A quantitative analysis of shoreline changes along the coast of Bangladesh using remote sensing and GIS techniques

Abstract

The dynamic shoreline of Bangladesh was analyzed for the last thirty years in this study, in order to identify the positional changes due to erosion and accretion. Remotely acquired, multi-temporal Landsat images, of 30 m resolution and comparable tidal conditions, were collected for the period 1989–2019 at a five-year interval. Shorelines were then manually digitized, and a transect-based analysis was carried out using the Digital Shoreline Analysis System (DSAS) extension in ArcGIS. Rates of shoreline change and net movement along transects were determined for the three different coastal zones of the country. Almost 12,000 transects were cast with 50 m interval, for the whole coast, majority of which showed shoreline retreat. The shoreline variability is found to be the highest in the central zone, with rates of erosion being observed up to ~ 120 m/year and accretion up to ~ 230 m/year. The western zone is found to be retreating steadily over the years, at an average rate of 15–20 m/year, while the eastern zone displayed significant changes only at a few localized sites. A supplementary polygon-based analysis was also carried out in ArcGIS, through which the net area of erosion and accretion was determined for the whole study period. The net area loss is observed to be the highest in central zone (~62 km2), whereas opposite scenario is found in the eastern zone which has gained a net area of around 30 km2.