and quantitative techniques, revealing that the southern and eastern parts are more susceptible to coastal erosion compared to the northern part.