The influence of wildfire on debris flows in a landscape of persistent disequilibrium: Columbia River Gorge, OR, USA.
Where this comes from
- Record sourced from PubMed, PMID 40779633.
- Also identified by DOI 10.1126/sciadv.adw8633 and PMC identifier 12333674.
- Licence recorded as CC BY-NC.
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Abstract
Extensive debris flow fans emanate from steep catchments in the Columbia River Gorge (CRG), Oregon, a landscape dramatically reshaped by Late Pleistocene megafloods. In 2017, the Eagle Creek Fire burned 200 km<sup>2</sup> of the CRG, prompting concerns of heightened debris flow activity, yet its impact on hazard potential remains unclear. To assess the fire's effect on 10 CRG catchments, we quantify pre- and postfire debris flow erosion using airborne lidar, imagery, and field observations, as well as long-term (10<sup>4</sup>- to 10<sup>6</sup>-year) erosion from debris fans and volcanic edifice reconstruction. Fan-derived 10<sup>4</sup>-year erosion rates (1 to 9 mm year<sup>-1</sup>) exceed 10<sup>6</sup>-year rates by 10 to 50 times, suggesting sustained, rapid unraveling of these catchments following the megafloods. Pre- and postfire debris flow erosion rates are consistent with 10<sup>4</sup>-year rates, such that fire-derived erosion accounts for a relatively small fraction of post-megaflood denudation (<10%), implying persistent landscape disequilibrium that manifests as ongoing high hazard potential in the CRG, regardless of wildfire conditions.