USDA Forest Service

Pacific Southwest Research Station

 
Pacific Southwest
Research Station

800 Buchanan Street
Albany, CA 94710-0011
(510) 883-8830
United States Department of Agriculture Forest Service. USDA logo which links to the department's national site. Forest Service logo which links to the agency's national site.

Estimates of Surface and Mass Erosion Following the 2016 Emerald Wildfire

Principal Investigators:
William Elliot, USDA Forest Service, Rocky Mountain Research Station
Longxi Cao, State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences
Jonathan Long, USDA Forest Service, Pacific Southwest Research Station
Mariana Dobre, University of Idaho
Roger Lew, Michigan Technological Research Institute
Mary Ellen Miller, USDA Forest Service-Rocky Mountain Research Station

Proposal [pdf]

Final Report [pdf]

Workshop on Road Sedimentation Processes in the Lake Tahoe Basin, September 18, 2018:
Agenda [pdf]
Presentation from 2018 Stakeholder Meeting [pdf]

Additional Reports:
Brooks et al. 2017

Project Summary

In 2016, the Emerald Fire burned 70 ha (173 acres) near the southwest corner of Lake Tahoe on the ridge between Cascade Lake and Tallac Creek. The occurrence of this fire in an area with two roads and a LIDAR elevation data set provided an opportunity to evaluate the impacts of roads on post wildfire erosion, and to test other postfire erosion modeling tools. This study evaluated road effects on soil erosion in a fire-disturbed forest with GIS technology and a soil erosion model, and the likelihood of mass failure by debris flow, translational failure and dry ravel.

Results showed that roads could alter flow paths and reroute sediment transport, leading to deposition and reducing soil loss in a fire disturbed forest. WEPP-predicted sediment deposition on road surfaces and in sediment basins was similar to observed deposition. The predicted likelihood of a debris flow occurring was about 35 percent, and no debris flows have been observed. There is, however, a high likelihood of a translational landslide occurring within 4 to 6 years as the roots of the dead trees decompose. The dry ravel results suggest that there is a risk of some deposition on Highway 89 due to dry ravel until sufficient vegetation is reestablished to stabilize some of the steeper slopes.