Geomorphological analysis of the Gelda sub-watershed for hydrological and watershed management, Tana Sub-basin, Ethiopia

Abstract

Investigating the geomorphological and hydrological characteristics of a watershed is essential for determining and predicting erosion potential, controlling runoff, and developing conservation strategies for land and water resources. However, such quantitative assessments were limited in the Gelda Sub-watershed. The objective of this study was to assess the morphometric characteristics of the entire Gelda Sub-Watershed, enabling the prediction of erosion potential and the identification of priorities for implementing conservation practices. For delineating the 26 sub-watershed and compute the significant morphometric parameters that directly related the hydrological and erosional response of the watershed counting bifurcation ratio, drainage density, basin relief, relief ratio, dissection index, ruggedness number, infiltration number length of over land flow and stream frequency a 12.5 m by 12.5 m resolution Digital Elevation Model (DEM) and ArcGIS 10.7 were used. For prioritizing the most vulnerable sub-watersheds via erosion, and suggesting appropriate erosion management strategies, the Composite Parameter Factor (CPF) value was employed. The results indicate that sub-watersheds, including WS-19, WS-23, WS-20, WS-22, WS-25, and WS-26, with CPF values ranging from 8.00 to 9.44, were highly vulnerable to erosion and classified as very high-priority areas requiring immediate conservation measures. High-priority areas such as WS-14, WS-2, WS-16, and WS-10 necessity appropriate intervention, whereas Medium and low-priority sub-watersheds accounting for 33.75% of the study area require moderate maintenance-level measures. Overall, 57.98% of the sub-watershed falls within very high and high priority classes, which need abrupt soil and water conservation measures like terracing, check dams, afforestation, and land-use regulation. The finding may contribute to practical applications in targeted and cost-effective soil and water preservation measures, support sustainable watershed management, boost agricultural production, and strengthen landscape resilience against degradation. Moreover, it reveals that the combined technique of morphometric analysis, combined with field verification, offers a strong and reproducible framework for sub-watershed prioritization. This approach facilitates efficient watershed management and can be extended to other Ethiopian basins and other similar landscapes to assist erosion control, enhance groundwater recharge, and encourage sustainable terrestrial management. Clinical trial number: The manuscript titled Geomorphological Analysis of Sub-Watershed for Enhancing Hydrological Assessment and Sustainable Watershed Management: A Case Study of Gelda Watershed, Tana Sub-Basin, Ethiopia, does not include a Clinical Trial Number.