Seepage-Induced Streambank Erosion and Instability: In Situ Constant-Head Experiments

Abstract

The effects of seepage on streambank erosion and failure are less understood compared to fluvial processes, especially the linkage between surface water and groundwater mechanisms. Field data are needed to validate laboratory seepage erosion and instability conclusions and to understand how engineering tools and methods may be applied to field conditions. An innovative trench injection system was utilized to provide a constant head on a near-streambank groundwater system when filled with stream water. This research was performed on a streambank of Dry Creek, a deeply incised stream with near-vertical banks located in Mississippi. Experiments included installing a trench (2.8 m from the bank and 2 m below ground surface) and a network of tensiometers and observation wells to measure soil-water pressures and water table elevations. Bank stratigraphy consisted of a sloping, conductive loamy sand layer between cohesive streambank layers. Groundwater conditions were monitored during a series of induced-seepage experiments. The bank face was outfitted with a seepage collection device to measure seep flow rates and sediment concentrations. Seepage flow rates (as high as