Integrated geospatial, geotechnical, and hydrologic analysis of bank dynamics in the Kirtankhola River, Bangladesh

The Kirtankhola River is undergoing rapid morphological changes with significant socioeconomic and environmental impacts. This study analyzes its planform dynamics from 1980 to 2023 using satellite imagery and the Digital Shoreline Analysis System (DSAS). We quantified erosion and accretion, bank change rates, sinuosity index (SI), and channel width, and assessed the geotechnical properties of riverbanks and the river’s hydrologic characteristics. Field investigations validated the geospatial analysis and helped identify factors contributing to bank instability. Results show that erosion in the river has predominated over accretion, resulting in a net loss of 739.77 ha and a net gain of 569.67 ha. The left bank was erosion-dominant, while the right bank experienced more accretion. The SI consistently increased from 1.59 in 1980 to 1.78 in 2023, with pronounced bank instability in highly sinuous sections. The mean river width remained relatively stable, but some channel segments showed localized narrowing and widening. These findings suggest that channel morphological adjustments are a major factor in bank instability. Changes in water discharge and bank material properties, as well as human interventions, are also important contributors. This study provides critical insights for zone-wise riverbank protection and management strategies along the Kirtankhola River and similar deltaic rivers worldwide.