Development and Testing of a Physically Based Model of Streambank Erosion for Coupling with a Basin-Scale Hydrologic Model SWAT

Abstract

A comprehensive streambank erosion model based on excess shear stress has been developed and incorporated in the hydrological model Soil and Water Assessment Tool (SWAT). It takes into account processes such as weathering, vegetative cover, and channel meanders to adjust critical and effective stresses while estimating bank erosion. The streambank erosion model was tested for performance in the Cedar Creek watershed in north-central Texas where streambank erosion rates are high. A Rapid Geomorphic field assessment (RAP-M) of the Cedar Creek watershed was done adopting techniques developed by the Natural Resources Conservation Service (NRCS), and the stream segments were categorized into various severity classes. Based on the RAP-M field assessment, erosion pin sites were established at seven locations within the severely eroding streambanks of the watershed. A Monte Carlo simulation was carried out to assess the sensitivity of different parameters that control streambank erosion such as critical shear stress, erodibility, weathering depth, and weathering duration. The sensitive parameters were adjusted and the model was calibrated based on the bank erosion severity category identified by the RAP-M field assessment. The average observed erosion rates were in the range 25-367 mm year−1. The SWAT model was able to reasonably predict the bank erosion rates within the range of variability observed in the field (R2 = 0.90; E = 0.78). Editor's note: This paper is part of the featured series on SWAT Applications for Emerging Hydrologic and Water Quality Challenges. See the February 2017 issue for the introduction and background to the series.