| dc.description.abstract | The process of soil loss includes the removal of soil material from one location via natural erosive agents or human-induced agents and their deposition to another location. It results in reduced soil fertility, water quality, and reservoir capacity. Mountainous watersheds exhibit complex topography and diverse features, characterized by steep slopes, deep valleys, and high peaks, which significantly influence hydrological processes and water distribution. As a result, modeling and mapping soil loss presents considerable problems in these areas. A combined approach of different soil loss models that account for various soil loss processes can enhance soil loss modeling in these areas. The purpose of this study is to assess soil loss in the Manafwa watershed using the RUSLE 3D and USPED models. Five factors were considered as input model parameters: rainfall erosivity derived from mean annual rainfall data obtained from the CRU data website, soil erodibility extracted from the NARO soil dataset, topographic factors (LS) derived from a 30m resolution DEM downloaded from the USGS website, cover management obtained from NDVI calculations using Landsat 8 imagery's band 4 and band 5, and conservation practices. The resulting maps were resampled to match the 30m resolution of the DEM and Landsat 8 imagery before being fed into the models to calculate soil loss. The performance of the models was evaluated by comparing them to run off plots ground data. The RUSLE 3D soil loss rates varied from 0 to 24.67 t ha−1yr−1, classified into four categories: extremely low (0 –1 t ha−1 year−1), low (1 – 5 t ha−1 year−1), medium (5 – 10 t ha−1 year−1), high (10 – 20 t ha−1 year−1), and extremely high (>50 t ha−1 year−1). To understand the spatial patterns of soil loss, soil loss rates per district within the watershed were determined. The results showed that Bududa had the highest soil loss, followed by Namisindwa, Mbale, Manafwa, and Butaleja with the least soil loss. Similarly, the USPED soil loss rates varied from -66.83 to 66.79 t ha−1yr−1, categorized into six classes: high soil loss (< -5 t ha−1 year−1), moderate soil loss (-5 – -1 t ha−1 year−1), low soil loss (-1 – -0.1 t ha−1 year−1), stable (-0.1 – 0.1 t ha−1 year−1), low deposition (0.1 – 1 t ha−1 year−1), moderate deposition (1 – 5 t ha−1 year−1) and extreme deposition( > 5 t ha−1 year−1). The negative values indicated soil loss while the positive values indicated deposition. Analyzing soil loss per district within the watershed revealed that Bududa, Namisindwa, and Mbale experienced more soil loss and deposition, while Manafwa and Butaleja showed more deposition than soil loss. The findings of this study highlight the importance of focusing conservation efforts on steep slopes and areas near stream networks, which were identified as hotspots for soil loss. | en_US |
