Impacts of frozen layer and rock fragment on sediment transport capacity on frozen‐stony slopes

Abstract

AbstractCold areas commonly experienced freeze–thaw cycles and covered with rock fragment. Exploring sediment transport capacity of frozen‐stony soil scoured by concentrated meltwater flow is meaningful for soil erosion prediction and modelling in cold regions. This laboratory experiment is conducted to evaluate the contribution of frozen layer and rock fragment to soil erosion, which involves three slope gradients of 5°, 10°, and 15°, three flow rates of 1, 2, and 4 L min−1, four thawed soil depths of 1, 2, 5, and 10 cm, and four rock fragment contents of 0%, 10%, 20%, and 50% on mass basis with rill length of 12 m. Sediment concentration was determined by the soil in runoff at the outlet. An equation is proposed to estimate sediment transport capacity affected by thawed soil depth and rock fragment content by combining exponential and quadratic functions. Model‐fitting results show that sediment transport capacity is negatively correlated with thawed soil depth and exhibits quadratic relationship with rock fragment which peaks at 20% and significantly decreases at rock fragment of 50% on partially thawed slope. Rock fragment takes the leading role of soil erosion on frozen‐stony slope instead of thawed soil depth. Results also indicate that embedded rock fragment on totally thawed soil presents more apparently positive impact at low content, but offers more protection at high content on partially frozen layer. This research reveals the soil erosion mechanisms on frozen‐stony slope and gives guidance for soil conservation in similar hydrologic conditions and soil type.