Remote Sensing-Based Geospatial Analysis of Channel Migration Patterns in the Lower Shire Valley of the Shire River, Chikwawa District, Malawi

This study examines the spatiotemporal dynamics of fluvial geomorphology along the Shire River floodplain in Malawi from 1975 to 2023, with emphasis on channel migration, width variation, sinuosity, meander curvature, and sediment budget changes. Utilizing multi-temporal satellite imagery and geospatial analysis, morphometric indicators were quantified across 41 cross-sectional zones over four intervals: 1987–1975, 1999–1987, 2011–1999, and 2023–2011. Results show a clear intensification of lateral channel migration, with several zones exhibiting rates exceeding 4 m/year and R² > 0.90. Channel width expanded significantly—from 4.75 m to 83.64 m—confirmed by repeated measures ANOVA (p < 0.001). Though overall sinuosity change was not statistically significant (p = 0.223), local analyses revealed both meander amplification and channel straightening. The Radius-to-Width ratio consistently exceeded 2.0, indicating persistent bend curvature stability. Sediment budget analysis revealed a transition from net erosion (–181.55 m²) during 1987–1975 to substantial net accretion (+2778.11 m²) by 2023–2011, with a strong linear trend (R² = 0.90). These geomorphic changes are linked to climate variability, extreme flood events, and anthropogenic disturbances including land use changes and riverbank modifications. Findings underscore the urgent need for data-driven river basin management, incorporating geomorphological monitoring to support flood risk reduction and sustainable development in the Lower Shire Valley.