Valley confinement is the degree to which topographic features, such as hillslopes, alluvial fans, glacial moraines, and river terraces, limit the lateral extent of the valley floor and the floodplain along a river. Unconfined valleys are generally less extensive than confined valleys in montane environments, but host a diverse array of terrestrial and aquatic organisms and provide disproportionately important ecosystem functions (e.g., hyporheic exchange, pool-riffle channel morphology, suitable grain sizes for spawning, riparian habitat). Confined valley bottoms exhibit different geomorphic features and thus serve different roles in the landscape.
Nagel, David E.; Buffington, John M.; Parkes, Sharon L.; Wenger, Seth; Goode, Jaime R. 2014. A landscape scale valley confinement algorithm: Delineating unconfined valley bottoms for geomorphic, aquatic, and riparian applications. Gen. Tech. Rep. RMRS-GTR- 321. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station. 42 p.