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ARS Home » Southeast Area » Oxford, Mississippi » National Sedimentation Laboratory » Watershed Physical Processes Research » Research » Publications at this Location » Publication #196631
Title: Simulating Ephemeral Gully Erosion in AnnAGNPS

Author
item GORDON, LEE - UNIVERSITY AT BUFFALO
item BENNETT, SEAN - UNIVERSITY AT BUFFALO
item Bingner, Ronald - Ron
item THEURER, FRED - USDA, NRCS
item Alonso, Carlos

Submitted to: Transactions of the ASABE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/15/2007
Publication Date: 6/1/2007
Citation: Gordon, L., Bennett, S.J., Bingner, R.L., Theurer, F., Alonso, C.V. 2007. Simulating Ephemeral Gully Erosion in AnnAGNPS. Transactions of the ASABE, Vol. 50(3): 857-866.

Interpretive Summary: Ephemeral gullies serve as effective links transferring sediment and associated agrichemicals from upland areas to stream channels. Current erosion prediction technologies often require the exact topographic location of an ephemeral gully to be known, which greatly limits the application of such models. Technology has been developed in this study that incorporates state-of-the-art ephemeral gully science within watershed models. This includes the scour that is produced below ephemeral gully headcuts and the rate that the headcuts move up into the agricultural fields after rainfall events. Sediment that is eroded within the ephemeral gully is routed downstream within fields where the watershed model integrates all other sediment sources within a field, such as from sheet and rill erosion, and then combined with any other contributions including from channels to move the sediment to the watershed outlet. Ephemeral gully processes included within a watershed model also provides a tool that can determine the effect of conservation management practices and changing soil conditions on the development ephemeral gully erosion. This technology allows a more accurate and physically based examination of sediment sources in agricultural watersheds, providing tools necessary to effectively manage the Nation’s water and soil resources.

Technical Abstract: Ephemeral gullies serve as a major source and transport mechanism of sediment and associated agrichemicals from upland areas. Accurate prediction technology is necessary to assess the magnitude of these phenomena and to identify areas where mitigation measures are critical. Current ephemeral gully prediction technologies require the exact topographic position (the length) of an ephemeral gully a priori, which greatly limits the utility of such models. The Revised Ephemeral Gully Erosion Model has been developed as a rational approach to predict ephemeral gully erosion and development and to overcome limitations of previous ephemeral gully prediction tools. While REGEM functions as a stand alone tool, it has been developed for integration as an additional module within the Annualized Agricultural Non-Point Source (AnnAGNPS) suite of watershed modeling tools developed by the USDA. REGEM incorporates analytic formulations for plunge pool erosion and headcut retreat within single or multiple storm events in unsteady, spatially-varied flow at the sub-cell scale. The model addresses five soil particle-size classes to predict gully evolution and transport capacity. The governing equations for the model are presented and discussed and single event and continuous simulations demonstrate the model’s utility for predicting both the initial development of an ephemeral gully and its evolution over multiple runoff events, accounting for seasonal variations in management operations and soil conditions. A comparison to field conditions is made in which REGEM is shown to recreate dimensions of measured ephemeral gullies.