EFFECTIVENESS OF EROSION CONTROL MEASURES ON QINGHAI-TIBET HIGHWAY SLOPES

To understand the characteristics of road erosion and find effective control measures,runoff plots were set up on Qinghai-Tibet roadside slopes (fillslope).After two-year study (2003 and 2004),it is found that (1) It is obvious for engineering measures to control runoff and soil loss.The reduction percent of run- off (soil loss) was 38.83%(81.89%)and 48.72%(95.81%),respectively in 2003 and 2004.The effects of drain water from road surface showed that road surface water was also an important driving force for ero- sion on roadside slopes.To predict soil loss more accurately,runoff from road surface should be considered in building erosion prediction model.In addition,controlling road surface runoff would efficiently minimize soil erosion on roadside slopes.(2) Grass measures only showed some effects in controlling erosion;how- ever,the effects of natural grass proved that planted grass would have great potential effects on soil erosion control if they were well established.(3) Engineering control measures could intercept runoff and sedi- ment at initial stage just after construction,keeping water and nutrient and promoting vegetation growth, which would increase the capacity of vegetation in intercepting runoff and sediment.So the combination of two measures is the most effective way to control runoff and soil loss,all combined measures could reduce more than 40% of runoff and more than 97% of soil loss.