The Effects of Types of Flow on Manning's Roughness Coefficient

It is clearly that the roughness coefficient needs to be corrected in hydraulic calculations for open channel flow.Based on the concept of type of flow and experimental results,this paper shows that the roughness coefficient decreases with increasing of the depth of flow in an uniform flow,and increases with increasing of the depth of flow and energy gradient in non-uniform flow with M1water surface profile performed.In this paper,the two-steps method proposed to give an available method to determine roughness coefficient in non-uniform flow in which the depth of flow vary with distance,so it is difficult to establish a relationship between roughness coefficient and depth of flow.