Experimental Coefficient of Discharge for Leaky Woody Dams in Clear Water Conditions

Abstract

Natural flood management (NFM) uses natural features and processes to manage flood risk. Although natural processes in river flow are well known, their use to manage floods has been only deeply analyzed since recent years, and the hydraulic behavior and performance of some measures is not yet fully understood. Leaky woody dams (LWD) are one example of the application of NFM, which is very complex to understand, and many uncertainties are still unresolved. In practical applications, the effect of LWD is modeled with different assumptions (Manning's n, geometry changes, porosity, etc.), but none of them represent the real physics of the problem. This paper presents novel lab experiments that attempt to simulate LWD in a river channel. The experiments were developed in a straight research flume. The performance of the LWD in terms of outflow capacity and the effect in terms of increase in water levels upstream and velocities downstream have been analyzed. The orifice + weir model has been proposed as the more realistic model to simulate the flow through LWD, and empirical coefficients of discharge for applications in analytical methods and in numerical models have been obtained. The results help to understand the hydraulic behavior of LWD, and the coefficients of discharge obtained can be useful to reduce uncertainties in numerical modeling for practical applications.