Experimental Study On The Characteristics And Mechanism Of Slope Erosion Of Different Vegetation Patterns In Loess Region Of Western Shanxi Province

The exploration of the influence of different vegetation patterns on sediment yield on eroded slopes and erosion mechanism is of great significance to the prevention and control of soil erosion and vegetation restoration in the Loess Plateau.This paper regards the typical natural wild grass ground in the gully region of the Loess Plateau as the research object,builds the runoff plots with different vegetation patterns,and tests the plots by field rainfall simulation and runoff washout.And it studies the characteristics of slopes with different vegetation patterns on runoff production and sediment yield,analyzes the dynamic characteristics of runoff erosion and sediment yield of slopes with different vegetation patterns,and establishes the relationship between erosion dynamics and sediment yield.It also analyzes morphological characteristics of rills on slopes,discriminates spatial erosion distribution and sediment source of slopes with different patterns,and provides theoretical support for the mechanism of sediment yield on eroded slopes with different vegetation patterns.Special results are as follows:(1)The flow pattern of slope runoff belongs to rapid transition flow pattern,but the flow pattern tends to slow transition flow pattern after planting vegetation pattern,and the flow patterns of the middle pattern(the pattern C)and the lower pattern(the pattern D)tend to slow transition flow the Pattern.The runoff velocity,runoff shear force and runoff power are positively correlated with the scour discharge.There were little differences in velocity,runoff shear force and runoff power among the three the Patterns(the pattern B、the pattern C and the pattern D).The flow velocities at different scour discharge are shown to be that the bare land(the pattern A)> the upper pattern(the pattern B)> the middle pattern(the pattern C)> the lower pattern(the pattern D).Under the three kinds of scour discharge,the slow down rate of flow velocity by the pattern D is 22.37%-29.09%,the reduction range of runoff shear force is 10.53%-20.74%,and the runoff power is reduced by 5.45%-13.87%.(2)The width depth ratio of rill on slope is negatively correlated with the scour discharge.The ratio of rill width to depth and the degree of rill fragmentation of the bare land(the pattern A)were the smallest,and the rill shape on the slope was "narrow deep type".While The ratio of rill width to depth and the degree of rill fragmentation of the middle pattern(the pattern C)were the largest,and the rill shape on the slope was "wide shallow type".(3)There is a negative correlation between the initial runoff generation time and the scour discharge.With the increase of the scour discharge,the slow flow effect of vegetation will be smaller and smaller.The initial runoff time,runoff yield and sediment yield of different patterns are as follows: the lower pattern(the pattern D)> the middle pattern(the pattern C)> the upper pattern(the pattern B)> the bare land(the pattern A).The runoff yield and sediment yield of the lower pattern(the pattern D)is the smallest,and the benefit of runoff reduction is 4.10%-14.16%,and the benefit of sediment reduction is 34.57%-64.64%,which is the best pattern of soil and water conservation.(4)Soil erosion rate was significantly correlated with runoff shear force and runoff power(P < 0.01),and significantly correlated with average velocity(P < 0.05)under three scour discharge.Runoff shear force τ is the most relevant factor of soil erosion rate.The correlation between soil erosion rate and rill average depth and rill width depth ratio was good(P < 0.05),and the correlation between soil erosion rate and rill average depth was extremely significant(P < 0.01).The average depth of rill is the best correlation parameter with soil erosion rate.(5)The volume and location of erosion patches were different in the four patterns,and the largest erosion area of the bare land(the pattern A)was in the middle of slope.Compared with the bare land(the Pattern A),the middle pattern(the pattern C)erosion volume was the smallest,which decreased by27.47%.Although the volume of erosion patches of the lower pattern(the pattern D)was second only to the bare land(the pattern A),the sediment yield was the smallest.Therefore,vegetation in the middle and lower part of the slope was beneficial to control erosion and intercept sediment.