Scour Problems at Piles or Other Vertical Supports 



21. For additional discussion of scour problems at and near piles, 

 consult Herbich et al. (1984) and Einstein and Weigel (1970). The problem 

 exists at piles because the structure causes the flow to accelerate as it 

 moves past the structure itself. In this case, vortices are usually generated 

 as the flow moves away from the obstruction, and it is the combination of 

 these effects which causes the sediment particles to become dislodged and 

 subsequently moved away from the structure. Research has shown, and it is 

 fairly obvious, that the greatest rates of scour occur where the fluid 

 velocity is greatest. Also, because the sediment slides down the upstream 

 slope and is deposited on the downstream slope, the walls of the scour hole 

 are typically at an angle roughly equal to the angle of repose (Figure 7) . 



Vertical Pile 



Figure 7. Scour problems at vertical piles 

 24 



