| The sand-covered slope formed by the wind erosion deposited sediment is an important undersurface type of wind and water erosion crisscross region,and the wind erosion sedimentation has an important influence on the water erosion process.The paper choose the sand-covered slope of wind and water erosion crisscross region as the research object,the indoor simulation rainfall experiments was adopted,studied the runoff and sediment yield in the rainfall process under different sand-covered conditions,analyzed the runoff erosion and sediment yield dynamic characteristics of sand-covered slope,to establish the relationship between the rainfall runoff power and sediment yield,and illustrated the sediment particle distribution and variation characteristics in the different stages of time;Based on the 3d-laser scanning technology system,systematically analyzed the characteristics of micro-topography,identifies the space source of erosion and sediment on the slope.Constructed the response relationship between sediment yield and micro-topography change.In order to further elucidate the mechanism of sediment yield and the study of geomorphological changes in wind and water erosion crisscross region.The main innovative results are as follows:(1)Analyzes the characteristics of runoff and sediment yield in the simulated rainfall under sand-covered condition.The initial runoff time of sand-covered slope was delayed by the increase of the thickness and the length of the sand-covered,which was 10?23 minutes later than the loess slope.The peak value of runoff was increased with the increase of sand-covered thickness and length,and the peak time of sediment yield is delayed with the increase of the thickness and the length of sand-covered.The rate of runoff and sediment yield in different overburden conditions is larger than that of loess slope.The sediment yield of the sand-covered slope increased by 1.6?22.3 times than the loess slope.The relationship between the cumulative runoff R and the cumulative sediment yield S of different sand-covered conditions is satisfied with the power function,which is described as S=ARB(P<0.01).(2)Explained the temporal and spatial variation characteristics of the main hydrodynamic parameters of rainfall runoff on sand-covered slope,revealed the relationship between hydrodynamic parameters and runoff and sediment yield.Compared with the loess slope,the runoff Reynolds number Re increased by 0.39?3.30 times,and the Froude Numbers number Fr increased by 0.05?1.29 times,and the resistance coefficient f increased by 0.05?1.55 times.The relationship between the flow rate and the sediment yield rate and the hydrodynamic parameters can be described by y=ax+b,Reynolds number Re and relative depth manning roughness n/h can better represent the process of sediment deposition on the sand slope.(3)Clarifies the water content and infiltration characteristics of the sand-covered slope.The average water content of sand-covered slope is significantly greater than that of the loess slope.The infiltration volume before slope surface runoff was significantly greater than that of the loess slope,and the infiltration reduction was only in a good linear relationship with the sand-covered thickness(R2=0.72,P<0.01).Under different sand-covered conditions,the fluctuation degree of infiltration after runoff and the decrease trend are more severe than that of the loess slope.The infiltration rate of different sand-covered conditions showed a decrease trend with the duration of runoff.(4)Revealed the relationship between runoff erosion and sediment yield.The shear force of runoff on the sand slope was 0.67?2.81 times higher than that of the loess slope.The runoff power under the sand-covered slope increased by 0.10?0.55 times.The runoff rate of slope runoff increases with the increase of shear force and runoff power.The relationship between Dr and ?,and co,were established,respectively.The results indicated that the rate of Dr increased with the increase of ? and ?.Their relationship could be described as y=axb.The runoff energy of rainfall increases with the increase of the thickness and length of sand-covered.The runoff energy consumption of slope surface is always greater than that of loess slope.The total amount of sediment yield increases with the increase of runoff erosion power,and the relationship between them is power function.The total a mount of sediment yield increased with the increase of runoff erosion power,and the relationship between total sediment yield and runoff erosion power can be expressed as y=axb.(5)Clarified the transport characteristics of sediment particles at different erosion stages in sand-covered slope and revealed the spatial source of sediment.Most of the coarse particles in the slope were washed away within 0?10 min after the appearance of runoff.Bimodal distribution of sediment particles was observed during different rainfall periods under sand-covered slope.In the stage of the interrill erosion,the runoff first carries the sediment with a particle size greater than 0.054 mm,that is,the wind sand covered by the slope is washed away by the runoff first.In the stage of rill erosion,the runoff mainly carries the sediment of less than 0.054 mm,that is,the sediment source is in the loess;The sediment concentration was mainly larger than 0.054 mm in the 0?10 min after runoff.In the later period of production(after 10 min),the erosion of sediment mainly consists of particles less than 0.054 mm.It is shown that the erosion particles of sand-covered slope is mainly mixed with sand and loess.(6)Based on the analysis of slope erosion micro-topography,identified the spatial source of sediment,and constructed the response relationship between the micro-topography change of the overlying slope and the sediment yield.The experimental results show that the micro-slope and roughness of the sand-covered slope are always greater than that of the loess slope,however,the surface fluctuation and surface cutting degree of the sand-covered slope are smaller than that of the loess slope.The section 6#is the most serious position of erosion.The relationship between runoff,sediment yield,water infiltration rate,hydrodynamic para meters,soil energy characteristics and surface roughness could all be expressed as y=ax+b. |
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