Morphometric Analysis of the West Rapti River Basin: Geospatial Assessment and Hydrological Implications

Background and aim of the study: The West Rapti River Basin in Nepal is a crucial geographical region with significant ecological and socio-economic importance. Planning for sustainable development, evaluating the danger of flooding, and managing land and water resources effectively all depend on an understanding of this basin's morphometric features. This work performs a thorough morphometric examination of the West Rapti River Basin using GIS methodologies. Data and Methodology: The analysis incorporates various morphometric parameters, including linear, areal, and relief aspects, to assess the basin's geometric and topographic properties. The study utilizes remote sensing data, Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) digital elevation models (DEMs), and geographic information system (GIS) tools to extract relevant morphometric attributes. Results: It was discovered that the river basin had a dendritic structure, with an uneven tendency in SLR flowing from the youth to the mature stage. Its shape was less elongated, and its southern portion had more runoff. Quantitative methods based on compound ranking of each attribute and land use land cover (LULC) based on possible erosion risk have been tried to prioritize 25 sub-watersheds (SW). A mean composite score inculcating parameters and LULC was computed ranging from 6 to 16.5. The findings revealed that SW3, SW5, SW8, SW9, and SW12 were very highly prioritized sub-watersheds whereas SW13, SW15, SW21, SW23, and SW24 were found to be in very low category. The analysis of five year data of the river basin demonstrated that the river course has changed over the time affecting 17.6 sq. km. area to erosion and 15. 2 sq. km. area to accretion mostly at the river’s syntaxial bends and southern parts of the watersheds. Conclusion: This research contributes to the scientific understanding of river basin morphology and provides valuable information for sustainable land and water resource management. Different watershed management treatment to prevent soil erosion can be performed on priority basis which prevent further degradation of critically eroded area.