Experimental study of critical flow energy for slope erosion under the influence of vegetation cover

The critical flow energy for slope erosion is an important characteristic value measuring the erodibility of a soil.Using simulated rain of three intensities(45 mm/h,87 mm/h and 127 mm/h),an experiment study was conducted on the critical flow energy for slope erosion under different underling conditions.The experiments were made for bare soil,grass and shrub slopes of gradient 20°.The result shows that the sediment transport rate can be linearly related to the flow energy and to the fluid shear stress under all underling conditions.Such a linear relation appears to be validated for the unit stream power and the specific energy.The critical shear stress values are respectively 0.86 N/m²,2.86 N/m² and 1.65 N/m² for bare soil slope,grass slope and shrub slope; while,the values for the critical unit stream power are 0.003 6 m/s,0.0127 m/s and 0.0169 m/s,and values of 0.074 cm,0.11 cm and 0.13 cm are found for the specific energy.The study reveals that larger critical flow energies would be required for slope erosion under vegetated conditions compared to that of bare soil.The experimental data provides a valuable asset for the mechanism study of water and sediment yields under the influence of vegetation cover,which is important to the ecological rehabilitation projects.