Comment on hess-2021-399

The soil erosion of the spoil tips seriously threatens the safety of people's lives and property and the surrounding ecological environment. Rill erosion is an important cause of water and soil loss in spoil tips. This study was conducted to investigate the process of rill erosion on the slopes of spoil tips, changes in the morphological characteristics of rills and the mechanisms of rill erosion. A Field runoff plot (5 m long, 1 m wide and 0.5 m deep) with three inflow rates (1.6, 2 and 2.4 mm min−1) and three typical slopes (28°, 32° and 36°) was used for runoff simulation experiments. The results showed that, compared with the slope and scouring times, inflow rate was the most important factor affecting rill erosion of the spoil tips. The development of rill mainly goes through three stages: the rill formation stage, the rill development stage and the rill adjustment stage. The overall predominance of parallel-shaped rills at all experiments suggested that the formation of rills was dominated by concentrated runoff. The average rill depth was the best indicator of rill morphology for evaluating rill erosion. The flow regimes under the experimental conditions were supercritical-laminar flow and supercritical-transition flow. The Reynolds number was the best hydraulic parameter for predicting rill erosion. The stream power was the best hydrodynamic parameter to describe rill erosion mechanism. These results contributed to further revealing the rill erosion mechanism on the slope of the spoil tips and provided a scientific basis for its soil erosion control.

Runoff scouring experimental study of rill erosion of spoil tips

Impacts of rainfall and inflow on rill formation and erosion processes on steep hillslopes

Characterizing erosion processes on a convex slope based on 3D reconstruction method

Core Ideas Effects of inflow rate on the Mollisol erosion process were examined. Inflow rate effects on soil loss were dependent on the dominant erosion pattern. When upslope inflow was included, soil loss increased 12 to 1950 times. Different hydrodynamic parameters were crucial for sheet and rill erosion. Inflow water from upslope is an extremely important factor that influences downslope erosion processes. Little information is available concerning how inflow water affects downslope erosion processes in the Chinese Mollisol region, where a large amount of runoff is generated from upslope. The purpose of this study was to determine the effects of inflow rate on erosion processes and flow hydrodynamic parameters. A soil pan (10 m long, 1.5 m wide, and 0.5 m deep) was subjected to rainfall simulation and inflow experiments under one rainfall intensity (50 mm h −1 ), two slope gradients (5 and 10°), and five inflow rates (50, 100, 150, 200, and 300 L min −1 ). The result showed that when upslope inflow was included, soil loss increased 12 to 1950 times compared with no upslope inflow. When rill erosion dominated, rill erosion accounted for 52 to 90% of the total soil loss as the inflow rate increased from 50 to 300 L min −1 . An increase in the inflow rate from 50 to 300 L min −1 caused the flow velocity to increase 0.6 to 7.8 and 1.7 to 12.9 times at 5 and 10° slopes, respectively, while the Darcy–Weisbach coefficient decreased from 13.5 to 95.4%. For sheet‐dominated erosion, significant linear regressions were fitted between shear stress, stream power, unit stream power, and inflow rate; but for rill‐dominated erosion, power functions were established between these flow hydrodynamic parameters and the inflow rate.

Evaluating the effects of forest tree species on rill detachment capacity in a semi-arid environment

Apportioning contributions of individual rill erosion processes and their interactions on loessial hillslopes

Extensive areas in the Valley of Mexico are covered by highly erodible volcanic soils.The traditional methods of managing these soils with deep ripping and cultivation haveincreased soil erosion. Soil erosion is greatly influenced by the interactions between rainfall andsoil characteristics and therefore, the study of interrill and rill erosion can be very helpful indeveloping new approaches for controlling soil erosion in order to maintain sustainableproduction and environmental integrity. The objective of this study was to evaluate the effect ofgypsum on interrill erosion and the effect of polyacrylamide on rill erosion in a highly erodiblevolcanic soil from the Valley of Mexico using rainfall and runoff simulation techniques. In theinterrill area, surface application of gypsum increased infiltration and reduced runoff, soil erosionand surface sealing. Rill erosion caused by concentrated flow was practically reduced to zerowhen polyacrylamide (PAM) was applied in simulated rills. The use of soil amendments tocontrol soil erosion appears to be a viable management method for reclaiming highly erodiblevolcanic soils at a lower cost.

THE National Resource Inventories (NRI) carried out by the Soil Conservation Service in 1977 provide statistical data on sheet and rill erosion for all nonfederal land in the United States (excluding Alaska) and data on wind erosion in 10 Great Plain States. The data were ob-tained by visiting plots and randomly selected points to gather information for use in the Universal Soil Loss Equation and Wind Erosion Equation models. The NRI show that soil lost by sheet and rill erosion annually amounts to 3.5 billion metric tons (t). About one-half of this loss is from the 167-million-ha cropland base; the most sloping 26 percent contributes 79 percent of the cropland erosion. In 19 states and the Caribbean Area, estimated average annual cropland sheet and rill erosion exceeds 11.2 t/ha. In four states and the Caribbean Area the rate exceeds 22.4 t/ha. The 219 million ha of nonfederal pastureland and rangeland account for 1.4 billion metric tons of soil lost from sheet and rill erosion. The loss on nonfederal forest land is about 395 million t; the average annual rate is 2.6 t/ha, but the rate is six times higher on grazed than on nongrazed forest land. Soil lost by wind erosion, estimated for 209 million ha of land in 10 Great Plains States, annually amounts to 1.4 billion t. About 61 percent of this loss is from cropland and 38 percent is from rangeland. The estimated average annual rate of wind erosion on cropland exceeds 11.2 t/ha in three of the 10 states.

Effects of antecedent soil moisture on rill erodibility and critical shear stress

Comparison of loess and purple rill erosions measured with volume replacement method

Investigations on temporal and spatial variation of slope-scale SOC erosion and deposition

The influence of tillage practices on soil detachment in the red soil region of China

Comparative study of soil erodibility and critical shear stress between loess and purple soils

Determination of rill erodibility and critical shear stress of saturated purple soil slopes