Unraveling meandering river morphodynamics: A geospatial investigation of the Madhumati river in Bangladesh

Abstract

The Madhumati River, located on the lower course of the Gorai River, experiences significant erosion and accretion, leading to annual changes in its morphological characteristics within the surrounding catchment area. Our study utilized Landsat satellite data and the ArcGIS platform to investigate the morpho-dynamic alterations and meander-bend formation mechanisms of the Madhumati River. Over a period of 43 years, from 1980 to 2023, we collected cloud-free images from Landsat 3, Landsat 5, Landsat 8, and Landsat 9 using the USGS Earth Explorer. River masks were then generated using the Water Ratio Index (WRI) and Sinuosity Index (SI) methods. In addition, each bend of the river was individually digitized to understand the bend development process, rate of movement, erosion and accretion, changes in river width, and sinuosity. Our findings reveal a gradual increase in river migration over the study period, attributed to significant erosion and accretion occurring at each bend. This research indicates a greater amount of erosion and accretion in river bends, with total sediment deposition exceeding net erosion throughout the study period. Most meandering bends have experienced considerable narrowing, indicating progressive river constriction over time. The construction of the Farakka Barrage contributed to higher sediment deposition from 1980 to 1990, whereas the Kamarkhali Bridge construction provoked an increasing amount of erosion from 1990 to 2010. Sediment deposition increased between 2010 and 2020. The erosion around the downstream bends grew once again when the investigation was carried up until 2023, proving beyond a doubt that the Kalna Bridge construction had an effect on this erosion rise. The increased sinuosity index of bends suggests heightened meandering. These findings have significant implications for engineering and geological practices, including infrastructure maintenance, expansion planning, riverbank protection measures, and agricultural and land management strategies concerning the Madhumati River.