The road erosion of slope-gully was a typical type of erosion with ubiquity and intensity on the loess
plateau. 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 destroyed
due to producing extremely high runoff efficiency and scouring serious of which water and soil loss was
obvious higher than that of non-road area. At present, it is not realistic to change the majority production
road of slope of gully into asphalt road or cinder gravel road. Practice had proved that plant-covered road
was the most economical and effective way to solve this problem. Therefore, in this paper, taking
plant-covered road and earth road on the loess plateau-gully region as research object, the process of
erosion and sediment yield, characteristic of hydrodynamic and law of erosion sediment transport of road
were studied by using field water discharge scouring experiments, and the relationships between the factors
of 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 of
plant-covered road and earth road, the mechanism of plant protecting of road erosion was revealed, which
provided quantitative evaluation parameters and scientific basis for establishing system of plant protecting
erosion on the loess plateau-gully region, planning services for agricultural production, water conservation
and 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 the
experiment with the time changed, then decreased significantly and tended to stable about 10min. They
increased as the slope of road and flow discharge increased. Sediment yield rate has a negative logarithmic
relationship with the time under the same slope and different flow discharges. There was a logarithmic
relationship between sediment yield rate of earth road and slope under the different flow discharges, while
an 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 about
10min. In the condition of the same flow discharge, runoff rate of earth road have been in line with change
of the slope, while a parabolic shape was described for plant-covered road, which indicated that the effect
of slope increased on runoff velocity was well restricted by recovering vegetation.
(3) Reynolds number of earth road changed between 1205.3 and 15277.4, while it was
938.7-8049.4 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 to
2.44 and average value was 1.09, while it was 0.58 to 1.12 and average value was 1.09 for plant-covered
(4) The effect of plant-covered road reducing water was only 0.63% 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 was
33.09% to 81.42%.
(5) Flow shear stress, stream power, energy consumption of unit width increased with time. Under the
same slope and flow discharge, flow shear stress and stream power of plant-covered road were smaller than
that of earth road, and energy consumption of unit width was greater than that of earth road, which
indicated that plant-covered road had an effective action of preventing soil erosion.
(6) There was a linear relationship between soil detachment rate and variation hydrodynamic
parameters, and erosion critical value existed. The critical shear stress, critical stream power and critical
energy 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/(m2·s), 3.48 g/(m2·s) respectively.