Mathematical simulation of trapping sediment capacity of the single seabuckthorn flexible dam in the Pisha Sandstone area: A case study of EG1 in Zhun-ge-er county of Inner Mongolia, China

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In northwestern China, Pisha sandstone area with more than 11,000 km2 is located in an joint triangle region of Inner Mongolia Autonomous Region, shaanxi and shanxi province. The typical feature of the Pisha Sandstone is extremely hard when it is dry but becomes loose and soft when wet. This cause makes it have extremely severe impacts on local environment such as soil erosion and water loss, and damage the biological diversity. The soil erosion index of this area is nearly 30 000 t km-2 yr-1. In order to control erosion and restore the eco-environment of the gullies in this area, the seabuckthorn flexible dam actually being a new biological measure was proposed by Mrs. Bi, in which many researchers were very interested. Presently, this new measure has been successfully used to diminish the erosion rate of the area. In this paper, firstly, the major factors influencing the trapping sediment capacity of the seabuckthorn flexible dam were identified and determined. Then, the trapping sediment capacity of the single seabuckthorn flexible dam (that is to say there is only one seabuckthorn flexible dam in the modeled gully bed.) was simulated using one-dimensional sediment-flow model in this article. Finally, based on the computational results, two major impact factors, i.e. roughness and dam length of the seabuckthorn flexible dam, were found. Moreover according to the sediment retention effects of different groups assembled by different roughness with dam length, a series of the suitable length ranges of the seabuckthorn flexible dam were provided in corresponding to a series of the seabuckthorn flexible dam's roughness when the gully bed slop was determined as 0.01 (this slop belongs to the smaller one.). The results suggest that the seabuckthorn flexible dam can most effectively reduce sediment loss from the gully channel. To attain at least good eco-environment status, a future emphasis should be placed on widely spreading and planting of the seabuckthorn flexible dam in the Pisha sandstone area in order to powerfully control soil and water loss.