Linking post-fire stream responses to watershed characteristics across the Pacific Northwest

Wildfire can have dramatic effects on stream ecosystems. These changes may be beneficial or detrimental to human uses of streams. The inherent variability in watershed controls on stream properties can complicate efforts to generalize the net effects of wildfire on stream ecosystems. We have developed a watershed classification with the express goal of characterizing and leveraging variability in post-fire responses of aquatic systems. The classification approach assigns all sub-catchments in Oregon, Washington, and Idaho to a biophysical sensitivity class. The assignments are made using more than 350 biophysical watershed-scale metrics. In addition to the biophysical classification, watersheds are further stratified according to their burn characteristics. Burned watersheds from each biophysical class were then compared to a regional dataset of compiled stream quality measurements to quantify hypothesized variability in watershed responses. This spatially explicit classification is intended to provide a useful tool for tailoring post-fire interventions and monitoring approaches for assessing intervention efficacy. Additionally, by explicitly accounting for nuances in watershed-level drivers of stream response to wildfire, this framework should enable improved flexibility in the decision-making process facing those tasked with overseeing post-fire recovery.

Impact/Purpose

Wildfires, and their effects on human property, watersheds, and ecosystem values are a growing concern in the Western US. Wildfires and associated responses can negatively affect water quality through increased loadings of sediment, introduction of toxic chemicals, and changes to how water is stored and routed through watersheds. But wildfires can also help create conditions that provide long-term benefits to aquatic ecosystem condition, by creating stream habitats that support desired functions for fish, wildlife, and water quality. In this poster we will present a classification approach for characterizing differing ways in which wildfires can influence water quality and aquatic habitat. This research is part of a larger effort intended to help managers identify best practices for protecting and restoring aquatic habitats and water quality.

Citation

Almquist, V., J. Ebersole, R. Hill, AND M. Beyene. Linking post-fire stream responses to watershed characteristics across the Pacific Northwest. American Fisheries Society Annual Meeting, Reno, NV, September 29 - October 03, 2019.