Rill network development on loessial hillslopes in China |
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| Authors: | Haiou Shen Fenli Zheng Xunchang John Zhang Chao Qin |
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| Institution: | 1. State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Institute of Soil and Water Conservation, Northwest A&F University, Yangling, China
College of Resources and Environment, Jilin Agricultural University, Changchun, China;2. State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Institute of Soil and Water Conservation, Northwest A&F University, Yangling, China;3. USDA-ARS Grazinglands Research Laboratory, El Reno, OK, USA |
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| Abstract: | Rill network development not only potentially affects hillslope and drainage network evolution, but also causes severe soil degradation. However, the studies on rill network development remain inconclusive. This study aimed to investigate the temporal and spatial development of hillslope rill networks and their characteristics based on rainfall simulations and field observations. A soil pan (10.0 m long × 3.0 m wide × 0.5 m deep) on a 20° slope was applied three successive simulated rains at two intensities of 50 and 100 mm h–1. The field observations were performed on two bare hillslope runoff plots (10.0 m long × 3.0 m wide) at 20°. Three typical erosive natural rainfall events were observed in the field, and rills were measured in detail, similar to the laboratory rainfall simulation. The results indicated that with increases in rainfall events, the rill network morphology varied from incipient formation to the maximum drainage network density. Four rill network development indicators (rill distribution density, distance between rills, rill bifurcation number, and confluence point number) exhibited different changes over time and space. Among the four indicators, the rill bifurcation number was the best indicator for describing rill network development. Rill flow energy increased and decreased cyclically on a slope ranging between ~3 and 4 m. Moreover, rill networks on loessial hillslopes generally evolved into dendritic rather than parallel forms. The development characteristics of the rill network were relatively similar between the laboratory simulation and natural field conditions. Over time, rill erosion control measures become increasingly difficult to implement as the rill network develops. The morphology of eroding rills evolved over time and space, which led to corresponding rill network development. Further study should quantify the impacts of rill network development on soil degradation and land development. © 2020 John Wiley & Sons, Ltd. |
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| Keywords: | rill erosion rill network rill development indicator spatial distribution field observation |
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