ERODIBILITY PARAMETERS DERIVED FROM JET EROSION TESTS ON ROOT-PERMEATED SOILS

Jet erosion tests (JETs) allow for the process-based quantification of erodibility parameters of cohesive soils. The critical shear stress (τ_c) corresponds to the stress at which fluvial forces can detach soil particles or aggregates and the erodibility coefficient (k_d) governs how fast detachment occurs when the imposed fluvial shear exceeds τ_c. This research hypothesized that if JETs are performed on soils permeated with shallow root systems of riparian grass species and therefore have exposed roots around the scour hole, then the surrounding soil will have a shallower equilibrium scour depth, a higher τ_c, and a lower k_d. JETs performed on root-permeated soils had a significantly higher τ_c but insignificant differences in k_d compared to JETs on adjacent bare soil. There was a correlation between exposed root surface area and k_d but no correlation between exposed root surface area and τ_c or the equilibrium scour depth. Based on these findings and for these conditions, above-ground biomass may play a more significant role than root networks in lessening fluvial erosion.