Adapting the WEPP hillslope model to predict unpaved road soil erosion
in southern China
Abstract
Process-based erosion models are efficient tools that can be used to
predict where and when erosion occurs. On unpaved roads that have been
recognized as important sediment sources, soil loss along road segments
should be precisely predicted. This study was performed using the
hillslope version of the Water Erosion Prediction Project (WEPP) to
estimate soil loss from 20 typical road segments in the red soil region
of South China. Terrestrial laser scanning (TLS)-measured soil losses
were used to validate the model simulations. The results showed that the
WEPP model could reasonably predict the total soil loss in relatively
short (less than 100 m) and gentle (slope gradient lower than 10%) road
segments. In contrast, the WEPP-simulated soil loss was underestimated
for long or steep road segments. Detailed outputs along roads revealed
that most of the peak soil loss rates could not be adequately
calculated. The linear critical shear stress and the sediment
equilibrium theory in the WEPP model for soil detachment simulation
might be responsible for the underestimation. Additionally, the lack of
upslope flow and the curved road tortuosity were found to be connected
to the relatively low efficiency of the model outputs. Nevertheless, the
WEPP simulation could accurately fit the trend of soil loss variation
along road segments despite underestimation. Furthermore, the simulated
results could provide a reliable prediction of the maximum soil loss
positions. Therefore, the WEPP model could be adopted to evaluate the
erosion risk of unpaved roads in the red soil region of South China.