Calculation of overland flow resistance and hydraulic characteristics along slope distance in a steep experimental flume

A series of overland flow experiments were carried out on the smooth and adhering sand slope with the slope degree of 15°, 20° and 25°, respectively. The hydraulic parameters including velocity and depth were obtained in different flow, different slope location and discharge. Furthermore, the thin layer overland flow resistance characteristic was discussed according to the average Weisbach-Darcy coefficient method and improved calculating method considering the variations of hydraulic factors along slope distance. The results showed that the overland flow velocity and the depth varies from the monitoring distance in the experiment slope, e.g., the velocity increases with slope distance increase on smooth and adhering sand slope, however, the peak and lower value appears on the adhering sand slope with larger slope degree. On the other hand, the traditional resistance method, the average Weisbach-Darcy coefficient method is not feasible to analyze the flow resistance in smooth slope and roughness slope with steep degree, while improved method considering variations of hydraulic factors along slope distance may be better to calculate the overland flow resistance.