Evaluating watershed erosion through hypsometric analysis with remote sensing and GIS: a case of gelda watershed, Tana Sub-Basin, Ethiopia

Understanding the status of watershed erosion is essential for effective watershed management and sustainable water resources utilization. This study aimed to determine the erosion vulnerability of the Gelda entire watershed and its 26 sub-watersheds within the Tana sub-basin, Ethiopia, using hypsometric analysis. The data analysis began processing a 12.5 m by 12.5 m digital elevation model (DEM) in ArcGIS 10.5 to delineate 26 sub-watersheds from WS-1 to WS-26 and extract the DEM of each of the watersheds. Subsequently, the hypsometric curve and integral (HI) were computed for the entire Gelda watershed and its 26 sub-watersheds. The result indicates the entire watershed has an HI of 0.49, which is a mature stage, and the sub-watersheds range from 0.4 for WS-7 to .51 for WS-5 and WS-21, revealing varying degrees of erosion vulnerability. The watershed with higher HI values correlated with a youthful, erosion-prone landscape, whereas the sub-watershed (WS-7) with an HI value of 0.4 revealed that this sub-watershed is a relatively more mature and stable landscape. The coefficient of determination (R2) exceeds 0.5, confirming the robustness of the hypsometric curves in accurately representing topographic features. This is aligned with a similar study conducted by Raja Shekar (Watershed Ecol Environ 6:13–25, 2024). The study highlights the practical application of hypsometric analysis for regional watershed erosion conservation. It enables prioritizing the soil conservation measures, including tracing and check dams in high erosion watersheds like WS-5 and WS-21, and encourages groundwater recharge mechanisms for watersheds like WS-7. Moreover, this study provides essential information for planning and implementing targeted interventions such as afforestation in stable zones and structural erosion control measures in susceptible areas. These are critical in reducing erosion risks and enhancing sustainable land use planning within the Gelda watersheds. This study offers an essential outline for generating appropriate information in similar data scarcity basins and offers insights into basin dynamics and efficient management, emphasizing the necessity of targeted investments to mitigate erosion and maintain ecological balance.