302-4 Wildfire and River Restoration: Assessing Potential Impacts and Risks to Projects

Abstract:

River restoration activities are growing in number, size, and complexity at the same time as wildfires are growing in number, size, and intensity. Fire and river restoration are not inherently at odds, however. When collocated, fire can directly burn project elements (wood and vegetation) and indirectly enhance or detract from projects via increased runoff, debris flows, sediment loading, and wood loading. Functioning river corridors can act as fire breaks, provide refuge, and attenuate runoff, sediment, and wood, but context such as river corridor width, pre-fire fuel loading, and fire intensity can influence local outcomes. It is important to consider the potential direct and indirect impacts of wildfire and the risk of the impacts occurring during the early stages of restoration planning in (recently) unburned watersheds. With support and leadership from the U.S. Bureau of Reclamation, we developed a GIS-based methodology using existing wildfire hazard and other national datasets that characterize the susceptibility of a site to increased debris flows, wood loading, sediment loading, and altered runoff conditions. Our goal is to help practitioners assess potential risks to a project if wildfire was to occur at the site or in its contributing basin. We applied the methodology to three case study sites in Oregon and Washington: Phipps Meadow, Lookingglass Creek, and the Chiwawa River. Phipps Meadow has a low overall risk of potential wildfire-related response. Both Lookingglass Creek and the Chiwawa River have varied risks of potential wildfire-related responses, ranging from low to high. These results and feedback compiled from project partners indicate that the methodology provides quality planning-level data prior to a wildfire occurring in a watershed. The methodology does not, however, consider site-specific routing of fire-related impacts, and therefore watershed-specific knowledge must be employed to interpret the results. The outputs should not be used to prioritize site selection and should instead be used for planning once a site has been chosen. Since the methodology makes use of publicly-available national datasets, we encourage practitioners to use it to assess the potential impacts of wildfire in watersheds slated for restoration anywhere in the United States. Future work will compare the outputs of the methodology with the actual observed effects of the 2026 wildfire season on restoration projects in the Pacific Northwest.

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