Flow discharge coefficient of crest weirs with covered vegetation

Abstract

The flow data of mountainous rivers is very important in hydrological forecasting. Crest weirs with smooth surface have been widely used and studied, while there is little information on the weir covered with vegetation. In this experiment, the flow coefficient reduction are systematically investigated by different density flexible artificial vegetation, in addition to the changes of discharge, crest length and height. The equivalent roughness height of vegetation on the weir was calculated. It was found that the flow coefficient with vegetation is smaller than smooth crest. According to the ratio of upstream water head to the length of vegetation weir crest, the experimental flow can be divided into broad-crested weir flow rate of H/L < 0.4 and narrow-crested weir flow rate of H/L > 0.4. The flow coefficient reduction rate of both types of weir flow rates varies to a certain extent. Experimental data showed that the crest weir height H/P played a different law for the broad-crested weir and narrow-crested weir. Taking into account the influence of vegetation, crest length and height, empirical formula for flow coefficient was proposed for flow estimation correction.