INTEGRATED ASSESSMENT AND ANALYSIS OF PHYSICAL LANDSCAPE PROCESSES THAT IMPACT THE QUALITY AND MANAGEMENT OF AGRICULTURAL WATERSHEDS
Location: Watershed Physical Processes Research Unit
Title: Simulating Ephemeral Gully Erosion in AnnAGNPS
| Gordon, Lee - UNIVERSITY OF BUFFALO |
| Bennett, Sean - UNIVERSITY OF BUFFALO |
| Theurer, Fred - NRCS |
| Alonso, Carlos |
Submitted to: Transactions of the ASABE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 15, 2007
Publication Date: June 1, 2007
Citation: Gordon, L.M., Bennett, S.J., Bingner, R.L., Theurer, F.D., Alonso, C.V. 2007. Simulating Ephemeral Gully Erosion in AnnAGNPS. Transactions of the American Society of Agricultural & Biological Engineers International, Vol. 59(3): 857-866.
Interpretive Summary: Erosion control practices within agricultural watersheds have a significant impact on reducing the sheet and rill source of sediment to the streams. While these practices have significantly affected sheet and rill erosion, they do not appreciably affect ephemeral gully erosion. Ephemeral gully erosion is becoming a dominate source of cropland erosion simply because sheet and rill erosion is decreasing. Current ephemeral gully erosion technology available for assessment of ephemeral gully erosion within watersheds is very limited, empirically-based, and applicable to only the field scale. This study contributed significant ephemeral gully modeling enhancements to an ARS watershed model that then provides opportunities to assess the impact of conservation practices on ephemeral gully erosion. This information can be used in the development of improved watershed conservation management plans by Federal action agencies, such as NRCS, EPA, and the US Army Corps of Engineers.
Ephemeral gully erosion can cause severe soil degradation and contribute significantly to total soil losses in agricultural areas. Physically-based prediction technology is necessary to assess the magnitude of these phenomena so that appropriate conservation measures can be implemented, but such technology currently does not exist. To address this issue, a conceptual and numerical framework is presented where ephemeral gully development, growth, and associated soil losses are simulated within the Annualized Agricultural Non-Point Source (AnnAGNPS) model. This approach 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, and addresses five soil particle-size classes to predict gully evolution, transport-capacity and transport-limited flows, gully widening, and gully reactivation. 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. The model is shown to recreate reasonably well the dimensions of observed ephemeral gullies in Mississippi. The inclusion of ephemeral gully erosion within AnnAGNPS will greatly enhance the model’s predictive capabilities and further assist practitioners in the management of agricultural watersheds.