Abstract
This paper treats the resistance to shallow water flows over a channel bed roughened with spheres. The drag force for spherical roughness element and the frictional resistance for the bed between roughness elements are separately measured by using a shear meter. The magnitude of the drag coefficient decreses with increasing roughness element concentration due to the shade effect which becomes more obvious as the relative water depth to roughness height increases. For the flows whose relative water depth is smaller than unity, the magnitude of the coefficient of frictional resistance increases with increasing water depth and roughness element concentration. Thus, the characteristics of resistance to shallow water flows which differ from the resistance law already established for deep water flows are revealed.
