(3) Beach Profiles . Beach profiles extend from the foredunes, 

 cliffs, or mainland out to mean low water. Terminology applicable to features 

 of the beach profile is in Appendix A (especially Figs. A-1 and A-2) . The 

 backshore extends seaward to the foreshore and consists of one or more berms 

 at elevations above the reach of all but storm waves. Berm surfaces are 

 nearly flat and often slope landward at a slight downward angle (see Fig. A- 

 1). Berms are often bounded on the seaward side by a break in slope known as 

 the berm crest. 



The foreshore is that part of the beach extending from the highest ele- 

 vation reached by waves at normal high tide seaward to the ordinary low water 

 line. The foreshore is usually the steepest part of the beach profile. The 

 boundary betveen the backshore and the foreshore may be the crest of the 

 seawardmost berm, if a berm is well developed. The seaward edge of the fore- 

 shore is often marked by an abrupt step at low tide level. 



Seaward from the foreshore, there is usually a low tide terrace which is a 

 nearly horizontal surface at about mean low tide level (Shepard, 1950; Hayes, 

 1971a). The low tide terrace is commonly covered with sand ripples and other 

 minor bed forms, and may contain a large bar-and-trough system, which is a 

 landward-migrating sandbar (generally parallel to the shore) common in the 

 nearshore following storms. Seaward from the low tide terrace (seaward from 

 the foreshore, if the low tide terrace is absent) are the longshore troughs 

 and longshore bars. 



d. Profile Accuracy . Beach and nearshore profiles are the major sources 

 of data for engineering studies of beach changes; sometimes littoral transport 

 can be estimated from these profiles. Usually, beach and nearshore profiles 

 are measured at about the same time, but different techniques are needed for 

 their measurement. The nearshore profile is usually measured from a boat or 

 amphibious craft, using an echo sounder or leadline, or from a sea sled 

 (Kolessar and Reynolds, 1966; Reimnitz and Ross, 1971). Beach profiles are 

 usually surveyed by standard leveling and taping techniques. 



The accuracy of profile data is affected by four types of error: sounding 

 error, spacing error, closure error, and error due to temporal fluctuations in 

 the sea bottom. These errors are more significant for nearshore profiles than 

 for beach profiles. 



Saville and Caldwell (1953) discuss sounding and spacing errors. Sounding 

 error is the difference between the measured depth and the actual depth. 

 Under ideal conditions, average sonic sounding error may be as little as 0.03 

 meter (0.1 foot), and average leadline sounding error may be about twice the 

 sonic sounding error (Saville and Caldwell, 1953). (This suggests that sonic 

 sounding error may actually be less than elevation changes caused by transient 

 features like ripples. Experience with successive soundings in the nearshore 

 zone indicates that errors in practice may approach 0.15 meter (0.5 foot).) 

 Sounding errors are usually random and tend to average out when used in volume 

 computations, unless a systematic error due to the echo sounder or tide 

 correction is involved. Long-period water level fluctuations affect sounding 

 accuracy by changing the water level during the survey. At Santa Cruz, 

 California, the accuracy of hydrographic surveys ivas ± 0.45 meter (1.5 feet) 

 due to this effect (Magoon and Sarlin, 1970). 



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