Assessment of the Gradual Emergence of Putney Island, Bangladesh Using Geospatial Techniques

Author: Md Jahidul Alam, Mohammad Azharul Islam, Khan Mohammad Ibtehal, Rahul Mandal, John Christian D. Entia
DOI: doi.org/10.70279/bmj-v1-1094

Bangladesh is a deltaic country, comprising the Ganges-Brahmaputra-Meghna (GBM) River system delta, the largest delta in the world. By accumulating sediment, this active delta continues to expand the shelf regions of Bangladesh, forming new offshore islands in the southern coastal region. Putney Island is a new offshore island in Bangladesh's southwestern coastal zone. This study aims to understand the island's evolution history, spatiotemporal migration, and land cover changes by estimating erosion and accretion, shoreline shifts, and Land Use Land Cover (LULC) changes from 1992 to 2022. Landsat satellite images from 1992, 1995, 2000, 2005, 2010, 2015, 2020, and 2022 have been used in the analysis, which was conducted using ArcGIS 10.5 and ERDAS IMAGINE 2014. At present, the island has a total land area of 5.62 km2. Since 1992, it has shifted dramatically in a northwesterly direction, according to the significant finding of this study; erosion and
accretion processes have influenced changes in land cover patterns. The most significant changes were recorded between 2005 and 2015. Between 2005 and 2010, the island experienced erosion of 3.18 km2 of land, and between 2010 and 2015, the island reached its highest land boundary (7.94 km2) through accretion of 6 km2. Sediment influx might had significant influences during cyclone periods as Bangladesh is a cyclone prone country. Land cover and vegetation studies indicate that the island is covered by 4 km2 of vegetation, mostly mangroves and wetlands in the south. However, despite these dynamic processes, the island has significant potential to contribute to the country's economy.