Erosion hotspot identification in the sub-humid Ethiopian Highlands
Abstract
Soil degradation and associated soil erosion is a daunting challenge for small holder farmers of the Ethiopian Highlands. Identifying and mapping erosion hotspots can help to set priority areas for soil conservation interventions. While remotely sensed data and GIS techniques are found to be important in generating vital quantitative information on soil erosion, studies indicated that this method alone fails to properly account for important hydrological processes driving erosion. Moreover, most erosion modeling studies lack representation of critical catchment sediment sources such as gullies, which leads to under prediction of soil loss. In this study, remote sensing data and the Revised Universal Soil Loss Equation (RUSLE) were coupled with multi criteria landscape analysis to map erosion hotspot areas in the Upper Gilgel Abbay watershed of the sub-humid Ethiopian highlands. The results of the classic RUSLE model indicated that annual average soil loss of the study area was up to 288 t/ha. In the majority (83%) of the area the predicted soil loss was between 0-40 t/ha; 13% soil loss was between 40-100 t/ha and in the remaining 4% areas soil loss was in excess of 100 t/ha. Spatially, the classic RUSLE predicted higher erosion rates for the uplands and lower erosion for the bottomlands. However, our field gully mapping and our studies in the sub-humid Ethiopian highlands indicated that most gullies, which are critical sources of catchment sediment yields, are associated with saturated bottomland areas. The location of bottomland gullies also coincided with important hydrologic parameters such as higher Soil Wetness and Stream Power Index values. The implication is that in addition to RUSLE, criteria such as gullies, land use, soil wetness index and stream power index values should be used in erosion risk mapping studies in environments where soil saturation plays an important role in gully formation and expansion.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.H22I..03M
- Keywords:
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- 1807 Climate impacts;
- HYDROLOGYDE: 1807 Climate impacts;
- HYDROLOGYDE: 1813 Eco-hydrology;
- HYDROLOGYDE: 1813 Eco-hydrology;
- HYDROLOGYDE: 1815 Erosion;
- HYDROLOGYDE: 1815 Erosion;
- HYDROLOGYDE: 1843 Land/atmosphere interactions;
- HYDROLOGYDE: 1843 Land/atmosphere interactions;
- HYDROLOGY