Effect of Soil Water Content on Soil Detachment Capacity for Coarse‐ and Fine‐Grained Soils

Abstract

Core Ideas Aging had a nonlinear effect on soil detachment capacity for fine‐grained soil. Detachment capacity of fine soil had a concave pattern as soil water increased. Detachment capacity of coarse soil had a convex pattern as soil water increased. A systematic set of flume tests was developed to explore the relation between soil water content and soil detachment capacity for a coarse‐grained soil and a fine‐grained soil. The experiments included aging treatments (three volumetric water contents of 4.0, 11.5, and 21.7% for the sandy loam soil and 5.0, 10.5, and 17.4% for the silt loam soil, and seven aging durations of 0, 12, 24, 36, 48, 60, and 72 h) and drying treatments (saturated soil samples oven‐dried for 0, 12, 24, 36, 48, 60, and 72 h). Results showed that soil detachment capacity for these two soils presented unique patterns as soil water content increased: the fine‐grained soil presented an increasing and then a decreasing trend under aging treatments, whereas the coarse‐grained soil showed a continuous increasing trend as soil water content increased. Both patterns could be fitted by quadratic equations. The effect of soil water content on soil detachment capacity was mainly reflected by water‐stable aggregate content. Higher soil water content results in weaker bonds for fine‐grained soil but in less slaking for coarse‐grained soil. Lower soil water content leads to less slaking for fine‐grained soil but more particle deposition and cementation for coarse‐grained soil. Future work will include additional soil textures and focus on soil erodibility and critical shear stress to expand our understanding of soil detachment influenced by soil water content.

Saturation effect on the distribution of rill detachment rate

“…Thus, the soil strength of saturated soil is considerably weakened compared with that of non‐saturated soil (Auerswald, Muchler, & Mcgregor, 1994; Rudoloph, Helming, & Diestel, 1997). Moreover, the soil saturation state may make the critical shear stress decrease and soil erodibility increase (Liu, Wells, Dabney, & He, 2017; Zhang, Li, Wells, & Liu, 2019). Greater amounts of saturated soil were detached compared with non‐saturated soil under similar slope gradient and flow rate.…”

“…Greater amounts of saturated soil were detached compared with non‐saturated soil under similar slope gradient and flow rate. In addition, critical shear stress is possibly increased and soil erodibility is increased under the saturated condition, which could cause rapid erosion (Bertolino et al, 2010; Liu et al, 2017; Zhang et al, 2019). The second aspect is that soil saturation reduces the energy consumption of soil detachment.…”