Near-Bank Impacts of River Stage Control

Abstract

Retention of pools to allow navigation has produced a characteristic, anomalous topography on a number of rivers (e.g., Ohio, Illinois, Kanawha). A gently sloping subaqueous bench at and just below minimum pool stage has been observed at hundreds of sites on these rivers. Bench formation is 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. The shallow-water zones over these benches are ecologically significant. Design and construction of bank protection measures must address the mechanisms that produce these benches.