State Water Resources Research Institute Program


Project ID: 2012WA353B
Title: Progress towards assessing the large-scale impacts of forest fires on runoff erosion across the Pacific Northwest
Project Type: Research
Start Date: 3/01/2012
End Date: 2/28/2013
Congressional District: Washington5
Focus Categories: Hydrology, Sediments, Climatological Processes
Keywords: erosion modeling fires
Principal Investigators: Adam, Jennifer (Washington State University); Adam, Jennifer (Washington State University)
Federal Funds: $ 27,000
Non-Federal Matching Funds: $ 54,048
Abstract: In the western U.S., there is clear concern for increases in wildfire occurrence and severity due to projected climate changes. For example, degradation of water quality occurs in post-fire periods due to water erosion of bare soils. Water erosion is important because excess sediment in streams continues to be a concern for resource managers across the United States. Statistics compiled by the U.S. EPA in 1996 and 1998 indicated that 24% of surface water impairment involved sediments, suspended solids, or turbidity. Excess sediment adversely impacts aquatic life, navigation, reservoir sedimentation and flood storage, drinking water supply, and aesthetics. In the Pacific Northwest region, researchers have shown that agricultural production is a primary source of fine sediments, but continued research by these and other researchers have also found that forest wildfires likely provide a large percent of the coarser sands that settle in navigation channels and in reservoirs.

Our long-term goal is to quantify the adverse water-quality impacts due to extreme wildfires and associated runoff erosion under projected climatic changes across the western U.S. The overarching goal for this particular proposal is to advance our capability to simulate post-fire runoff erosion at scales larger than a single hillslope, in order to examine the relative contribution of sediment being released to larger streams and rivers in response to wildfire. We propose to apply a newly-developed physically-based modeling framework that combines large-scale hydrology with hillslope-scale runoff erosion. The modeling system will first be tested and evaluated at two field sites in the region where our U.S. Forest Service (USFS) collaborators have collected post-fire erosion data. Secondly, the model will be implemented over a larger watershed, the Salmon River basin (SRB), as a proof of concept for large-scale post-fire erosion modeling. Finally, we will perform scenario simulations to examine the relative sensitivity of SRB erosion rates to climate versus land cover and soil parameterizations, particularly as they relate to extreme wildfires. This proposed project is unique because it is the first study (that we are aware of) to use physically-based models to examine the very large (i.e., regional) scale impacts of extreme wildfires on erosion processes.

This project will fund one MS student in engineering and will result in a masters thesis and one publication in the near term, with many potential publications to follow. Results will be presented at conferences and, in the long term, will be disseminated to forest managers in the region through our USFS collaborators. GIS maps will be produced that can be used to visualize the spatial distribution of erosion rates within the CRB as well as the relative sensitivity of these erosion rates to climate, land cover, and soil characteristics. This project relates directly to SWWRC priority activity #1, "climate change effects on water balances, stream flows, and water quality".

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