Evaluation of the Conservational Channel Evolution and Pollutant Transport System (CONCEPTS) Applied to Composite Streambanks in the Ozark Highlands Ecoregion

Abstract

<abstract> <bold>Abstract.</bold> Hydraulic models are often employed to predict the response of a stream to a proposed restoration design. The shortfall of many currently used models is that they only look at the site where stabilization will occur without considering upstream and downstream effects. The one-dimensional (1D) computer model Conservational Channel Evolution and Pollutant Transport System (CONCEPTS) addresses this shortcoming by modeling streambank stabilization on a reach scale. The capability of this model is attractive to basin managers; however, CONCEPTS is still an emerging model and has not been applied to a wide variety of composite streambanks. The objectives of this study were to perform an evaluation of the Conservational Channel Evolution and Pollutant Transport System (CONCEPTS) applied to composite streambanks in the Ozark Highlands ecoregion, and to demonstrate CONCEPTS’s ability to predict the long-term stability of streambank stabilization. CONCEPTS was used to simulate a 9.25 km reach along the Barren Fork Creek in northeastern Oklahoma. A sensitivity analysis was first performed to identify input parameters with the greatest effect on bank erosion predictions in CONCEPTS. Model results were most sensitive to (1) the correction factor that accounts for increased shear stresses in a meandering stream that cannot be simulated by 1D models and (2) the internal angle of friction of the bank soils followed by the critical shear stress, effective cohesion, erodibility coefficient and the permeability. Next, CONCEPTS was calibrated using ground-based and aerial bank retreat measurements to produce realistic predictions. Model calibration was conducted by reducing the critical shear stress of the noncohesive soils until the predicted retreat matched the observed data. Using the calibrated model, two streambank stabilization techniques were simulated at two highly unstable cross sections. Fluvial erosion was reduced by simulating the application of riprap at the bank toe, and geotechnical failure was reduced by simulating a slope stabilization technique. In general, CONCEPTS predicted a high percent reduction of cumulative fines yield, bank retreat at the bank top and toe, and cumulative change in thalweg elevation for both stabilization techniques. Due to CONCEPTS limitations, a two or three-dimensional model may be needed to perform a comprehensive analysis of streambank stability for the composite streambanks in the Ozark Highlands ecoregion. Additional research is needed on the use of the internal angle of friction as a lumped calibration parameter for cohesionless soils. However, with the proper calibration and caution, CONCEPTS is a useful tool to guide the design and prioritization of streambank stabilization projects.