Space–time dynamics of local scour around submerged tandem and staggered piers in sand beds

Experimental studies on temporal variations around submerged piers on sand beds are compared here with the findings of an isolated pier under identical flows. Scour depths at the rear pier of the tandem case were found to decrease by 40% compared to the isolated pier. On the other hand, the scour depth around the staggered rear pier was similar to the isolated pier. From bed gradient computations, the mean of the highest gradients at deeper and upstream portions of the scour hole was approximately equal to the angle of repose in the isolated pier. The dynamic angle of repose increased by 20% and 40% in the front piers of the tandem and staggered arrangements respectively, vis-à-vis the isolated pier, leading to the rapid movement of sediments between the piers