| Soil erosion is an important influencing factor that threatens regional ecological environment and agricultural economic development.As one of the areas with more serious soil erosion in China and even in the world,the serious soil erosion of Loess Plateau takes away a large amount of soil and its nutrients,making the soil more and more infertile and seriously threatening the development of local agricultural economy.The proportion of fine gully erosion in soil erosion on the Loess Plateau can generally reach 60%-80%,so the study of fine gully erosion is undoubtedly also the focus of soil erosion research.As the most basic erosion unit in the hilly area of Loess Plateau,slope and gully system is also the main source of erosion and sand production.In this paper,the slope and gully system in the hilly area of Loess Plateau was studied,and six different slope and gully systems with different slope measures(control CK(bare slope),measure A(vegetation on slope),measure B(vegetation in slope),measure C(vegetation under slope)measure D(terraces in slope),measure E(grass on slope+ladder in slope),measure F(ladder in slope+grass under slope))were constructed,and through artificial simulated rainfall,based on 3D laser scanning Based on the 3D laser scanning technology,we clarified the changes of the development process of fine gully erosion and the regulation of fine gully erosion by different measures,quantified the hydrological connectivity of slope surface,and revealed the mechanism of different slope management measures on fine gully erosion.The main conclusions of the study are as follows:(1)In the regulation effect of each individual measure of vegetation and terraces on the slope infiltration process of the slope gully system,the size of the regulation effect on the total infiltration in the 1st and 2nd rainfall process is shown as measure C(116.71L,121.87L)>D(96.93L,90.17L)>B(56.78L,44.29L)>A(5.60L,4.38L),the magnitude of the regulation effect on the total infiltration when the vegetation and terraces are deployed together is shown as Measure F(228.06L,262.75L)>Measure E(186.31L,230.11L);the magnitude of the average infiltration rate during the whole 1 and 2 rainfall fields is shown as Measure F(8.48L/min,8.53L/min)>Measure E(7.48L/min,7.65L/min).min,7.65L/min)>measure C(5.46L/min,4.34L/min)>measure D(4.89L/min,3.36L/min)>measure B(3.69L/min,1.93L/min)>measure A(2.15L/min,0.68L/min);(2)In the regulating effect on the slope flow and sand production on the slope surface of the slope and gully system,the flow production of each vegetation and terracing measure during the 1st and 2nd rainfall were measure A(360.10L,408.67L),measure B(308.92L,368.76L),measure C(248.99L,291.18L),measure D(268.76L,322.88L),measure E(179.40L,182.94L),measure F(137.68L,150.30L),and the sand production of each vegetation and terracing measure during the 1st and 2nd rainfall was measure A(56.11kg,13.97kg),measure B(49.68kg,11.70kg),measure C(43.91kg,9.37kg),Measure D(46.81kg,10.99kg),Measure E(36.37kg,7.65kg),Measure F(30.04kg,5.26kg),among the single measures of vegetation and terraces,the water reduction effect in the 1st and 2nd rainfall showed that Measure C(31.91%,29.50%)>Measure D(26.51%,21.83%)>Measure B(15.53%,10.72%)>Measure A(1.53%,1.06%),and the sand reduction effect was best for Measure C(25.66%)during the 1st rainfall and Measure D(38.42%)during the 2nd rainfall.(3)In the regulating effect of vegetation and terracing measures on the development process of fine furrow erosion,measures A,B,C,D,E and F reduced the total length of fine furrows by 3.64%,8.10%,59.11%,73.68%and 79.76%,respectively,and delayed the moment of first obvious appearance of fine furrows by 2 min,6 min,12 min,10 min,13 min,18 min,respectively,18min or so,from the size of the average development rate of fine gully length,it shows the law of measure A(4.54cm/min)>measure B(4.41 cm/min)>measure D(3.30 cm/min)>measure C(2.30 cm/min)>measure E(1.51cm/min)>measure F(1.32cm/min),each measure respectively For the amount of fine gully erosion,volume of fine gully erosion and the size of the percentage of fine gully erosion were measure A(2.47%,3.38%,3.09),measure B(4.34%,15.19%,4.37%),measure C(27.12%,16.47%,27.12%),measure D(15.31%,21.61%,20.15%)measure E(36.60%,43.75%),measure F(50.14%,50.06%,44.22%),and the combined indicators show that among the single measures of vegetation and terraces,measure C has the best regulation effect on fine gully erosion,and among the combined measures of vegetation and terraces,measure F has a better regulation effect on fine gully erosion than measure E;(4)In the modulating effect of vegetation and terracing measures on the hydrological structural connectivity of the slope surface of the slope gully system,after the 1st rainfall,the vegetation and terracing measures caused the percentage of larger runoff length formed by the slope surface soil after each rainfall to decrease relative to the control group for measure A(0.33%),measure B(1.89%),measure C(3.62%),measure D(3.06%),measure E(3.97%),and Measure F(4.99%);after the 2nd rainfall,each measure caused the percentage of larger runoff length formed on the slope soil after each rainfall to decrease relative to the control group for Measure A(0.35%),Measure B(1.03%),Measure C(2.90%),Measure D(2.30%),Measure E(3.45%),and Measure F(4.81%),respectively.It can be seen that measure F has the greatest effect on the hydrological connectivity of the slope.In the statistical analysis of topographic convergence index and topographic moisture index,the skewness values of topographic convergence index under each measure are negative,indicating that the depressed terrain on the slope surface dominates relative to the raised terrain after each rainfall,and the average value of slope moisture index shows an increasing trend after each rainfall,indicating that the soil moisture on the slope surface is more likely to reach saturation and produce flow after the rainfall;(5)The synergistic effect of the combined configuration of vegetation and terraces for the flow reduction and regulation effect,the size of measure E(22.91%and 32.82%)and measure F(3.92%and 12.28%)during the 1st and 2nd rainfall,respectively,for the synergistic effect of the sand reduction and regulation effect,in which the size of the sand reduction synergistic effect of measure E and measure F during the 1st rainfall were 12.67%and 2.75%,during the 2nd rainfall,the magnitude of the synergistic effect of measure E and measure F for sand reduction is 19.55%and 4.38%,respectively.In the evolution of the synergistic effect of flow and sand reduction per min during the rainfall,both measure E and measure F have a negative value of synergistic effect for a certain length of time under the 1st rainfall,indicating that synergistic for measure E and measure F,the synergistic effect of flow and sand reduction The synergistic effect mainly occurred during the 2nd rainfall.In the synergistic effect of fine gully erosion volume,fine gully erosion volume and fine gully erosion area size,the synergistic effect under measure E was 18.82%,20.51%and 18.02%,respectively;the synergistic effect under measure F was 7.70%,2.79%and 13.78%,respectively.Thus,it can be seen that among the synergistic effect sizes for each variable of fine gully erosion,measure E showed better results. |
