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| Runoff-sediment effect of “fully filled” check dam and related prevention and control measures |
| GAO Haidong1,2, JIA Lianlian3, PANG Guowei4, YUAN Shuilong2 |
1. School of Civil Engineering and Architecture, Xi'an University of Technology, 710048, Xi'an, China;
2. Key Laboratory of Northwest Water Resources and Environment Ecology of Ministry of Education at Xi'an University of Technology, 710048, Xi'an, China;
3. Upper and Middle Yellow River Bureau, Yellow River Conservancy Commission of the Ministry of Water Resources, 710021, Xi'an, China;
4. College of Urban and Environmental Science, Northwest University, 710127, Xi'an, China |
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Abstract [Background] Large-scale check dams in the Loess Plateau of China play a key role in sediment reduction and regional environmental improvement in the Yellow River basin. However, changes in the effects of runoff-sediment and related prevention and control measures on check dam under full capacity conditions have been rarely studied. [Methods] Based on geospatial data, we employed the RULSE and GAST hydrodynamic model to calculate soil erosion modulus and flow velocity, respectively.[Results] Here, we analyzed check dam once they reached full capacity, with the following changes found: 1) within the check dam control area, the surface slope and gully channel gradient both decreased, flow length was shortened, and the cross-section evolved from a V-shaped gully to a U-shaped gully; 2) using RUSLE computations and Guandigou No. 4 check dam as an example, the mean soil erosion modulus within the check dam control area was 4 472 t/(km2·a) before the check dam was built, but this decreased by 10% to 4 019 t/(km2·a) after the check dam was fully filled, thus in-situ erosion reduction was significant and sediment retention occurred from check dam construction to full capacity; 3) runoff flow velocity fell significantly from 0.83 m/s before construction to 0.27 m/s after the check dam reached capacity, but runoff flow velocity on the outer slope of the check dam increased significantly, in particular, the maximum runoff flow velocity at the bottom reached 3.76 m/s; and 4) "off-site" erosion reduction of the check dam decreased once the check dam reached full capacity. [Conclusions] Based on the above changes observed under the extreme siltation conditions, the following prevention and control measures are proposed: 1) spillway-based flood discharge works should be established in the gully channels of all catchments to improve connectivity within a branch gully and between branch and main gullies, thereby increasing flood discharge capacity; 2) the planting of trees and grasses and creating terraced fields built with local conditions considered should be undertaken to enhance slope erosion control, reduce flood and sediment supply to the slope surface, dissipate water erosion energy on the slope surface, and lower the risk to dam farmland after full capacity is reached; and 3) catchwater drains and drainage ditches, as well as engineering and vegetation measures, should be implemented to help prevent and control dam and steep slope erosion and increase vegetation cover of the outer slopes of a dam body. The results of this study are intended to provide scientific evidence to help improve check dam construction in the Loess Plateau of China.
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Received: 10 May 2016
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