If the deposition basin in the lee o£ an offshore breakwater is not 

 cleared of accumulations regularly, it is possible that continuing accre- 

 tion may ultimately produce land from the former shoreline out to the 

 breakwater. Resumption of bypassing operations may then require ownership 

 determination. 



Legal considerations may even arise on the downdrift beach receiving 

 bypassed sand despite the obvious advantages to most property owners. 

 Another case involved a pier used for fishing, located on a beach that had 

 been artificially nourished. Before this work was commenced, water of 

 adequate depth existed for fishing, but after beach nourishment was 

 commenced, depths decreased along the pier to such an extent that fishing 

 was greatly impaired. The owner then brought suit seeking payment for the 

 loss of value to his pier. 



It is not the purpose here to set forth a comprehensive discussion of 

 the legal problems encountered in connection with sand bypassing. The 

 above discussion is merely to alert the planner that such problems do 

 arise, and it is therefore prudent to seek legal counsel at the earliest 

 stages of project formulation. 



5.6 GROINS 



5o61 INTRODUCTION 



The groin is probably the type of structure most widely used for 

 shore protection purposes; yet the detailed operation of the groin is 

 poorly understood. Groins or groin systems in many locations have 

 achieved the intended purpose. In other locations, only negligible 

 benefits have resulted, or damaging recession of the downdrift shore- 

 line has been caused, even when groins were apparently successful in 

 accomplishing the design objective. Failures can be traced to a lack 

 of understanding of the functional design of groins and the littoral pro- 

 cesses to which the structures are subjected. 



5.62 DEFINITION 



A groin is a shore protection structure designed to build a pro- 

 tective beach or to retard erosion of an existing or restored beach by 

 trapping littoral drift. Groins are usually perpendicular to the shore 

 and extend from a point landward of predicted shoreline recession into 

 the water far enough to accomplish their purpose. Groins are narrow, 

 and vary in length from less than 100 feet to several hundred feet. Since 

 most of the littoral drift moves in the zone landward of the normal breaker 

 zone (for example about the 6-foot contour on the Atlantic coast), extend- 

 ing a groin seaward of that depth is generally uneconomical. The normal 

 breaker zone for the Gulf coast and less exposed shores of the Great Lakes 

 ranges from 3- to 4-foot depths; more exposed shores of the Great Lakes 

 approach the 6-foot depth. The Pacific coast ranges from 7- to 10-foot 

 depths depending on exposiire. 



5-31 



