The project will investigate the impacts of large, rare geologic events, such as landslides or lava flows, on the evolution of bedrock river valleys in the semi-arid, uplifted volcanic plateaus of the interior Columbia River basin. These events are termed "extrafluvial" because they are initiated outside of the river channel itself, but alter the river by changing the channel slope and width; burying the valley bottom; or creating temporary dams that can generate cataclysmic floods upon failure. We hypothesize that these periodic channel-encroaching events are a dominant force in creating and maintaining the geomorphic features of many river canyons. The Owyhee River in southeastern Oregon is the principal field site in which the individual and combined impacts of these catastrophic events will be explored. Geospatial analyses will be used to map and understand the distribution of these processes on other rivers in the region. From these results, reach-scale calculations of incision potential will be made to address quantitatively the relations between landslide/lava invasions and river channel evolution. The results will contribute to the rapidly expanding field of landscape modeling by improving representations of the processes by which rivers carve their valleys.
Broader Impacts Central Washington University (CWU) and Lewis and Clark College (LCC) are primarily undergraduate institutions; students will conduct the geospatial analysis in an undergraduate course, participate in field trips through the College Outdoors Program, and work directly with investigators. The Science Talent Expansion Program at CWU, partially targeted at students from underrepresented groups in science, will be a source for recruiting participants. Close collaborations with scientists at the U.S. Geological Survey and U.S Forest Service will help disseminate results to stakeholders. The project will contribute to an understanding of geologic hazards posed by large landslide dams and has implications for assessing river-channel impacts of removing human-constructed dams.
