Laboratory investigations of rill dynamics on soils of the Loess Plateau of China

We conducted a laboratory study on rill network evolution with detailed measurements under controlled experimental conditions. The concepts of fractal geometry, entropy and topology were used to quantify rill erosion intensity and morphology. The objectives of this study are to reveal rill erosion processes and rill network development under different rainfall intensities and to present some indicators to provide a quantitative description of rill morphology. A soil pan (5 m long, 1 m wide and 0.6 m deep with slope gradient of 20°) was subjected to three successive rainfall events under rainfall intensities of 66, 94 and 127 mm h− 1. The results showed that rainfall intensity played a major role in rill erosion. The development of a rill network is most rapid under medium intensity rainfall; rainfall intensity that is too weak or too strong is not conducive to rill development. As rainfall duration increased under the same rainfall intensity, the values of soil loss, rill density, geomorphologic comentropy and nodes increased. Rill network development was slow at the early stage but became more rapid at a later stage. The results also indicated that the geomorphologic comentropy was the best basic morphological indicator of rill erosion, and the number of rill nodes was the best derived morphological indicator of rill morphology, which was followed in descending order by the fractal dimension, rill density and bifurcation ratio.