|Bingner, Ronald - Ron|
Submitted to: International Symposium on Gully Erosion
Publication Type: Proceedings
Publication Acceptance Date: 6/25/2007
Publication Date: 9/17/2007
Citation: Bingner, R.L., Theurer, F.D., Gordon, L.M., Bennett, S.J., Parker, C., Thorne, C., Alonso, C.V. 2007. AnnAGNPS Ephemeral Gully Erosion Simulation Technology. Proceedings of the IV International Symposium on Gully Erosion. September 17-19, 2007, Pamplona, Spain, J. Casali and R. Gimenez (eds). Public University of Navarre. p. 20-21, 2007. Interpretive Summary: The National Resources Inventory (NRI), conducted by the U.S. Department of Agriculture’s Natural Resources Conservation Service (NRCS), in cooperation with Iowa State University’s Center for Survey Statistics and Methodology, reported that there has been a 42% decrease in sheet and rill erosion in the U.S. between 1982 and 2003. 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 combined topographic analysis techniques to locate ephemeral gullies within a watershed with enhancements to watershed models to simulate ephemeral gully processes that then provides opportunities to assess the impact of conservation practices on ephemeral gully erosion as well as sheet and rill 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.
Technical Abstract: Sheet and rill erosion conservation management technologies, such as the Revised Universal Soil Loss Equation (RUSLE), have provided valuable tools in reducing cropland erosion, but have not considered the impact of ephemeral gully erosion. Tillage-induced ephemeral gully erosion has been shown to be a significant and sometimes dominant source of sediment within a watershed. U.S. Department of Agriculture’s Natural Resources Conservation Service (NRCS) has requested improvements in USDA Agricultural Research Service (ARS) technologies to account for watershed sources of sediment from ephemeral gully erosion through the USDA Annualized Agricultural Non-Point Source model (AnnAGNPS). AnnAGNPS has been developed to determine the effects of conservation management plans and provide sediment tracking from all sources within the watershed, but did not previously include ephemeral gully components. Technology is also needed to identify where ephemeral gullies may form in the watershed using geographic information system (GIS) technology. These technologies have been developed within AnnAGNPS to assess the impact of conservation practices on ephemeral gully erosion as well as sheet and rill erosion. By defining where ephemeral gullies are through GIS techniques and when management operations would occur that disturbs the soil, the model can simulate the formation and growth of ephemeral gullies throughout the watershed. By tracking the source of sediments, conservation management practices can be targeted specifically for ephemeral gully erosion that can be different than for sheet and rill erosion. A comparison with field studies is shown for sites in Kansas and Ohio.