nourishment then maintains the shoreline at its restored position. When 

 conditions are suitable for artificial nourishment, long reaches of shore may 

 be protected at a cost relatively low compared to costs of other alternative 

 protective structures. An additional consideration is that the widened beach 

 may have additional benefits as a recreation feature. 



Under certain conditions, a properly designed groin system may improve a 

 protective beach. However, this method must be used with caution, for if a 

 beach is restored or widened by impounding the natural supply of littoral 

 material, a corresponding decrease in supply may occur in downdrift areas with 

 resultant expansion or transfer of the problem area. Detrimental effects 

 of groins can usually be minimized by placing artificial fill in suitable 

 quantity concurrently with groin construction to allow downdrift bypassing 

 of littoral material; such stockpiling is called filling the groins. Groin 

 construction should be sequential from fartherest downdrift to the most 

 updrift location within the system in order to achieve maximum natural filling 

 of the groin compartments. 



Groins may be included in a beach restoration project to reduce the rate 

 of loss and therefore the nourishment requirements. When groins are con- 

 sidered for use with artificial fill, their benefits should be carefully 

 evaluated to determine their justification. Such justification could be based 

 on the fact that groins will provide a greater reduction in the annual nour- 

 ishment costs than the increase annual charges for groin construction (see 

 Ch. 5, Sec. VI, 10). 



2. Limitations . 



The decision to use groins as part of a protective beach depends first on 

 the availability of suitable sand for the purpose, and if available, on the 

 cost per unit volume of fill and the cost of groin construction. Often the 

 cost per cubic meter of sand for small projects is quite high due to the 

 high expense of mobilizing and demobilizing the equipment needed for project 

 construction, whereas for larger fills the same expense constitutes a much 

 smaller proportion of the project funds. Also, artificial nourishment can be 

 quite costly per unit length of short shore segments because of the rapid 

 erosion of the widened beach which projects significantly seaward of the 

 adjacent shores to create a soft evodihle headland on which wave energy is 

 focused. The resulting high nourishment requirements may be justified for 

 short lengths of beach in cases where the artificial nourishment prevents the 

 enlargement of the problem area to downdrift shores. Difficulties may be 

 encountered in financing a shore protection method (in this case) which pro- 

 vides protection beyond the immediate problem area. The use of coarser than 

 natural, and consequently more stable, fill material in the original restora- 

 tion may reduce nourishment requirements, but may be less suitable as wildlife 

 habitat or for human recreation. The introduction of unnatural material may 

 also have other undesirable long-term effects to adjacent shorelines. A 

 sacrificial veneer of fine material over coarser, more protective material 

 would emulate natural conditions at some west coast and Hawaiian beaches. 



3. Planning Criteria . 



Planning of a protective beach by artificial nourishment requires the 

 following: 



5-7 



