People have congregated along the Columbia River's banks throughout history, from the earliest settlements to contemporary metropolises, but this close proximity has posed a serious threat when extreme flooding occurs. Understanding how climate change will affect the future flood risk throughout the Columbia River Basin is imperative for risk mitigation and infrastructural planning. To address this question, we analyze an ensemble data set which provides daily streamflow values (1950-2100) for 172 different future projections for 396 locations in the Columbia River Basin. The ensemble members were created with a modeling decision chain which included two representative concentration pathways, ten global climate models, two meteorological downscaling methods, and four hydrological model setups. From the daily timestep streamflow data, we use extreme events from each water year to estimate flood flow values for floods with 10-, 20- and 30-year return periods. From this analysis, we find a substantive increase in flood risk for all simulated stream gauge locations in the Columbia River Basin. Our results emphasize how the hydrologic response to climate change at an streamflow location is intrinsically region and watershed dependent. Sites along the Columbia and Willamette Rivers are estimated to have a higher increase in flood-risk the further downstream the site is located. Sites along the Snake River, however, are estimated to have a lower increase in flood-risk the further downstream the site is located.