usually faster than sieving. Sieving equipment is simple and generally 

 reliable whereas the settling tune and auxiliary electronic equipment are 

 complex and extremely delicate. For practical beach engineering problems, 

 sieve data are probably the most reliable and the most reproducible, espe- 

 cially among different laboratories. Therefore, if there is an option, 

 sieving data are preferable over settling data. It is also important that 

 the data from the two techniques ax*e not mixed because conversion equations 

 are not too powerful. 



III. SAMPLING 



1. Basic Considerations . 



The basic question concerning the design of a sediment sampling plan 

 for beach-fill purposes is "what are the composite grain- size characteris- 

 tics of both the native beach and the potential borrow sites? 1 " The sedi- 

 ment grain-size (textural) characteristics for the beach can be expected 

 to vary (a) across the beach profile through the varied energy zones, 

 (b) along the beach within any one energy zone, (c) at depth within the 

 sediment "envelope" on the active profile, and (d) between seasons within 

 the three-dimensional geometry of the beach. The composite gsd for the 

 beach should be a single-size distribution that reflects these four com- 

 ponents of textural variability; the approach would be to collect a suffi- 

 cient number of samples to accurately describe the "target" native beach 

 grain-size composite distribution. A similar approach to sampling would 

 be taken for characterizing the target borrow site composite. Many borrow 

 site areas are "relict" in the sense that the processes which originally 

 developed the geological characteristics of the sedimentary body are no 

 longer active. For example, several feet of modern fine sediments might 

 overlie an ancient shoal area containing relict coarse sediment. In this 

 case, the seasonal component of textural variation need not be considered 

 in the sampling scheme. 



2. Beach Sampling . 



Fixed rules for beach sampling will probably never exist because each 

 beach presents unique characteristics. General sampling guidelines can 

 be established, however, when sufficient data are available describing the 

 four components of textural variability. Although presently there are not 

 enough core samples to describe the depth component, these samples are 

 being collected. Some good data exist that describe the other three aam- 

 ponents of textural variation and the patterns from some of these data 

 will be discussed to set up suggested temporary sampling guidelines. 



Figure 4 summarizes several textural relationships common to most 

 beach data. Individual samples and various composite samples are compared 

 on this plot with a grand composite of 64 beach samples. Eight samples 

 were collected from each of four ranges at Pt. Mugu, California, in 

 November and May 1970; sample positions along the ranges were determined 

 by elevation. November is considered here to reflect the culmination of 

 "summer" conditions and May the "winter". The figure is constructed so 



\1 



