Abstract:In order to study the changes of the hydraulic characteristics of overland flow, a series of laboratory flume simulation experiments were conducted on smooth and vegetated beds under three slope gradients, eight flow discharges and four vegetation spatial patterns. The results showed that:(1) The water level of grass covered slope was 1.02~1.38 times that of smooth glass slope, and the flow velocity was 6.52%~36.73% slower than that of glass covered slope. With the increase of flow discharge and slope gradients, the velocity increased with a power function (R2>0.95). (2) There was a significant linear positive correlation between Reynolds number and discharge (R2>0.99), but no significant correlation between Reynolds number and slope gradient and grass cover pattern. Grass cover effectively reduced Froude number on slope. (3) With the increase of discharges and slope gradients, the overland flow pattern of grass-covered slope changed from laminar-slow or rapid flow to turbulent-rapid flow. (4) With the increase of discharges, the overland flow resistance coefficient decreased with a power function (R2>0.86). Slope gradient had no significant effect on resistance coefficient (p>0.05). (5) The effect of raising water level was random pattern > patch > grass square > belt. The effect of slowing down velocity was random pattern > belt > patch > grass square. Froude number on slope was patch > belt > grass square > random pattern. The ability to resist erosion was random pattern > grass square > belt > patch.