spread to adjacent shores, and the desired widening of the beach would 

 not be maintained. Here groins are necessary to stabilize the widened 

 beach within the limited reach. This justification by comparison of the 

 estimated annual costs with and without the groin system is therefore 

 irapracticablCo 



At the downdrift end of a beach, where it is desired to reduce losses 

 of material into an inlet and stabilize the lip of the inlet, a terminal 

 groin is used. Such a groin must often be justified by benefits from the 

 stabilized shore, as no other method of stabilization would be as suitable 

 and available for a comparative cost. Terminal groins should not be long 

 enough to perform the functions of jetties, but should impound only enough 

 littoral drift to stabilize the lip or edge of the inlet. 



5.611 LEGAL ASPECTS The legal considerations discussed previously under 

 Section 5.53 are applicable as well to the construction of groins. Legal 

 problems which arise are varied and often complex, due to the diversity of 

 legal precedent in different jurisdictions and the application of the 

 factual setting to a particular body of law. 



Previous sections covering the functional design of groins emphasize 

 the fact that adverse downdrift shore erosion can be expected if the up- 

 drift side of the groin is not artificially filled to its impounding ca- 

 pacity at the time of groin construction. Liability for property damage 

 insofar as the Federal Government is concerned will be determined with 

 reference to the Federal Tort Claims Act. 



It is therefore incumbent on the owner of groin-type structures to 

 recognize the legal implications of this coastal structure, and to plan, 

 design, construct and maintain the structure accordingly. It is thus 

 prudent to seek legal counsel at the earliest stages of formulation. 



5.7 JETTIES 



5.71 DEFINITION 



A jetty is a structure extending into the water to direct and con- 

 fine river or tidal flow into a channel, and to prevent or reduce the 

 shoaling of the channel by littoral material. Jetties located at the 

 entrance to a bay or river also serve to protect the entrance channel 

 from wave action and cross currents. When located at inlets through 

 barrier beaches, they also stabilize the inlet location. 



5.72 TYPES 



In the United States, jetties built on the open coast are generally 

 of rubble-mound construction. In the Great Lakes, jetties have also been 

 built of steel sheet-pile cells, caissons, and cribs using timber, steel, 

 or concrete. In sheltered areas, a single row of braced and tied Wake- 

 field timber piling and steel sheet piling have been used. 



5-46 



