An extension of the above example is shown in Figure 9 where both sides of 
a breakwater are considered. The initial position of the shoreline and wave 
conditions in deep water are as before (Fig. 9). The boundary conditions 
become 
ox 
oY = O at x = -O (simplification of more exact condition) 
Oyen a 
— = -tana at x = +0 
ox 
The uniform depth theory of Penny and Price (1952) is used as an approxi- 
mation (not substantiated) for diffraction about the end of the breakwater. 
The shoreline is calculated for various multiples of a fixed At (Fig. 9,A). 
INCOMING WAVE 
DIRECTION 
\ INITIAL SHORELINE 
INCOMING WAVE INCOMING WAVE 
DIRECTION DIRECTION 
\ 
INITIAL SHORELINE 
Figure 9. Shorelines at successive times of SAt, 10At, and 15At (A); 
shorelines for time 2At (B) (vertical scale exaggerated). 
25 
