Prioritisation of soil erosion-prone sub-watersheds for river health restoration in the Budhabalanga basin through PCA–WSA and morphometric analysis: a geo-spatial technology approach

Abstract

Soil erosion within upstream sub-watersheds is a key contributor to sedimentation, channel instability and water quality degradation in fluvial ecosystems. The identification of erosion prone sub-watersheds, therefore, forms a prerequisite for the successful restoration of river health and watershed management. This investigation prioritises sixteen sub-watersheds of Budhabalanga River using morphometric parameters clubbed with Principal Component Analysis (PCA) and Weighted Sum Analysis (WSA). Eighteen morphometric descriptors were computed from a 30-meter resolution Digital Elevation Model (DEM) using ArcGIS software. PCA was used to identify the important erosion controlling variables while WSA was utilised to calculate a compound factor (CF) that forms the basis of the final prioritisation. PCA results showed that five variables, i.e. relief ratio, elongation ratio, rho coefficient, stream frequency and drainage density, account for more than 92.546% of the total variance. On the basis of the CF, three sub-watersheds were classified as very high priority and an additional three as high priority thus including approx. 1/3 of the basin area. These priority zones represent potential areas of elevated erosion and sediment-generation susceptibility and therefore warrant targeted investigation and conservation measures for reducing sediment delivery to downstream reaches. Here, the PCA-WSA integration objectively identifies erosion hotspots and guides targeted river restoration.