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Abstract: Vegetation recolonization has often been used to control roadside slope erosion, and in this paper, four restoration models – Natural Restoration, Grass, Grass & Shrub, Sodded Strip – were chosen to recolonize the plants on a newly built unpaved roadside slope in the Three Gorges Reservoir Area. After eight months growth, eight rainfall simulations (intensity of 90mmh−1 for 60min) and in-situ soil shear strength test were then carried out to identify the impacts of vegetation on roadside slope erosion and soil shear strength. The erosion on cutslopes was higher than that on fillslopes. The runoff coefficient and soil detachment rate were significantly lower on the Grass & Shrub model (4.3% and 1.99gm−2 min−1, respectively) compared with the other three, which had the highest surface cover (91.4%), aboveground biomass (1.44kgm−2) and root weight density (3.94kgm−3). The runoff coefficient and soil detachment rate on roadside slopes showed a logarithmic decrease with the root weight density, root length density and aboveground biomass. The soil shear strength measured before and after the rainfall was higher on Grass & Shrub (59.29 and 53.73kPa) and decreased on Grass (46.93 and 40.48kPa), Sodded Strip (31.20 and 18.87kPa) and Natural Restoration (25.31 and 9.36kPa). Negative linear correlations were found between the soil shear strength reduction and aboveground biomass, root weight density and root length density. The variation of soil shear strength reduction was closely related to the roadside slope erosion, a positive linear correlation was found between runoff coefficient and soil shear strength reduction, and a power function was shown between soil detachment rate and soil shear strength reduction. This study demonstrated that Grass and Grass & Shrub were more suitable and highly cost-effective in controlling initial period erosion of newly built low-volume unpaved road. [Copyright &y& Elsevier]

Roads play a significant role in altering hydrological processes. Roads cause more erosion to be generated from the hillslope for both road-concentrated flow and rainfall. In this study, six treatments (Natural Restoration, Grass, Grass & Shrub, Sodded Strip, Grass & Farmland, and Farmland) were used to recolonize hillslope plants on a newly built unpaved road. Rainfall simulation (rainfall intensity of 90 mm h − 1 and 120 mm h − 1 ) and scouring simulation (scouring flow rate 15 L min − 1 and 20 L min − 1 ) tests were conducted to identify the effects of plants on soil erosion. In the rainfall simulation test, Grass & Shrub was more effective at reducing hillslope erosion than the other treatments, and Grass & Shrub also had a lower runoff coefficient, soil detachment rate, and higher efficiency in trapping runoff and sediment. The hydrological responses of all of the tested plots in the scouring test were much faster than in the rainfall simulation, as indicated by the lower lag time to runoff generation. The hillslope erosion in the scouring test was significantly higher than in the rainfall simulation. The water-stable aggregate, saturated hydraulic conductivity, vegetation cover, root length density, and root weight density were important factors that conditioned the runoff generation and sediment yield from the hillslope in both experimental tests. In the scouring test, in infiltration improvement and flow erosivity reduction, Grass was more effective at trapping runoff and sediment because of its dense well-developed system of fine roots. Therefore, except for an immediate surface cover, in the areas where the hillslope has a risk of road-concentrated flow scouring, the enhancement of topsoil roughness was also very important in weakening the impact of road-concentrated flow on the hillslope. [ABSTRACT FROM AUTHOR]