Near-Bank Impacts of River Stage Control

A gently sloping subaqueous bench is the topographical phenomenon resulting from the retention of pools to allow navigation in controlled-stage streams. Bench formation has been observed at many sites on the Ohio, Illinois, and Kanawha Rivers. They are the result of bank failure and erosion processes including seepage-induced erosion, localized failure of undermined layers, reworking of failed soils by waves, and erosion by current forces. Benches are prevalent along alluvial banks composed of layered soils and are covered by a shallow water zone that is ecologically significant. This article summarizes the research to date on the bench phenomenon and draws inferences for future work in bank protection and development of riverine ecosystems.