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| Effects of repetitive rainfalls on rill erosion of coluvial deposit in granite slope collapse |
| Jiang Fangshi, Huang Yanhe, Lin Jinshi, Zhao Gan, Ge Hongli |
| College of Resource and Environment, Fujian Agriculture and Forestry University, 350002,Fuzhou, China |
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Abstract Colluvial deposits as a part of slope collapse are the packed material under the collapsing wall, which form the collapsing wall and original mountain slope surface under hydraulic pressure and gravity. As a type of disturbed soil, colluvial deposits feature high contents of gravel, sand, and loose materials that have a weak structure, low cohesion, poor stability, and high erodibility. Rill erosion is an important factor of soil erosion. The study of peculiarity of rill erosion will be of great significance to illustration of mechanism of the erosion on colluvial deposits. We investigated the sediment yield processes and the characteristics of rill development on colluvial deposits at repetitive rainfalls. Rainfall simulations were conducted in a 5 m2(5 m ×1 m) test plot (30°) in the laboratory. Rainfall intensity ranged from 1.00 to 2.33 mm/ min. Results are shown as follows. The sediment yield processes tended to be consistent during the later stages in the three rainfalls at the rainfall intensity of 1.00 mm/ min; while at rainfall intensities of 1.67 and 2.33 mm/ min, the consistency of sediment yield processes only occurred in the first two rainfalls, and sediment yield rate sharply increased at the later stage in the third rainfall. At all rainfall intensities, the distance of the longest rill head from top slope became short, the width and depth increased with the increasing rainfall times; the number of rills and the density increased but width-depth ratio decreased with the increasing rainfall times at the rainfall intensities of 1.00 and 1.67 mm/ min, whereas the opposite results were observed at the rainfall intensity of 2.33 mm/ min. The rill erosion volume and the contribution on slope erosion increased with increasing rainfall times at all rainfall intensities.
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Received: 03 April 2014
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