Large Igneous Provinces (LIPs) have been implicated in some of the largest environmental perturbations to have affected the Earth through geological time. Yet the impact of LIP development on drainage and ecosystem development in the immediate vicinity of these provinces are still poorly constrained to date. Based on a detailed, integrative facies scheme we characterize the interaction between volcanism and fluvial, lacustrine, and wetland environments in the Miocene Columbia River Flood Basalt Province (CRBP) LIP exposed in central Washington State, USA. The facies scheme proposed here comprises a detailed description and interpretation of siliciclastic, bioclastic (diatomite), volcaniclastic, and paleosol facies and subfacies intercalated with lavas of the Columbia River Basalt Group (CRBG). Facies and facies associations of individual interbeds are further correlated to reconstruct changes in sedimentary settings and topography of lava fields during deposition. Field observations and facies analysis help to explain the effects of flood-basalt volcanism on drainage-system development. We propose a generic model of lava–drainage interplay and distribution of sedimentary settings in flood-basalt provinces, which will contribute to our understanding of sedimentological, environmental, and volcanic processes in the CRBP. Hydrocarbon exploration in volcanic terrains requires detailed information on the distribution and development of sedimentary settings. This model will help to better predict the character and distribution of sedimentary bodies and potential hydrocarbon reservoirs in volcanic terrains.