Mom S«« Lo«l 



Figure 8. Scour problems at vertical seawalls 



period of time, the foundation of the wall is removed and the structure 

 collapses from its own weight. To combat this, stone aprons often are used to 

 harden the toes against scour and help preserve the foundation. 



Scour Problems at Submerged Pipelines 



25. Another situation where scour presents a problem for coastal 

 engineers and oceanographers is the case of scour under and around submerged 

 pipelines. For additional discussion of this problem, consult Herbich et al. 

 (1984) and Hales (1980). Scour around pipelines occurs in much the same 

 fashion as with pilings in that the flow is accelerated as it moves around and 

 over the structure. This increased velocity, and eddies which accompany it, 

 result in localized areas of scour that expose portions of the pipeline, which 

 in turn leads to other problems , including attachment by barnacles (which 

 increases the surface area exposed to flow as well as increasing drag, 

 exposure to increased flow forces, and loss of protection afforded by the 

 sediment that originally covered it. In the majority of these cases, the ■ 

 problem results from improper installation of the pipe. Most often the pipe 

 is not buried to design depths or is not buried at all. When this is the 

 case, scour holes will usually develop and expose the pipeline to the damage 

 mechanisms previously mentioned (Figure 9) . 



Figure 9. Scour problems at pipelines 

 26 



