Bio-engineered StreamBank Stabilization Using Wetland Sod on the Teton River: A Case Study

Abstract

Wetland sod in combination with erosion control fabric was used to re- construct and stabilize an eroding streambank on the Teton River in southeast Idaho. The river has an average base flow of 5.67 m 3 /s and an average peak flow of 34 m 3 /s. Above and throughout the study area the Teton River is a predominantly ground water fed, free flowing system with a moderate spring run- off. Conditions at the study site pre-construction included an average bank height of 1.07 m, an average bank slope of 2:1 and dominant bank vegetation consisting of introduced pasture grasses. The dominant soil type was a silty clay loam. The existing bank was reconstructed by first excavating the bank down to the base- flow water line to a width of 3.66 m. Two layers of long-term erosion control fabric were staked onto the base of the excavated bank using 20 cm wire staples. Soil was compacted onto the erosion control fabric layers to a depth of 0.30 m. Approximately 1 m of the erosion control fabric was wrapped up onto the compacted soil to build the initial toe of reconstructed bank. The remaining soil was sloped back to create a bank with an average slope of 3:1. Wetland sod, a pre-vegetated coir product planted with native sedges and rushes, was installed in two rows onto the constructed toe and remaining bank to a width of 1.83 m. A total of 77 m of eroding bank was reconstructed in 2 days at a cost of $195 per linear meter. In 1 month post construction the pre-vegetated coir material was fully rooted and could not be displaced by human or animal disturbance.