دانلود رایگان مقاله انگلیسی تخمین قابلیت فرسایش خاک منظره با استفاده از رویکرد GIS در اتیوپی شمالی - الزویر 2017

abstract

Soil erosion is a very critical form of land degradation resulting in the loss of soil nutrients and downstream sedimentation of water storages in the highlands of Ethiopia. As it is technically and financially impossible to conserve all landscapes affected by erosion, identification of priority areas of intervention is necessary. Spatially distributed erosion models can help map landscape susceptibility to erosion and identify high erosion risk areas. Integration of erosion models with geographic information systems (GIS) enables assessing evaluate the spatial variability of soil erosion and plan implementing conservation measures at landscape levels. In this study, the Revised Universal Soil Loss Equation adjusted for sediment delivery ratio was used in a GIS system to assess landscape sensitivity to erosion and identify hotspots. The approach was applied in three catchments with size being 10–20 km2 and results were compared against quantitative and semi-quantitative data. The model estimated mean soil loss rates of about 45 t ha
1 y
1 with an average variability of 30% between catchments. The estimated soil loss rate is above the tolerable limit of 10 t ha
1 y
1 . The model predicted high soil loss rates at steep slopes and shoulder positions as well as along gullies. The results of the study demonstrate that knowledge of spatial patterns of high soil loss risk areas can help deploy site-specific conservation measures.

4. Conclusion

This study demonstrates that spatially distributed models that do not require extensive data can be applied to provide a reasonable guide for identifying conservation priority areas. The Revised Universal Soil Loss Equation model adjusted for complex terrain applied in this study showed that the rate of soil erosion in most of the studied catchments is above the rate that can be tolerated. The model adequately identifies areas of high sediment yield which need to be prioritized for management intervention. Based on the rates and spatial patterns of soil loss, it can be generalized that reservoirs located at the confluence of collapsing gullies upslope will experience high siltation risk and thus need to be conserved before constructing dams. Such simplified information should be of great value to decision makers and planners in pinpointing locations where intervention is necessary to reduce soil loss from catchments and its delivery into reservoirs. However, it generally appears that the model over predicts soil loss on areas of complex topography, which means that its performance could vary for different sites highlighting that there is no single model that can be applicable to different sites with diversified attributes. It is thus necessary to calibrate and validate before applying models to evaluate their applicability to the environmental conditions of areas under consideration.