Soil Moisture Impacts Linear and Nonlinear Erodibility Parameters from Jet Erosion Tests

Abstract

HighlightsThe jet erosion test (JET) remains the most commonly used instrument for measuring in situ erodibility.This research investigated the impact of soil moisture content below saturation on erodibility parameters.Erodibility parameters were derived for both linear and nonlinear detachment models.Higher soil moisture increased initial resistance to erosion but also increased erosion rate.Abstract. The jet erosion test (JET) is a commonly employed technique to measure the erodibility of soils in situ by estimating the parameters of linear and nonlinear cohesive sediment detachment models. However, additional research is needed to understand the effect of soil moisture, a critical in situ test condition, on the derived erodibility parameters. This study compared the erodibility parameters, i.e., critical shear stress (tc) and the erodibility coefficient (kd) for the linear excess shear stress equation and two parameters (b0 and b1) for a nonlinear detachment model, from laboratory JETs across two soil types with contrasting texture and moisture contents. The general pattern was that higher soil moisture content increased the soil’s initial resistance to erosion (i.e., higher tc and b1), but once erosion was initiated the rate of erosion was greater (i.e., higher kd and b0). The magnitude of the changes in the erodibility parameters across the three soil moisture profiles investigated in this research were statistically significant, with kd and b0 varying by as much as a factor of 3. This research also confirmed the greater impact of soil moisture content on kd and b0 as compared to tc and b1. For the range of shear stress applied during these JETs, a linear detachment model was more appropriate for the sandy loam soil but less so for the more cohesive clay loam soil, but results were limited to a narrow range in applied shear stress. The results further support existing research conclusions that in situ erodibility measurements obtained under one set of soil moisture conditions may need to be adjusted to better predict soil detachment during storm events. Keywords: Cohesive soil, Critical shear stress, Detachment model, Erodibility, Jet erosion test, Shear stress, Soil moisture.