Simulation of sediment retention effects of the single seabuckthorn flexible dam in the Pisha Sandstone area

Pisha Sandstone area is located in an adjacent region close to Inner Mongolia Autonomous Region, Shaanxi and Shanxi province of northwestern China, which covers an area of more than 11,000 km2. Pisha Sandstone is a kind of loosely bonded sandstone formed during the tertiary period. It is very hard when it is dry but becomes loose when wet. Due to the nature of that, this area of northwestern China is plagued with a high erosion rate (over 20,000 t km−2 yr−1) as well as poor vegetation. In order to reforest gullies and to control erosion in this area, the seabuckthorn flexible dam that is actually a new biological measure focused on by many people was successfully used to reduce the erosion rate of the area. This paper aims at the identification and/or determination of the major impact factors which essentially influence the sediment retention effects of the seabuckthorn flexible dam. Firstly, the sediment retention effects of the single seabuckthorn flexible dam were simulated using one-dimensional sediment-flow model in this study. Then, based on the computational results, two major impact factors, i.e. roughness and dam length of the seabuckthorn flexible dam, were found. Finally, according to the sediment retention effects under various roughness and dam lengths condition, a series of the suitable length ranges of the seabuckthorn flexible dam were given in corresponding to a series of the seabuckthorn flexible dam's roughness. The results show that the seabuckthorn flexible dam can strikingly and effectively reduce sediment loss from the gully. An emphasis is placed on widely spreading and planting of the seabuckthorn flexible dam in the Pisha Sandstone area in the future to prevent soil and water loss and to achieve at least good ecological status.