Modeling root effects on soil detachment capacity using critical flow depth and unit energy of cross section in soils under Fraxinus excelsior L. species

The flow depth is an important hydraulic parameter for calculating other hydraulic parameters of overland flow. There is notable changes in hydraulic parameter when the roots of a plant develop in the topsoil. A power regression equation between soil detachment capacity (D_c) and unit energy of cross section (UEC) was established in soils under Fraxinus excelsior L. species based on the Froude number. For measuring D_c, samples collected from soils under the studied species and subjected to five slopes (from 13.9 to 33.9%) and five water discharges (from 0.39 to 0.77 L m⁻¹ s⁻¹) by a hydraulic flume. Compared with the soil with absence of root, the soil with presence of root had lower D_c. The results showed a strong power relationship between the unit energy of cross section and D_c, suggesting that soil detachment rate in rill erosion can be estimated using this hydraulic parameter (R² = 0.84). This finding is particularly relevant for hillslopes with slopes from 12% to 31%, where the proposed mathematical model could be applied to predict D_c. Overall, this investigation supports a broader use of native species (such as the european ash Fraxinus excelsior L.), as a useful eco-engineering conservation practice and an alternative technique instead of utilizing artificial and expensive conservation practices.