Rill morphological change characteristics and influencing factors on different soil types in the Loess Plateau, China

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.