Fluvio-Geomorphic Change of the Padma-Meghna River Course Using the NDWI and MNDWI Techniques

Abstract

This study intends to investigate the fluvial-geomorphic change and erosion-accretion processes of two significant rivers. The 2149 km2 research area's overall erosion and accretion were depicted using multi-temporal Landsat images and NDWI, MNDWI methods to measure and investigate change. However, focus has been placed on four unique sections that are prone to erosion, and the bank migration of the section has been measured in order to depict the actual state of erosion. The Padma-Meghna River eroded approximately 11.0, 77.0, and 13.0 km2 between 1973–1978, 1978–1989, and 1989–1994. However, 78.0 and 48.0 km2 of accretion occurred in the years between 1994 and 1999 and 1999 and 2004. Moreover, between 2004 and 2021, the river's erosional activity was remarkably dynamic compared to deposition. Besides, 64 km2 and 4 km2 of land accretion occurred during 2008–2014 and 2014–2019, while 77 km2 and 68 km2 of land eroded during 2004–2008 and 2019–2021. The overall rates of erosion and accretion are 5.12% and 4.04%, respectively. Statistically, both banks of the Padma River eroded about 2 kilometers from 1973 to 2021. Padma-Meghna confluences are more unstable and susceptible to change. The Meghna's left bank moved 4.5 km east between Goshairhat and Haimchar in 1989, and in 2008, the river shifted 4.8 km west from the river of 1994. In 1989, it moved 5 kilometers east from a previous location between Goshairhat and Haiderganj, and in 2008, it moved 6.3 kilometers west from the 1989 river. The bank migrated 12 kilometers eastward in 2014 from where it was in 2008 through the bar development. The Mehendiganj Upazila's eastern side lost more than 7.4 kilometers between 1973 and 2021, and the current major channel is simply 7.4 kilometers west of the 1973 river. The findings of the dynamic changes might be useful to planners, developers, researchers, and government agencies as they develop and put into practice new development initiatives and river basin management.