Dalmo A. N. Vieira

The application of the Revised Universal Soil Loss Equation, Version 2, to evaluate the impacts of alternative climate change scenarios on runoff and sediment yield

The Revised Universal Soil Loss Equation, Version 2 (RUSLE2), provides robust estimates of average annual sheet and rill erosion for one-dimensional hillslope representations. Extensive databases describing climate, soils, and management options have been developed and are widely used in the United States for conservation planning. Recent RUSLE2 enhancements allow estimation of erosion and runoff from a representative sequence of runoff events that are suitable for linkage with an ephemeral gully model. This paper reviews the sensitivity of RUSLE2 erosion estimates to possible climate change scenarios, demonstrates its ability to evaluate alternative management adaptations, and compares predictions with observations of runoff and sediment yield from a 6.6 ha (16 ac) research watershed located near Treynor, Iowa. When applied to a representative hillslope profile with conventional tillage corn (Zea mays L.), increasing monthly temperature by 0.8°C (1.5°F) and rainfall depth, rainfall erosivity density, and 10-year, 24-hour rainfall depth each by 10% cumulatively increased sheet and rill erosion by 47% and increased runoff by 33%, assuming there was no change in corn yield. If the climate changes decreased corn yield by 10%, the overall effect was to increase soil loss for conservation planning by 63%. These results demonstrate that modest and expected changes in climate will significantly increase the risk of soil erosion, and improved conservation management will be an important part of successful adaptation.

Effects of Topographic Feedback on Erosion and Deposition Prediction

Soil erosion and depositional processes result in changes in topographic and soil profile properties over time. In spite of this, few current soil erosion models account for these changes. To begin to address this deficiency, a distributed version of RUSLE2 has been developed and used in combination with the tillage erosion model TELEM (Vieira and Dabney, 2010). These models were applied to a 6.6 ha research watershed near Treynor, IA, where runoff and sediment yield were measured on a daily basis from 1975 through 2002. The watershed contained a grassed waterway and, beginning in 1991, ~1-m wide grass hedges were established with 15.4 m interval between the grass hedges. Beginning in 1996, no-till management replaced conventional tillage management in the watershed.