Quantifying the Impact of Model Selection When Examining Bank Retreat and Sediment Transport in Stream Restoration

Abstract

The objective of this study was to assess the performance of form-based and process-based models, and of local-scale and reach-scale models, used to examine bank retreat and sediment transport in stream restoration. The evaluated models were the Bank Erosion Hazard Index (BEHI), Bank Assessment for Nonpoint Source Consequences of Sediment (BANCS), Bank Stability and Toe Erosion Model (BSTEM), and HEC River Analysis System (HEC-RAS 1D). Model-to-model assessments were conducted to quantify the impact of model selection when predicting applied stress and geomorphic change in a restored stream in North Carolina, USA. Results indicated that the mobility of the bed dictated model selection at the reach-scale. The process-based HEC-RAS 1D was needed to accurately analyze the sand-bed stream, predicting amounts of geomorphic change comparable to measured data and up to three orders of magnitude higher than those from local-scale models. At the local-scale, results indicated that the bank retreat mechanism and flow variability constrained model selection. The form-based BEHI and BANCS did not directly account for geotechnical failure nor capture severe floods, underpredicting amounts of geomorphic change by an order of magnitude when compared to the process-based BSTEM, and failing to characterize erosion potential and applied stresses after short-term morphodynamic adjustments.