Impacts of natural and anthropogenic changes on the morphology and shoreline dynamics along the southeast coast of Bangladesh

The southeastern coast of Bangladesh is forming the backbone of Bangladesh’s Blue Economic Zone, where the shoreline types are constantly changing. This research examines the classification of Bangladesh’s southeast coast, changes in shoreline types, and shoreline dynamics from 1990 to 2020. Field investigations, data from Google Earth, satellite images, and statistical analysis have all been carried out, where the transition matrix, sedimentation-erosion, LRR, EPR, and NSM are all used to examine the shifting of coastlines. According to the findings, the overall length of the investigated coastline in 1990 was 295.64 km, with only 11.12 km of human-induced coastline, but the total length of the coastline in 2020 was 281.38 km, with 67.39 km of human-induced coastline. Natural coasts include bedrock, beach, estuary, mangrove, and muddy coastlines; human-induced coastlines include salt fields, constructions, revetment and seawall, ship breaking, and manmade forest coastline. Approximately 60% of the sandy, muddy, and bedrock coastline has been transformed into seawalls, salt fields, and construction shorelines between 1990 and 2020. The changing intensity of coastal length in the study area is highest during 2010–2020, with a value of 0.28%. The analysis shows that over the last 30 years, the study area has lost around 1.06 km² per year and gained 2.35 km² per year, for a total net increase of 38.74 km². Human activities are hastening the process of coastline change, making it critical to protect healthy coastal ecosystems.