Decadal morphological change analysis of the Padma river and local perceptions at Char-Janajat using NDWI and remote sensing

The Padma River’s highly dynamic morphology poses continuous socio-environmental risks in the Bengal Delta. This study addresses a critical local monitoring gap in the Char-Janajat area of Madaripur, filling a void where official government monitoring is currently absent, by presenting a decadal assessment (2012–2022) of riverbank changes and their drivers. Using multi-temporal Landsat imagery and the Normalized Difference Water Index (NDWI) within a GIS framework, we quantified the spatiotemporal extent and rate of riverbank erosion and accretion, complemented by primary data on local perceptions. The analysis revealed a considerable net land gain of 6601.70 hectares over the decade. The average annual accretion rate of 1568.09 ha /year significantly outpaced the erosion rate of 907.92 ha /year. Crucially, the process was found to be highly episodic and non-linear (Erosion R 2 = 0.0466, Accretion R 2 = 0.609), characterized by intense erosion concentrated along the concave (western) bank, followed by rapid deposition along the convex (eastern) bank – a pattern typical of a highly mobile, braided river system. The study identified a critical spatial asymmetry: land loss occurred in established, high-utility areas (settlements), while land gain resulted in unstable, peripheral char formations. This functional disconnect perpetuates community vulnerability. Furthermore, primary data confirms that 95% of local respondents identify external hydrological factors, specifically ‘Sudden release of water from upstream,’ as the overwhelmingly critical hazard driver. The findings provide a significant, localized evidence base, vital for transitioning river management policy from macro-level interventions to site-specific, community-integrated strategies to safeguard the vulnerable Char-Janajat dwellers.