Pacific Southwest Research Station

Erosion of Fine Sediment from Roads

The Forest Service Lake Tahoe basin Management Unit has used the WEPP: Road modeling tool to evaluate road decommissioning and best management practices (BMP) upgrades. For WEPP: Road to produce more accurate results, the model parameters need to be refined for the Tahoe basin.  Additionally, the WEPP: Road model interface has not been able to simulate erosion along roads with armored/rocked fillslopes and non-forested buffers adjacent to stream channels. By making these refinements, the model will help to understand and identify nonpoint pollution sources and to select and evaluate BMPs.

Full title: Improving road erosion modeling for the Lake Tahoe basin and evaluating BMP strategies for fine sediment reduction at watershed scales

Proposal [pdf-192KB]

Lead Researchers: Randy B. Foltz and William Elliot, USDA–FS Rocky Mountain Research Station; Woodam Chung, University of Montana; Hakjun Rhee, Washington State University

Goals

1. Parameterize the WEPP model for the Lake Tahoe basin with simulated rainfall experiment data from the road running surface.
2. Validate the WEPP model against field observation data for both paved and unpaved roads.
3. Improve WEPP: Road interface to:
   1. Change fillslope and buffer material type and cover.
   2. Model crowned and entrenched roads.
   3. Model cutslope erosion.
4. Develop a GIS-based quantitative approach to:
   1. Predict the sediment loading using WEPP: Road
   2. Identify erosional “hot spots” from a watershed-scale road network.
   3. Determine the optimal road network design that minimizes sediment production through BMP application and road decommissioning.

Sites: Twelve square meter plots within the basin on decomposed granite and volcanic ash, four road segments monitored for runoff, and GIS modeling of roads throughout the basin