Soil moisture is a key process in the hydrological cycle. During ecological restoration of the Loess Plateau, soil moisture status has undergone important changes, and infiltration of soil moisture during precipitation events is a key link affecting water distribution. Our study aims to quantify the effects of vegetation cover, rainfall intensity and slope length on total infiltration and the spatial variation of water flow. Infiltration data from the upper, middle and lower slopes of a bare slope, a natural grassland

Slope length is an important topographic factor for controlling soil erosion. There exists limited knowledge of the interactions of slope length, vegetation restoration, and rainfall intensity on soil erosion. This study investigated the impact of the slope length on soil erosion for different grass coverages and different rainfall intensities via simulated rainfall experiments. The experiments included five rainfall intensity treatments (1, 1.5, 2, 2.5, and 3 mm min−1), four grass cover treatments (0%, 30%, 60%, and 90%), and five slope length treatments (2, 4, 6, 8, and 10 m). The change process of soil loss was significantly different (p < 0.05) for different slope lengths. The trend of soil loss changing with slope length is: under a grass cover of 0 or 30%, the soil erosion increased exponentially with increasing slope length. However, under a grass cover of 60%, the soil erosion rate peaked at a slope length of 8 m, and under a grass cover of 90%, the soil erosion rate peaked at a slope length of 6 m. At rainfall intensities of 1.5–2 mm min−1, the overall soil erosion amount was small. The soil loss increased drastically with slope length when the rainfall intensity exceeded 2 mm min−1. Compared with a slope length of 2 m, longer slope lengths increased the erosion rate by 225–930% under different grass coverages treatments. Regression analysis showed that grass cover and rainfall intensity change the trend of erosion with slope length, and the negative effect of slope length on erosion is strengthened with the increase of grass cover, while this negative effect gradually weakens with the increase of rainfall intensity.

Soil properties play an important role in rill development and erosion. In this investigation, rill morphology developmental processes under sandy loam (SL), light loam (LL), medium loam (ML) and heavy loam (HL) soils on the Loess Plateau, China, were compared using laboratory experiments. Experimental analysis included two rainfall intensities (90 and 120 mm/h) and four slope treatments (0°, 15°, 20° and 25%). Results indicate that HL is the most prone to rill development, and SL, LL and ML are prone to rill development under heavy rain, with SL rill erosion being the most sensitive to heavy rain. The development of rills in SL are mainly characterized by an increase in rill width and merging nodes; rills in HL were mainly characterized by an increase in rill length, merging nodes and rill number. LL and ML rill development indices were between SL and HL. Differences in runoff collection caused by rill morphology differences further promoted differences in soil erosion. Rainfall intensity has a positive effect on rill shape parameters of all soils; slope has a positive and negative double effect on SL, LL and ML rill shape parameters, and only a positive effect on HL rill shape parameters. The sensitivity of rill parameters to rainfall intensity and slope angle depends on soil infiltration performance, surface soil stability and soil structure stability. Based on soil characteristic factors and rill morphological parameters, an empirical model of slope erosion in the loess region was established.

Field studies on the slope length effect of grass cover and rainfall intensity on erosion on typical watersheds of the Loess Plateau, China zimiao he 1 , peiqing xiao 2 , shilong hao 2 , ziqiang liu 3 , guodong jia 1 , and xinxiao yu 1

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