Local scour around submerged angled spur dikes under ice cover

Abstract

Local scour is a phenomenon leading to the localized lowering of the channel bed due to the imbalance of sediment transport. As spur dikes protrude into the natural channels, local scour could be triggered. Accurate estimation of local scour around spur dikes is crucial for the effectiveness of erosion control and prevention and habitat enhancement measures. In the current study, the correlations between the maximum scour depth and the overtopping ratio, spur dike dimensions, ice cover roughness, and grain size of the bed material are investigated. Under both open channel and ice-covered flow conditions, a variety of experiments were done in a large-scale outdoor flume with different experimental setups. The results revealed that the scour depths around submerged spur dikes increased with increases in the densimetric Froude number and the decreases in the overtopping ratio and alignment angle. The maximum scour depth around a submerged angled vertical wall spur dike is significantly affected by the presence of an ice cover on the water surface, namely, the rougher the cover, the deeper the scour hole. Based on data collected from the laboratory experiments, an existing maximum scour depth estimation equation has been modified to consider the influence of the cover condition and the submergence level. The calculated results showed high accuracy in estimation of the measured data.