| The road erosion of slope-gully was a typical type of erosion with ubiquity and intensity on the loessplateau. It cut off the original water line and collected most runoff of the part of the loess plateau, farmland,village and farmhouse, earth road often became staggered gully erosion, muddy and even was destroyeddue to producing extremely high runoff efficiency and scouring serious of which water and soil loss wasobvious higher than that of non-road area. At present, it is not realistic to change the majority productionroad of slope of gully into asphalt road or cinder gravel road. Practice had proved that plant-covered roadwas the most economical and effective way to solve this problem. Therefore, in this paper, takingplant-covered road and earth road on the loess plateau-gully region as research object, the process oferosion and sediment yield, characteristic of hydrodynamic and law of erosion sediment transport of roadwere studied by using field water discharge scouring experiments, and the relationships between the factorsof terrain slope, discharge, type of different surface conditions and so on and erosion and sediment yield,hydrodynamic parameters were revealed. By analyzing the difference characteristics of hydrodynamic ofplant-covered road and earth road, the mechanism of plant protecting of road erosion was revealed, whichprovided quantitative evaluation parameters and scientific basis for establishing system of plant protectingerosion on the loess plateau-gully region, planning services for agricultural production, water conservationand ecological construction in this region. Main conclusions showed as follow:(1) Sediment yield rate and flow sand concentration were the greatest at the beginning of theexperiment with the time changed, then decreased significantly and tended to stable about 10min. Theyincreased as the slope of road and flow discharge increased. Sediment yield rate has a negative logarithmicrelationship with the time under the same slope and different flow discharges. There was a logarithmicrelationship between sediment yield rate of earth road and slope under the different flow discharges, whilean exponential relationship between sediment yield rate of plant-covered road and slope was identified.(2) Flow velocity increased to the highest value about 5min, then decreased and tended to stable about10min. In the condition of the same flow discharge, runoff rate of earth road have been in line with changeof the slope, while a parabolic shape was described for plant-covered road, which indicated that the effectof slope increased on runoff velocity was well restricted byrecovering vegetation.(3) Reynolds number of earth road changed between 1205.3 and 15277.4, while it was938.7-8049.4 for plant-covered road. Froude number of slope runoff of road decreased with runoff duration under a certain slope and the different flow discharges. Fr of slope flow of earth road was 0.54 to2.44 and average value was 1.09, while it was 0.58 to 1.12 and average value was 1.09 for plant-coveredroad.(4) The effect of plant-covered road reducing water was only0.63% to 6.15%, which was not obvious;under the same slope and flow discharge, the decrement rate of sediment yield rate was 35.00% to 83.77%and reached the highest for 9°; The decrement rate of runoff sand concentration of plant-covered road was33.09% to 81.42%.(5) Flow shear stress, stream power, energy consumption of unit width increased with time. Under thesame slope and flow discharge, flow shear stress and stream power of plant-covered road were smaller thanthat of earth road, and energy consumption of unit width was greater than that of earth road, whichindicated that plant-covered road had an effective action of preventing soil erosion.(6) There was a linear relationship between soil detachment rate and variation hydrodynamicparameters, and erosion critical value existed. The critical shear stress, critical stream power and criticalenergy consumption of unit width of plant-covered road and earth road were 2.44Pa,3.36Pa; 0.36 N/(m·s),0.45 N/(m·s); 2.99 g/(m~2·s), 3.48 g/(m~2·s) respectively.
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