unlike power law curves reported to be appropriate (Keulegan and Krumbein, 

 1949; Bruin 1954, 1973; Dean, 1977; Bowen, 1980). In any case, determining 

 and interpreting a geometrical break on limit depth on usually small nearshore 

 slopes are not clear-cut tasks. 



(4) Summary on Seaward Limit Estimation . If a seaward limit estimate 

 is needed for planning engineering or research activities in a sandy coastal 

 region, the best office procedures is to adapt a proven seaward limit for a 

 like application in a similar locale. Modifications to take into account 

 somewhat different local conditions may be objectively based upon the profile 

 zonation outlined in Chapter 4, Section V,2,c,(2). This course seems 

 especially recommendable now that long-term hindcast wave data are becoming 

 available for U. S. coasts. 



If limited field study can be performed for the site of interest, it 

 appears worthwhile to concentrate on probing variations in nearshore sediment 

 characteristics, with interpretations as described in Section V,2,c,(l). All 

 available information should be considered in estimating the seaward limit to 

 significant onshore-offshore sediment transport. 



d. Beach Erosion and Recovery . 



(1) Beach Erosion . Beach profiles change frequently in response to 

 winds, waves, and tides. The most notable rapid rearrangement of a profile is 

 accomplished by storm waves, especially during storm surge (Ch. 3), which 

 enables the waves to attack higher elevations on the beach (see Fig. 1-8). 



The part of the beach washed by runup and runback is the beach face. 

 Under normal conditions, the beach face is contained within the foreshore, but 

 during storms the beach face is moved shoreward by the cutting action of the 

 waves on the profile. The waves during storms are steeper, and the runback of 

 each wave on the beach face carries away more sand than is brought to the 

 beach by the runup of the next wave. Thus the beach face migrates landward, 

 cutting a scarp into the berm (see Fig. 1-8). 



In mild storms, the storm surge and accompanying steep waves will subside 

 before the berm has been significantly eroded. In severe storms, or after a 

 series of moderate storms, the backshore may be completely eroded, after which 

 the waves will begin to erode the coastal dunes, cliffs, or mainland behind 

 the beach. 



The extent of storm erosion depends on the prestorm profile effects of any 

 shore-stabilizing structures or vegetation, wave conditions, storm surge, the 

 stage of the tide, and storm duration (see Table 4-6). Potential damage to 

 property behind the beach depends on all these factors and on the volume of 

 sand stored in the dune-beach-bar system when a storm occurs. 



For planning and design purposes, it is useful to know the magnitude of 

 beach erosion to be expected during severe storms. This type of information 

 is required for the volumetric design of beach nourishment; the required depth 

 of burial of ocean outfall and intake structures; and the functional design of 

 dunes, groins, jetties and revetments. Unfortunately, there is no satis- 

 factory procedure for accurately predicting expected storm losses. Moreover, 

 there is a general paucity of field data documenting the extreme events 



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