Location: Watershed Management ResearchTitle: Advances in modeling soil erosion after disturbance on rangelands Author
|Al-hamdan, Osama - Texas A&M University|
|Williams, Christopher - Jason|
|Boll, Jan - Washington State University|
|Nouwakpo, Sayjro - University Of Nevada|
|Spaeth, Kenneth - Natural Resources Conservation Service (NRCS, USDA)|
Submitted to: World Conference Soil and Water Conservation Under Global Change (CONSOWA)
Publication Type: Proceedings
Publication Acceptance Date: 4/1/2017
Publication Date: 6/16/2017
Citation: Al-Hamdan, O., Pierson Jr, F.B., Nearing, M.A., Williams, C.J., Hernandez Narvaez, M.N., Boll, J., Nouwakpo, S., Weltz, M.A., Spaeth, K. 2017. Advances in modeling soil erosion after disturbance on rangelands. Proceedings of World Conference Soil and Water Conservation Under Global Change (CONSOWA). p. 422-425.
Technical Abstract: Research has been undertaken to develop process based models that predict soil erosion rate after disturbance on rangelands. In these models soil detachment is predicted as a combination of multiple erosion processes, rain splash and thin sheet flow (splash and sheet) detachment and concentrated flow detachment. Knowing soil erodibility associated with each process is a key factor for achieving satisfied performance of such models. We present advancement in developing equations to predict erodibility on disturbed rangeland. Two different approaches were developed for erodibility estimation on degraded sites. These approaches were conceptualized based on observations and results of experimental studies on rangelands. In the first approach, where concentrated flow detachment is negligible, only the splash and sheet erodibility parameter is needed to predict erosion due to disturbance. The approach uses empirical equations that were developed by applying piecewise regression analysis to predict the differences of splash and sheet erodibility before and after disturbance and across a wide range of soil textures as a function of vegetation cover and surface slope. The breakpoint generated by the piecewise regression identifies a threshold at which there is a substantial change in the rate of erodibility increase with respect to bare soil area, and therefore provides an objective means for detecting changes between natural and disturbance phases. In the second approach, concentrated flow erodibility is also calculated to predict soil erosion due to disturbance. This approach is used in the case of abrupt disturbance that exposes loose sediments on a steep slope. The approach uses empirical equations that were developed by applying regression analysis to predict the differences of concentrated flow erodibility before and after disturbance as a function of vegetation cover and soil texture. It also uses empirical function to predict temporal erodibility variation within a runoff event as a function of cumulative flow. The two erodibility estimation approaches were tested using the Rangeland Hydrology and Erosion Model (RHEM) and showed satisfactory results in predicting impact of disturbance on erosion.