where 



Dijq = median particle diameter 



H = maximum wave height in the spectrum (equal 

 to twice the significant wave height) 



T = wave period 



The third zone is the transition area seaward of the D-profile and landward of 

 the point where sediment motion is initiated by wave action. Bed -load trans- 

 port is normally the only transport in this zone. The point dividing the 

 lower limit of the D-profile and the upper limit of the transition area was 

 determined empirically by Swart, and the depth of this point is given by the 

 following equation: 



4.347 H°' A73 



I T 0.894 °0.09 3 'I 

 50 



where A is the deepwater wave length and H is the deepwater wave height. 



76. The basic assumption in the theory of Swart is that the D-profile 

 will eventually re'ach a stable situation under constant wave attack. This 

 stable situation implies both an equilibrium form and position of the beach 

 profile. By considering many small- and full-scale tests of profile develop- 

 ment under wave attack, Swart was able to develop equations that determine the 

 form and position of the equilibrium profile for different incident wave 

 climates. 



77. At every location "i" on the D-profile, Swart defines an onshore 

 and offshore segment of the profile (Figure 24). The length of the onshore 

 profile is represented schematically by the distance L-, . and the length of 

 the offshore profile by I^j . The length difference at each point i be- 

 tween the onshore and offshore sections of the D-profile, (L? - L-^)^ , is the 

 key parameter used by Swart to characterize a profile. The value of this 

 parameter when the profile is in equilibrium is defined as W? . Swart thus 

 represents the equilibrium profile by a "W-curve". He defines the W^ value 

 at the still-water line as W which is given by the following equation: 



57 



