Statistical Roughness Properties of the Gravel Bed Surfaces in a Meandering Channel

To investigate the statistical roughness properties of gravel bed surfaces in meandering channels, a meandering channel model is constructed, the flowrate is selected as the control variable, and the cross-sectional water levels, cross-sectional velocities and bed surface elevations are measured. The experimental results show that the elevation probability distributions of the detrended water-worked bed surfaces in the meandering channel are positively skewed and leptokurtic. With the increasing flowrate, the elevation standard deviation and the elevation skewness increases, but the elevation kurtosis decreases. The armoring layer in the meandering channel can resist a certain extent of increasing flow strength, but its protective ability is very limited. Once the armoring layer is destructed, the bed surface roughness will increase significantly. The bed surface roughness and the averaged influence scale of the constituent grains are large in the main stream path, while those in the main stream separating areas are small and decrease along the longitudinal direction. For any local zone, the roughness and the averaged influence scale in the longitudinal direction are obviously larger compared with the corresponding values in the lateral direction.