Network-Scale Patterns of Valley Confinement and Widening in the Oregon Coast Range

Valley floor morphology in mountain landscapes reflects an integrated history of fluvial incision, lateral erosion, and aggradation in uplifting terrain. Valley floor width is often modeled as a power-law with catchment area. Yet these models often report high variance across the entire domain and low R-squared values. Valley floor width commonly varies even within individual mountain catchments, with multiple transitions between confined segments and wider alluvial reaches. Characterizing this spatial variability enables better understanding of valley widening processes and helps identify reaches with floodplain restoration potential. In this project we develop a network-scale method to quantify valley floor morphology and apply it to the river networks of the Oregon Coast Range. The approach automates mapping of valley floor extents and measures widths at increasing inundation levels scaled from bankfull depth. We examine how these widths vary along networks and test whether there are differences in patterns of confinement and widening based on lithology, geomorphic history, and network position. Our results represent a step forward in interpreting the types and sources of variability in valley floor geometry beyond drainage-area scaling.