Post-Fire LiDAR Change Detection, 2017 Eagle Creek Fire, Columbia River Gorge, Oregon

With increasing wildfire activity in the western USA, understanding the role this process plays in the geomorphic evolution of landscapes is becoming more significant. In September 2017, the Eagle Creek fire in Oregon burned through nearly 50,000 acres of steep vegetated landscape along the Columbia River Gorge. The incineration of vegetation can destabilize colluvium on steep slopes and alter hydraulic properties causing landscapes to become more prone to highly destructive debris flows, rapid soil erosion, and rock falls. The Eagle Creek fire provides a natural laboratory to compare pre- and post-fire LiDAR data to assess how slope angle, soil burn severity, tree-coverage, and lithology influence post-fire erosion patters of a landscape of forested area underlain by basalt flows. The National Center for Airborne Laser Mapping (NCALM) collected a new LiDAR data set over the burn area in May 2018 that we compare using raster and point-cloud based DEMs of difference (DoDs) with pre-fire LiDAR data sets (2005, 2009, 2010, and 2014) collected by the Oregon Lidar Consortium (OLC) and the U.S. Army Corp of Engineers (USACE). From these analyses we calculate the spatial pattern of post-fire erosion and deposition to quantify rockfalls and dry ravel and their contribution of sediment to channels and valley networks. Using basalt flow properties, hillslope morphology, and vegetation maps, we can characterize controls on post-fire erosion. By estimating the volume of post-fire erosion, we can determine the fractional contribution of long-term erosion that occurs in post-fire episodes. This work will better inform land management and ecological function in these landscapes given predictions of increased fire frequency due to climate change.