Local Scour Associated with Angled Spur Dikes

A series of experiments were conducted in which the volume of the scour hole associated with model spur dikes was measured in a laboratory flume under clear-water overtopping flows. Spur dike models were angled at 45, 90, and 135° to the downstream channel sidewall with contraction ratios of 0.125 and 0.250. The main goals of the experiments were to evaluate the effect of the three angles on the volume of scour and potential aquatic habitat and on minimizing erosion adjacent to the streambanks. The experiments showed that of the three angles tested, the least erosion of the bed in the near bank region was associated with the spur dikes with 90° angles, while the greatest volume of the scour hole was associated with the 135° spur dikes. It was concluded that spur dikes with 135° angles showed the best potential for providing improved aquatic habitats while minimizing the potential for erosion of the channel bank.