Abstract
Few data are available for estimating the sediment transport rate on a
steep slope of grass with different covers. In this study, the
artificial simulated rainfall test is used to investigate how rainfall
intensity, slope and cover affect the sediment transport rate.
Simultaneously, the study establishes a model for the sediment transport
rate using shear stress, stream power, unit stream power and unit energy
on steep grassland slopes. Results show that the sediment transport rate
decreases as the vegetation cover increases, as described by linear or
logarithmic equations under different rainfall intensities or slopes.
The sediment transport rate increases as an exponential function
equation with rainfall intensity, slope and cover with a Nash–Sutcliffe
model efficiency (NSE) value of 0.864. The effects of slope steepness
are stronger than the effects of rainfall intensity and cover.
Regression analyses show that the sediment transport rate can be
predicted from the power function equations of shear stress, stream
power and unit energy. In addition, the sediment transport rate can be
fit to unit stream power with linear equation (NSE = 0.840). However,
shear stress, stream power and unit energy perform poorly (NSE = 0.394,
NSE = 0.498 and NSE = 0.330, respectively). Further analysis shows that
the sediment transport rate is best modelled by a power function
equation that includes three factors, i.e. rainfall intensity,
vegetation cover and slope. Moreover, unit stream power results in the
best model for the sediment transport rate among the different
hydrodynamic parameters. The soil erodibility parameter and critical
unit stream power of this experiment are 113.59 and 0.216 m·s-1,
respectively, which are six times more than those in the bare slope. The
measurements and calculations of the sediment transport rate, the
calculations of the surface roughness and characteristic considerations
of the vegetation for sheet flow should be explored in future research,
which are important in improving experimental accuracy and sediment
transport rate modelling