Spatiotemporal Dynamics of Riverbank Erosion and Accretion of the Surma River in Sunamganj District, Bangladesh: A Remote Sensing and GIS-Based Assessment (2000–2025)

Abstract

Riverbank erosion and accretion are important geomorphological processes that continuously modify river channels and adjacent floodplain environments. In Bangladesh, these processes are particularly significant because of extensive alluvial river systems, monsoonal hydrology, sediment dynamics, and frequent flooding. This study investigates the spatial and temporal dynamics of erosion and accretion along the Surma River in Sunamganj District, northeastern Bangladesh, over the period 2000–2025 using remote sensing and Geographic Information System (GIS) techniques. Multi-temporal Landsat satellite imagery was used to delineate river boundaries for different periods, while GIS-based overlay analysis was applied to identify areas of erosion, accretion, and unchanged river extent. The results demonstrate substantial temporal variability. During 2000–2005, accretion was considerably greater than erosion, with reported values of 40.205123 and 0.947521, respectively. Erosion became dominant during 2005–2010 and 2010–2015. A pronounced increase in accretion occurred during 2015–2020, when the reported accretion value reached 968.039589 while erosion declined to 0.224532. During 2020–2025, both erosion and accretion increased substantially, reaching 273.911314 and 975.462243, respectively, indicating intensified channel adjustment and lateral migration. The findings demonstrate that the Surma River is a highly dynamic fluvial system characterized by alternating phases of erosion and deposition. Remote sensing and GIS provide useful tools for monitoring riverbank changes and supporting river management, land-use planning, and erosion-risk reduction.