Geomorphological responses to climate change in the Ganges-Brahmaputra-Meghna Delta: A multi-decadal remote sensing analysis

Abstract

The Ganges-Brahmaputra-Meghna (GBM) Delta represents a major riverine system with limited data availability. This study investigates the morphodynamic behavior of the delta and estuary from 1990 to 2021 by analyzing time-series satellite imagery and comprehensive literature to identify key events and driving factors. The aims of this study are to better understand the geomorphological processes that influence the GBM delta system, identify the physical factors contributing to its formation and, predict future challenges for sustainable development in delta areas. Climatological data (temperature and rainfall) from NASA revealed a rising trend in average annual temperature and fluctuating rainfall patterns across five sites in GBM river system: Sirajganj, Tangail, Rajbari, Chandpur, and Bhola. Cyclone track data were analyzed, and GIS mapping of cyclone intensity and trajectories in the GBM delta was conducted to predict future sustainability challenges. Multi-temporal Landsat imagery from USGS Earth Explorer was analyzed using ArcGIS 10.8 to assess riverbank erosion and accretion. Erosion, accretion, and stable land areas varied across five sites of GBM delta from 1990 to 2020. Sirajgonj and Tangail show major land gains until 2010, followed by severe erosion in 2010–2020, with net losses of −404.33 km² and -497.69 km², respectively. Rajbari gained (+234.66 km²) land in 2000–2010 but saw a reversal with a −143.75 km² loss in the next decade. Chandpur had consistent gains until 2010 but a slight loss (−11.8 km²) afterward. Bhola remained the most stable, maintaining continuous net gains, peaking at +76.83 km² in 2010–2020. NDVI, NDWI, and NDSI data reveals a river-wise gradient. NDVI peaks along the Brahmaputra/Jamuna and Ganges/Padma floodplains and declines toward the Meghna estuary. NDWI delineates persistent surface water, while NDSI shows seaward-intensifying salinity toward the Meghna, indicating elevated coastal vulnerability.These findings serve as a guideline to clarify cause-and-effect relationships in global climate change and anticipate future challenges to the sustainable development of the delta.