Sometimes structures must be provided to protect dunes, to maintain 

 a specific beach dimension, or to reduce nourishment requirements. In 

 each case, the cost of such structures must be weighed against the bene- 

 fits they would provide. Thus, measures to provide and keep a wider pro- 

 tective and recreational beach for a short section of an eroding shore 

 would require excessive nourishment without supplemental structures such 

 as groins to reduce the rate of loss of material from the widened beach. 

 A long, high terminal groin or jetty is frequently justified at the down- 

 drift end of a beach restoration project to reduce losses of fill into an 

 inlet and to stabilize the lip of the inlet. 



1.6 CONSERVATION OF SAND 



Experience and study have demonstrated that sand from dunes, beaches, 

 and nearshore areas is the best material available naturally in suitable 

 form to protect shores. Where sand is available in abundant quantities, 

 protective measures are greatly simplified and reduced in cost. When 

 dunes and broad, gently sloping beaches can no longer be provided, it is 

 necessary to resort to alternative structures, and the recreational attrac- 

 tion of the seashore is lost or greatly diminished. 



Sand is a diminishing natural resource. Sand was once available to 

 our shores in adequate supply from streams, rivers and glaciers, and by 

 coastal erosion. Now cultural development in the watershed areas and along 

 previously eroding shores has progressed to a stage where large areas of 

 our coast now receive little or no sand through natural geological pro- 

 cesses. Continued cultural development in both inland and shore areas 

 tends to further reduce coastal erosion with resulting reduction in sand 

 supply to the shore. It thus becomes apparent that sand must be conserved. 

 This does not mean local hoarding of beach sand at the expense of adjoin- 

 ing areas, but rather the elimination of wasteful practices and the pre- 

 vention of losses from the shore zone whenever feasible. 



Fortunately, nature has provided extensive stores of beach sand in 

 bays, lagoons, estuaries and offshore areas that can be used as a source 

 of beach and dune replenishment where the ecological balance will not be 

 disrupted. Massive dune deposits are also available at some locations, 

 though these must be used with caution to avoid exposing the area to flood 

 hazard. These sources are not always located in the proper places for 

 economic utilization, nor will they last forever. When they are gone, we 

 must face increasing costs for the preservation of our shores. Offshore 

 sand deposits will probably become the most important source in the future. 



Mechanical bypassing of sand at coastal inlets is one means of conser- 

 vation that will come into increasing practice. Mining of beach sand for 

 commercial purposes, formerly a common procedure, is rapidly being reduced 

 as coastal communities learn the need for regulating this practice. Modem 

 hopper dredges, used for channel maintenance in coastal inlets, are being 

 equipped with a pump-out capability so their loads can be discharged near 

 the shore instead of being dumped at sea. On the California coast, where 

 large volumes of sand are lost into deep submarine canyons near the shore. 



1-21 



