Experimental study on typical parameters of thin layer flow of urban underlying surface under different rainfall conditions

Based on the rainfall intensity of the future science and technology city in Changping, Beijing, the experiments were taken through the indoor rainfall test platform. The changes of roughness coefficient, resistance coefficient and runoff coefficient of four typical impervious underlying surface (asphalt, concrete surface, SBS and concrete square brick) and four typical permeable underlying surface (lawn brick A, lawn brick B, aeolian sand brick A and aeolian sand brick B) were studied under eight kinds of constant rain intensity. The results show that the plane size, surface smoothness and material have obvious influence on the roughness and resistance coefficient of impervious underlying surface, while structure and material have obvious influence on the roughness and resistance coefficient of permeable underlying surface. The roughness value and resistance coefficient of these two types of underlying surface decrease with the increase of rain intensity. But the variation range is small, and then tends to be stable gradually. The runoff coefficient of these two types of underlying surface keeps relatively stable under different rainfall intensity.