Assessing Meghna Riverbank dynamics and morphological changes in Bangladesh using geospatial techniques

Abstract

Riverbank erosion is one of the most frequent natural hazards worldwide. Bangladesh is highly affected by this natural hazard every year. The lower segment of the Meghna River is highly vulnerable to this phenomenon. While previous studies have primarily focused on socio-economic impacts in study area or erosion-accretion detection in other major rivers, this study aimed to investigate the spatiotemporal dynamics of riverbank erosion, bank line shifting, and morphological changes in the Meghna River at Haimchar Upazila, Chandpur. Additionally, the study explored the factors driving erosion and potential mitigation strategies. A combination of primary and secondary data was used, including field surveys and satellite image analysis. Normalized Difference Water Index (NDWI) and unsupervised classification techniques were employed to analyze Landsat images from 1980, 1988, 2000, 2010, and 2021. Morphometric parameters such as river width, sinuosity index, and braided index were quantified to assess morphological changes using cross-sections and equations. Results indicate that the highest erosion (4219 ha) occurred between 1988 and 2000, while the lowest (2218 ha) was recorded from 2010 to 2021. Accretion peaked (4215 ha) between 2000 and 2010 and declined thereafter. Over the 42-year study period, the average annual rates of erosion and accretion were 85 ha/yr and 87.8 ha/yr, respectively. Variations in morphological parameters reflect dynamic channel changes, including the formation of bars and islands. Field surveys identified key erosion drivers and highlighted mitigation strategies relevant to the region. The findings underscore the need for integrated river management and adaptive planning to mitigate the adverse effects of riverbank erosion on local livelihoods. Incorporating social factors into future erosion management frameworks could enhance the effectiveness of mitigation measures. This study provides a foundation for developing targeted interventions and sustainable river management practices.