Relationships between physical‐geochemical soil properties and erodibility of streambanks among different physiographic provinces of Tennessee, USA

Abstract

AbstractErosion of cohesive soils in fluvial environments is dependent on physical, geochemical and biological properties, which govern inter‐particle attraction forces and control detachment rates from stream beds and banks. Most erosion rate models are based on the excess shear stress equation where the soil erodibility coefficient (kd) is multiplied by the difference between the boundary hydraulic shear stress (τb) and the soil critical shear stress (τc). Both kd and τc are a function of soil properties and must be obtained through in situ field or laboratory testing. Many studies have generated predictive relationships for kd and τc derived from various soil properties. These studies typically were conducted in watersheds within a single physiographic region with a common surficial geology and/or investigated a limited number of soil properties, particularly geochemical properties. With widely reported differences in relationships between τc and soil properties, this study investigated differences in predictive relationships for τc among different physiographic provinces in Tennessee, USA. Erodibility parameters were determined in the field using a mini‐jet test device. Among these provinces, statistically four unique clusters were identified from a dataset of 128 observations and these data clusters were used to develop predictive models for τc to identify dominant properties governing erosion. In these clusters, 16 significant physical and geochemical soil properties were identified for τc prediction. Among these soil properties, water content and passing #200 sieve (percentage soil less than 75 μm) were the dominant controlling parameters to predict τc in addition to clay percentage (< 2 μm), bulk density, and soil pore water chemistry. This study suggests that unique relationships exist for physiographic provinces that are likely due to soil physical‐geochemical processes associated with surficial geology that determine minerology of the cohesive soil. Copyright © 2017 John Wiley & Sons, Ltd.