Erosion landscape characterization in the Himalayan basin: insights from geospatial data and multi-criteria evaluation

In regions characterized by mountainous landscapes, such as watersheds with high elevations, steep inclines, and rugged terrains, there exists an inherent susceptibility to water-induced soil erosion. This susceptibility underscores the importance of identifying areas prone to erosion to mitigate the loss of valuable natural resources and ensure their preservation over time. In response to this need, the current research employed a combination of four multi-criteria decision-making (MCDM) models, namely TOPSIS-AHP, VIKOR-AHP, ARAS-AHP, and CODAS-AHP, for the identification of areas susceptible to soil erosion within the Himalayan River basin of Nandakini, Uttarakhand, India. This identification was facilitated through the utilization of remote sensing and geospatial technologies. The study considered a total of 19 prioritization parameters that included morphological, topo-hydrological, climatic, and environmental factors specific to the Nandakini catchment for the purpose of prioritization modeling. The adoption of morphometric parameters in depicting the geological structures and hydrodynamic behavior of the river basin proves to be a crucial approach in locales where hydrological data may be scarce. The investigation delineated twenty watersheds within the catchment by employing SRTM DEM, SOI toposheets, and Geographic Information Systems (GIS), calculating the catchment's total area to be approximately 540.98 km². The analysis determined that the catchment is classified as a 6th-order catchment, exhibiting mainly a sub-dendritic to dendritic drainage pattern. It was identified that the catchment is vulnerable to flooding and subsequent gully erosion due to the slow movement of surface runoff. Furthermore, the catchment's elongated shape and the compactness coefficient suggest a delayed peak runoff. The drainage texture ranged from very coarse to coarse, and the relief characteristics highlighted that the watersheds within the catchment possess a high relief ratio, thereby increasing their erosion vulnerability. Topo-hydrological indices revealed significant topographic variability and spatial differences in water availability and erosion potential across the basin. The efficacy of the MCDM models was evaluated through the Spearman's correlation coefficient test, alongside indices of intensity and percentage of change, to validate the findings. The ARAS-AHP and CODAS-AHP models were found to exhibit superior efficiency and higher accuracy relative to the other methods assessed. The insights gained from the ARAS-AHP and CODAS-AHP models are instrumental in the development of strategies for sustainable catchment management plans and inform decision-making processes regarding water resources management within the catchment.