Brahmaputra riverbank morpho dynamic changes: A multi-temporal geospatial assessment of erosional and processes in northern Bangladesh

Le résumé fourni par la source

Over thirty years (1994–2024), the braided Brahmaputra River has driven dramatic erosion and accretion in Bangladesh's Rangpur Division in northern Bangladesh, reshaping landforms and livelihoods. Our Normalized Difference Water Index (NDWI)-based satellite analysis identifies three phases: from 1994 to 2004, intense bank collapse and channel migration caused a net loss of 62.69 km 2 ; from 2004 to 2014, sediment deposition—bolstered by embankments and land-management practices—produced a net gain of 101.81 km 2 ; and from 2014 to 2024, renewed fluvial forces and diminished sediment retention led to a further net loss of 32.83 km 2 . Fulchhari emerged as a hotspot of decline, while Ulipur and Chilmari showed alternating erosion–accretion patterns, highlighting localized sediment dynamics. These morphological changes have severe socio-economic impacts: agricultural lands have been swallowed by shifting channels, communities face repeated displacement, and infrastructure, including roads, schools, and flood defenses, remains at risk. By integrating multi-temporal NDWI metrics with Geographic Information System (GIS) mapping, this study moves beyond prior short-term or localized research to offer a comprehensive, longitudinal assessment of the Brahmaputra's geomorphological evolution. Addressing a key research gap, our findings elucidate the interplay of natural hydrodynamics and human interventions over decadal scales and provide essential guidance for sustainable river-bank management, infrastructure planning, and community resilience in one of South Asia's most dynamic fluvial landscapes. • Thirty-Year Analysis with Satellite Imagery : The study spans from 1994 to 2024, providing a comprehensive view of long-term riverbank dynamics using Landsat 5 and 8 imagery with 30-m resolution used to capture detailed spatial changes. The Normalized Difference Water Index (NDWI) was employed to accurately distinguish water from non-water features and track riverbank movement and ArcGIS 10.5 was integral in processing and analyzing the satellite data. • Erosion-Dominated Phase (1994–2004) : During this decade, intense erosion resulted in a net land loss of 62.69 km 2 , underscoring the river's dynamic nature. • Accretion Surge (2004–2014) : A reversal occurred with increased sediment deposition leading to a net land gain of 101.81 km 2 . • Resurgence of Erosion (2014–2024) : The latest decade saw a renewed erosional phase with a net land loss of 32.83 km 2 , highlighting ongoing geomorphological challenges. • Critical Erosion Hotspots : Specific upazilas like Fulchhari, Ulipur, and Chilmari were identified as particularly vulnerable, with Fulchhari experiencing the most significant land loss.

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