less, it becomes impracticable to maintain the increased width by artificial 

 nourishment of that beach alone. The nourishment material would rapidly 

 spread to adjacent shores, and the desired widening of the beach would not 

 be maintained. Here groins would be necessary to stabilize the widened 

 beach within the limited reach. Choosing an alternative by comparison of the 

 estimated annual costs with and without the groin system would therefore be 

 impracticable . 



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 

 should be used. Rarely would any other method of stabilization be as suitable 

 and available at a comparative cost. A terminal groin should not be long 

 enough to function as a jetty; the groin should impound only enough littoral 

 drift to stabilize the lip or edge of the inlet. 



The legal considerations discussed previously in Section V,3 of this 

 chapter are also applicable to the construction of groins. Legal problems 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 information on the functional design of groins emphasizes the 

 fact that adverse downdrift shore erosion can be expected if the updrift side 

 of the groin is not artificially filled to its impounding capacity 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 in order to 

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

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



VII. JETTIES 



1 . Defi n itio n. 



A jetty is a structure that extends into the water to direct and confine 

 river or tidal flow into a channel and 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, jetties also 

 stabilize the inlet location. 



2 . Types. 



In the coastal United States, jetties that have been 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, single rows of braced and 

 tied Wakefield timber piling and steel sheet piling have been used. 



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