Research Of Water Erosion On Steep Weathered Pisha-sandstone Slope

Feldpathic sandstone is widespread among arid and semi-arid inter-region of Meng Jin Shaan, which contributed largely to erosion process and sediment yield, especially in steep slope. In order to determine how different herbaceous plant patterns influenced on erosion, 26 plots were built in Erdos where feldpathic sandstone existed, vegetation were planted in accordance with herbaceous plant pattern in the field, including individual pattern and clump pattern. Natural precipitation observation and simulated runoff experiments were proceeded successively. By observing experiment process and analyzing date, it could be concluded that:(1)Natural precipitation experiments revealed the least 30 min rainfall intensity causing sediment was 0.07 mm/min, the least rainfall was 10.2 mm. Correlation analysis didn`t find relationship between both rainfall and rainfall intensity with sediment yield and runoff yield. But it revealed significant relevance between sediment yield and runoff yield, moreover, determination coefficients were relatively large. Per runoff causing sediment among treatments when adopting whether linear regression or ratio of sediment yield to runoff yield revealed, with increase of distance of individual plant and clump(clump enlarged correspondence to increasing distance of clumps),erosion increased.(2)When distance of individual plant widened, runoff yield didn’t show consistent and regular trend. Whereas, with widening of distance between clumps, runoff decreased consistently. During the period of simulated runoff process, sediment yield happened mainly in early stage, sediment yield mounted to maximum after runoff appeared, and it decreased subsequently. Obvious sediment yield happened only within former 12 min of experiments. While increasing of distance of individual plant, sediment yield increased. Enlarging Clumps generally leaded to more sediment as well. Ratio of sediment yield to runoff suggested increasing distance, namely enlarging clump promoted sediment transport efficiency, so did wet sieving analysis which in same change process of distance and clumps showed average weighted diameter a roughly incremental trend,and particles whose diameter were larger than 1mm. Later stage showed larger average weighted diameter of particles. Rill deepening happened in early stage, roughly after runoff experiment started to early 4 min of experiment after runoff appeared, when depth of rill accounted for 43~84% of ultimate rill depth. Rills deepened gradually after 4th min but its rate decreased. It costed approximate 30 th min before rill deepening stopped developing. Maximum depth of rills was 24 mm. Abrupt runoff which happened abruptly and presented sheet may contributed to sediment producing in later period of experiments.(3)Because of dispersibility of runoff in slope, choosing a channel to measure and counted hydraulic diameters couldn`t be able to represent the whole hydraulic characteristics. It was necessary to adopt and develop more comprehensive parameter to study the effect of disperse runoff on erosion on slopes.(4)In condition of same plant density, individual plant pattern did better in preventing erosion of steep feldpathic sandstone slope rather than clump pattern.