DOWNSTREAM IMPACT AND CHANNEL RESPONSE TO POST-FIRE HILLSLOPE PROCESSES

The hillslope processes that shape the mountainous terrain of the Pacific Northwest have contributed significant changes to the region’s river systems. In September 2017, a large wildfire on the Columbia River Gorge burned approximately 200 km² of forested mountain terrain cradling Eagle Creek, a tributary to the Columbia River. Since the fire, Eagle Creek has begun the process of recovery. However, there is still missing evidence of the changes the fire has had on the landscape, especially within the stream channel itself. Previous post-fire research has found that the characteristics and parameters of hillslope processes are altered by wildfire but expected to return over time, however stream process responses are less understood. This study looks to quantify the changes and downstream impacts these processes have had on Eagle Creek following the fire. Performing repeat terrestrial lidar scans (TLS) after peak storm events will create a time series of bedload movement over the course of the study. Results from TLS will allow me to produce a rate of bedload transport using a hydraulic distribution model (Yanites, 2018) that was delivered to the channel through processes of localized shallow landslides, bank failure and active channel incision. This project seeks to better understand the long-term effects that wildfires have on fluvial systems with the goal of identifying the geomorphic response towards recovery within the stream channel. As climate change is expected to increase wildfire occurrence, the results of the study will have implications for future post-fire research.