Sanders Maryn A, Roering Joshua J, Burns William J, Calhoun Nancy A, Leshchinsky Ben A
Department of Earth Sciences, University of Oregon, Eugene, OR 97403, USA.
Oregon Department of Geology and Mineral Industries, Portland, OR 97232, USA.
Sci Adv. 2025 Aug 8;11(32):eadw8633. doi: 10.1126/sciadv.adw8633.
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 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- to 10-year) erosion from debris fans and volcanic edifice reconstruction. Fan-derived 10-year erosion rates (1 to 9 mm year) exceed 10-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-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.
大量泥石流扇从俄勒冈州哥伦比亚河峡谷（CRG）陡峭的集水区流出，该地区因晚更新世大洪水而地貌巨变。2017年，鹰溪大火烧毁了CRG的200公里区域，引发了对泥石流活动加剧的担忧，但其对潜在危险的影响仍不明确。为评估火灾对CRG的10个集水区的影响，我们利用机载激光雷达、图像和实地观测，以及泥石流扇的长期（10至10年）侵蚀和火山 edifices重建，对火灾前后的泥石流侵蚀进行了量化。源自扇体的10年侵蚀率（1至9毫米/年）比10年侵蚀率高出10至50倍，这表明大洪水后这些集水区持续快速解体。火灾前后的泥石流侵蚀率与10年侵蚀率一致，因此火灾导致的侵蚀在大洪水后的剥蚀中占比相对较小（<10%），这意味着CRG地区存在持续的地貌不平衡，表现为无论野火情况如何，都具有持续的高潜在危险。
