APPENDIX 
COMPUTER PROGRAM 
This appendix presents the listing and brief explanation of the computer 
program written to investigate the behavior of a shoreline which contains a 
complete littoral barrier at x = 0. The numerical scheme is based on the 
finite-difference method of Crank-Nicolson, used to solve the cyclic nonlinear 
transport equations in Q and y. Although the program is written expressly 
for Holland Harbor, Michigan, hopefully, enough explanation is given to modify 
the program, if necessary, to suit a particular application. 
The program consists of a main program, which is simply a calling routine 
to the controlling subroutine, and eight subroutines. The interrelationship 
of these programs is shown in the figure below; a brief discussion of each 
subroutine follows. 
INPUTQ | 
f : 3 ; Sica 
Hy f 5 a i : 
i OREGION { smmems:| CALCKDQ fem ; SREGION | 
be . H & ts 2 
Venera f | e sea ee i hismesz es 
Figure. Program structure. 
MAINQ Calls subroutine EVOLVEQ 
EVOLVEQ The controlling subroutine which organizes the numerical method in a 
global sense and calls various other subroutines as required. The 
first call is to INPUTO, which reads the controlling parameters, his- 
torical shorelines and lake levels, and statistical wave information. 
For each month in the time period of interest, subroutine CALCKDQ is 
called. (It is assumed that during a month the diffraction coeffi- 
cients change negligibly.) For alternating equal incremental times 
the angle of the incoming waves is changed and subroutine SOLVEQ is 
called. This is repeated until a month's time has been completed. 
Then this is repeated until another historical shoreline is reached. 
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