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

This study investigates the spatiotemporal dynamics of the Shire River’s fluvial geomorphology from 1975 to 2023, focusing on channel migration, width variation, sinuosity, meander curvature, and sediment budget changes. Using multi-temporal satellite data and geospatial analysis, key indicators were quantified across 41 cross-sectional zones to evaluate morphodynamic responses over four time intervals: 1987–1975, 1999–1987, 2011–1999, and 2023–2011. Results show a progressive intensification of lateral channel migration, with several zones recording annual rates exceeding 4 m/year and R² values above 0.90. Channel width increased significantly, from a mean of 4.75 m to 83.64 m, confirmed by repeated measures ANOVA (p < 0.001). Although the sinuosity index did not change significantly (p = 0.223), localized trends indicated both meander amplification and channel straightening. The Radius-to-Width ratio remained consistently above 2.0, suggesting morphological stability in bend curvature. Sediment analysis revealed a shift from net erosion (–181.55 m²) in 1987–1975 to substantial net accretion (+ 2778.11 m²) by 2023–2011, with a strong linear trend (R² = 0.90). These morphodynamic changes are linked to climate variability, extreme floods, and anthropogenic pressures such as land use change and riverbank modification. The findings highlight the need for integrated, data-driven river management approaches to mitigate flood risks and guide sustainable development in riverine environments.