Extreme events such as floods threaten infrastructure, lives, and livelihoods, as well as altering landscapes and ecosystems. Climate change is increasing the frequency of such events and heightening the imperative to understand their drivers and landscape responses and to translate such understanding into hazards reduction. In mid-June 2022, extreme floods on the Yellowstone River and many of its tributaries in and around northern Yellowstone National Park were generated by an atmospheric river that delivered 2.5–10 cm of rain to high-elevation snowpack. Large rain-on-snow floods have created large and persistent channel changes in Yellowstone in the past, and they may become more common in a warming climate. The extreme June 2022 event provides a rare opportunity to examine its magnitude and effects on Yellowstone River tributaries. This project will support research experiences for five undergraduate students and one M.S. student and represents a new collaboration between primarily undergraduate-serving and very high research activity institutions. The project will contribute to National Park Service after-event analysis and planning. The investigators will engage broad audiences through social media. Project findings will be incorporated into university classes.<br/><br/>This research aims to reconstruct flood hydraulics and assess the hydrogeomorphic effects of the June 2022 event, to contextualize the impacts relative to previous extreme flooding events, and to inform geohazards planning at Yellowstone National Park. These goals will be accomplished by targeted field surveys, geomorphic change analysis over larger areas using repeat lidar, and hydraulic modeling. The investigators' efforts will focus on areas that are both well-suited to the research questions and have pre-flood data. Research objectives include estimating the hydraulics of the June 2022 flood and how the flood affected channel geometry and floodplain character, including incision and/or aggradation of Yellowstone River tributaries. The research is time sensitive and urgent because landscape changes induced by the floods are most evident in the immediate aftermath, before subsequent rainfall events in 2022 and the spring 2023 snowmelt runoff season further rework fluvial systems and floodplains. Further, rapid deployment will allow the team to contribute to National Park Service after-event analysis and planning.<br/><br/>This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.