| Dongzhi plateau,known as the first loess plateau in the world,continues to shrink,and its erosion gully heads even extend to the edge of the city.In order to slow down the shrinking of the plateau,the state has issued a series of policies of Gully Consolidation and Highland Protection(GCHP)Project.However,the project is still in the exploration stage,and there are many practical problems,such as the best governance model.In this paper,combined with the current situation of the gully protection project,the mutual feed mechanism between the project of GCHP(gully head landfill)and the hydraulic erosion is quantitatively evaluated in the watershed.Based on SWAT model,Yanwachuan(YWC)watershed is selected as the research target area to explore the scientific ecological restoration model of gully head landfill area.The main conclusions are as follows:(1)There is a chain relationship of mutual coupling,mutual promotion and connection among various erosion types in the gully area of the Loess Plateau.The specific performances are as follows: erosion gullies are developed on the surface of the plateau scoured by runoff,headwaters of erosion gullies are developed to erode the surface of the plateau;erosion gullies developed provide the foundation for the collapse and landslide of the valley,and the collapse and landslide cause the expansion of the gully bank.(2)SWAT model after parameter adjustment has good applicability in YWC watershed.After verification,the model efficiency coefficient of the regular runoff simulation value is0.83,the correlation coefficient is 0.89,the model efficiency coefficient of the runoff simulation value in the verification period is 0.74,the correlation coefficient is 0.86,which shows that SWAT model can be better applied to YWC watershed.(3)SWAT model simulate the situation that the project of GCHP(gully head landfill)was implemented,which shows the runoff of the sub watershed decreased significantly.The runoff of No.2 sub-catchment in YWC watershed decreased by 1.82%-2.48% compared with that in natural state after the gully head was buried.There are differences in runoff reduction among different ecological restoration measures: Grassland(2.48%)>forest land(2.21%)>cultivated land(1.93%)>bare land(1.82%),which shows that grassland has a good role in water conservation.(4)The development of hydraulic erosion can be slowed down by the scientific project of GCHP(gully head landfill).Comparing the simulated sediment yield of different ecological restoration measures and no measures,it was found that: cultivated land(102.08%)>no measures(100%)>bare land(97.84%)>grassland(31.12%)>forest land(30.66%).The results show that the project of GCHP(gully head landfill)can reduce the hydraulic erosion intensity,and the sediment yield decreased by 69.34% when the landfill area was covered by forest land.(5)Through hydrological analysis,it is found that the water flow path of gully head catchment area will be changed when the the project of GCHP(gully head landfill)been Carried out,making the flow path shorter and more numerous.The development of ground fractures and cave-holes along the edge of the catchment plateau provides advantageous channels for water flow.In the absence of necessary maintenance,it is easy to develop new gully heads in the long run,thus promoting greater hydraulic erosion in the watershedThere is the mutual feed mechanism between the project of GCHP(gully head landfill)and the hydraulic erosion.In order to reduce the shrinking rate of plateau surface and slow down the development of hydraulic erosion in the watershed,it is an important exploration direction for the future gully protection project to use ecological measures to control the exposed surface of gully head landfill area(for example,landfills are covered with grass). |
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