Characteristics And Sensitivities Of The Gravity Erosion On The Loess Plateau,China

Gravity erosion is the main form of soil erosion and one of the main erosion types on the Loess Plateau.However,the study of gravity erosion mechanism is slow due to the complex cause of gravity erosion and the nonlinear correlation of control factors.Based on the previous field survey data,the ArcGIS and remote sensing and revised increase-rate-analysis method(RIRA)were used to evaluate the distribution of the gravity erosion and the sensitivity of the gravity erosion on the topography factors in the Baota District,Yan'an City.The main studying contents are shown as follows:(1)RIRA is enriched and improved.RIRA takes independent variables with large absolute value of sensitivity coefficient as the priority,sorts and calculates the data of each line with the same dependent variable,and obtains the sensitivity of each factor to the physical phenomenon to be studied.This paper reviews the application of this method in other projects,and compares and analyzes the application of this method and other sensitivity analysis methods in the same study area.(2)The distribution of gravity erosion in scale,space and topography is analyzed.The results show that: i)The small-scale and medium-scale gravity erosion had a high frequency and the large-scale gravity erosion had a low frequency,but the large-scale gravity erosion greatly contributed to the total amount of the gravity erosion.ii)The plane distribution of gravity erosion in the study area was affected by the river distribution.92.7% of the gravity erosion occurred within the range less than 3000 m from the river.The vertical distribution of gravity erosion is concentrated within 1000-1100 m elevation range.iii)The gravity erosion tends to occur on sunny slopes.Landslide is most likely to occur in the area with low vegetation coverage.In the area with 10%-70% of the vegetation coverage,the vast majority of gravity erosion was distributed on sunny slopes.The gravity erosion in the convex slope was the easiest to occur,and the gravity erosion in flat slope and convex slope was concentrated on the sunny slope.iv)Whatever the slope direction was,the gravity erosion was common within the slope of 20 ° to 30 °.(3)The sensitivity of different gravity erosion types to changes in topographical factors was compared.The results show that: i)The change of slope,distance from the river and vegetation coverage had a greater impact on avalanche,and the sensitivity parameters were 7.6,25 and 60 times of that of the landslide.The landslide was more sensitive to the change of slope curvature and elevation,and the sensitivity parameters were 3 and 20 times of that of the avalanche.ii)The change of vegetation coverage leads to the difference of triggering between avalanche and landslide,followed by distance from river,elevation,slope and slope curvature.(4)The sensitivity of topographic factors to gravity erosion triggers was analyzed.The results show that: i)The slope gradient was the most important influential variable.The total amount of gravity erosion,amount of landslide and amount of avalanche were all positively correlated with the gradient and their sensitivity parameters on the slopes were 60.5,1 616.6 and 89.3,respectively.ii)For the total amount of gravity erosion and amount of landslide,the distances to the streams and altitude were the secondarty important factors.For the amount of avalanche,the vegetation cover and slope curvature were the secondary important factors.