native sand are selected for the comparison because they result from the 

 selective winnowing and distribution of sediment across the active profile by 

 shoreface processes; their distribution reflects a state of dynamic equilib- 

 rium between sediments and processes within the system. See Hobson (1977) and 

 Hands and Hansen (in preparation, 1985) for specific sampling guidelines, a 

 discussion of composite samples, and a determination of offshore limits for 

 sampling. 



c. Sel ecti on of Borrow Mate rial. After the characteristics of the native 

 sand and the longshore transport processes in the area are determined, the 

 next step is to select borrow material for beach fill and for periodic nour- 

 ishment. As explained in the previous paragraph, an average native texture, 

 called the native composite , is used to evaluate the suitability of potential 

 borrow sand because the native textural patterns are assumed to be the direct 

 response of sand sorting by natural processes. Simply stated, it is assumed 

 that these same processes will redistribute borrow sand that is placed on the 

 beach in a similar textural pattern as the native sand along the profile 

 considering the differences between native and borrow sand texture. Sorting 

 and winnowing action by waves, tides, and currents will therefore tend to 

 generally transport finer sizes seaward, leave the coarsest sizes slightly 

 shoreward of the plunge point, and cover the beach face and remaining offshore 

 areas with the more medium sand sizes. Some sediment sizes that are in borrow 

 material and not in the native beach sand may not be stable in the beach 

 environment. Extremely fine particle sizes are expected ultimately to be 

 moved offshore and lost from the active littoral zone while fragile grains, 

 such as some shells, will be broken, abraded and possibly lost. These kinds 

 of changes to the borrow sediment will, through time, make the texture of the 

 beach fill more like the original native sediment but will, in the process, 

 reduce the original volume of fill placed on the beach. 



Borrow sediments containing organic material or large amounts of the finer 

 sand fractions may be used as beach fill since natural sorting and winnowing 

 processes can be expected to clean the fill material. This has been con- 

 firmed with fills containing foreign matter at Anaheim Bay and Imperial Beach, 

 California, and Palm Beach, Florida. Also fill material darkened by organic 

 material (Surf side/ Sunset Beach, California) or "reddened" by oxidized clay 

 minerals (Imperial Beach, California) will be bleached quickly by the sun to 

 achieve a more natural beach color. Material finer than that exposed on the 

 natural beach face will, if exposed on the surface during a storm, move to a 

 depth compatible with its size to form nearshore slopes flatter than normal 

 slopes before placement. Fill coarser than the sand on the natural beach 

 will tend to remain on the foreshore and may be expected to produce a steeper 

 beach. However, coarser material moved offshore during storms may not be 

 returned to the beach during poststorm periods. The relationship between 

 grain size and slope is discussed in Chapter 4, Section V,2,f. If borrow sand 

 is very coarse, it will probably be stable under normal as well as more severe 

 conditions, but it may make the beach less desirable for recreational use or 

 as wildlife habitat. If the borrow material is much finer than the native 

 beach material, large amounts will move offshore and be lost from the beach. 

 Angularity and mineral content of the borrow material may also prove important 

 factors in its redistribution, deflation, and the esthetic qualities of the 

 beach. 



5-9 



