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United States Department of Agriculture

Agricultural Research Service

Research Project: Assessment, Conservation and Management of Rangelands in Transition

Location: Northwest Watershed Management Research

Title: Modeling soil erosion impact of rangeland disturbance using the Rangeland Hydrology and Erosion Model (RHEM)

Authors
item Al-Hamdan, Osama -
item Pierson, Frederick
item Nearing, Mark
item Hernandez, Mariano -
item Stone, Jeffry
item Williams, Christopher
item Boll, Jan -
item Weltz, Mark

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: July 17, 2013
Publication Date: July 21, 2013
Citation: Williams, C.J., Pierson, F.B., Spaeth, K.E., Al-Hamdan, O.Z., Weltz, M.A., and Boll, J. 2013. Eco-hydrology considerations for enhancement of ecological site descriptions [abstract]. Soil and Water Conservation Society 68th International Annual Conference, Resilient Landscapes: Planning for Food, Drought, and Fire, July 21-24, 2013 Reno, Nevada.

Technical Abstract: Disturbance on rangeland such as fire and tree encroachment can increase overland flow erosion rate by increasing the likelihood of concentrated flow formation on a more erodible surface. In this study, we made advancements to RHEM by developing a new version of the model to predict concentrated flow erosion from disturbed rangelands. The model was conceptualized based on results from experimental studies conducted by the USDA-ARS Northwest Watershed Research Center on rangelands disturbed by fire and/or by tree encroachment. The major concepts of the model are: 1) Probability of overland flow to become concentrated increases with increasing slope angle, percentage bare soil, and flow discharge per unit width; 2) Concentrated flow soil erodibility changes within a runoff event where it has a maximum value at the beginning of the event and then decreases exponentially due to the reduction in sediment availability; 3) Soil erodibility of a site can be predicted by readily available ground cover and soil texture data; 4) Stream power is the driver that causes concentrated flow soil detachment, where soil detachment initiates once concentrated flow forms (i.e. no threshold concept for initiating detachment); 5) Width of concentrated flow path increases with increasing flow discharge and decreasing slope. The new approach utilizes empirical equations developed from experimental studies on disturbed rangelands to provide the parameters needed to run the model. The modified RHEM was evaluated on a plot scale (32.5 m2) using data obtained from rainfall simulation experiments on two sites, where one was disturbed by fire and the other was disturbed by tree encroachment. We believe that this modified version of RHEM expands the applicability of the model and will provide a tool to assist land managers in making decisions by predicting the potential hydrologic and erosion impacts of tree removal, prescribed fire, and other conservation practices and disturbances.

Last Modified: 12/26/2014
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