Abstract: Fix-bed experiment was conducted at the conditions of 3 slope gradients (5°, 10°, 15°), 9 unit discharge (0.2~0.6 L·m^-1·s^-1), 4 vegetation coverage (0, 1.7%, 3.5%, 6.1%) and 4 surface roughness (0.009, 0.12, 0.18, 0.38) to reveal the relationships among overland flow velocity and 4 factors. It was shown that overland flow velocity varied from 0.25 to 0.60 m·s^-1 under experiment conditions. Overland flow velocity increased with increasing discharge by power function, and increased with increasing slope gradient, while decreased with increasing surface roughness and vegetation coverage on all slopes. The contribution rate of above factors on overland flow velocity decreased in the order of slope gradient (0.821)>discharge (0.358)>roughness (-0.287)>vegetation coverage (-0.123). The main energy consumption was water flow against resistance (m>0.5), while minor energy consumption was converted into kinetic energy. Overland flow against resistance tended to increase with increasing surface roughness. When vegetation cover was the largest, energy consumption in resistance was the highest. However, there was no notable difference when vegetation cover was low.

Key words: overland flow velocity, vegetation coverage, roughness, flow-state indicator