SEAWARD LIMIT OF SIGNIFICANT SAND TRANSPORT BY WAVES: 

 AN ANNUAL ZONATION FOR SEASONAL PROFILES 



by 

 Robert J. Eallermeiev 



I . INTRODUCTION 



Certain coastal activities require consideration of the seaward limit to 

 significant wave-induced bed activity along a sand beach profile. Examples in- 

 clude design of nearshore structures, subaqueous beach fill, and borrow or 

 disposal of material. The seaward limit to significant sand movement by waves 

 clearly depends on both wave and sand characteristics through the mechanisms of 

 wave agitation of sand. However, available guidelines on the seaward limit 

 (U.S. Army, Corps of Engineers, Coastal Engineering Research Center, 1977, pp. 

 4-63 to 4-70) proceed from indirect or qualitative consideration of wave-sand 

 interactions. This report provides a new quantitative procedure for seaward- 

 limit estimation based on definite wave-sand interactions. A comprehensive 

 discussion of the present procedure and of other seaward-limit treatments is 

 provided in Hallermeier (1981). 



The present procedure defines an annual beach profile zonation related to 

 the seaward limit. Figure 1 is a schematic illustration of this zonation and 

 identifies the terminology used here. The water depths d^ and d^, respec- 

 tively the landward and seaward bounds of the shoal zone, are calculated in 

 Section II, using sand characteristics and statistics of annual wave climate 

 for a given locality. This shoal zone is a buffer area where expected waves 

 have neither strong nor negligible effects on the sand bed during a typical 

 annual cycle of wave action, according to available knowledge of sand movement 

 by v/aves . 



The water depth, d^ , gives a seaward limit to extreme surf-related effects, 

 so that significant alongshore transport and intense onshore-offshore transport 

 are restricted to water depths less than d^ . The water depth, d-, gives a 

 seaward limit to sand motion by usual waves, so that significant onshore-offshore 

 transport is restricted to water depths less than d-j^. The seaward limit in 

 sandy regions reasonably falls within this calculated shoal zone, although place- 

 ment of the limit depends on the particular engineering application, as pointed 

 out in Section III. 



'Tidal Ronge ^^ Seosonol 



j^ .-, -- •' _ \ Ronge ol 



Mean Sea Level — I - ■ "L-^-^-t:!—! Sond Level 



-Meon Sand Level 



OFFSHORE ^ \ ^ SKOAL w j^ LITTORAL 



ZONE "^^ ZONE ^^^^ ZONE 



Figure 1. Definition sketch of annual sand beach zonation and terminology. 



