explicit program version. The names of most key variables in the programs are 

 the same as those used in the main text of this report. They are again de- 

 fined here to make the explanation more self-contained. The programs them- 

 selves contain a large number of comment statements describing the operations 

 performed in distinct program segments. 



Programs YSEXP and YSIMP 



93. Lines 170-190 (150-170): These statements initialize basic pa- 

 rameters. YSBEG and YSEND define the beginning and end grid points of the 

 seawall (Figure 4), with YSBEG < YSEND. The grid spacing is DX (in meters) 

 and the time step is DT (in hours). NTIMES specifies the number of timesteps 

 and IT1 and IT2 denote timesteps when the wave data are changed in the exam- 

 ples. DENOM is the value of physical quantities in the denominator of Equa- 

 tion 2b, evaluated for quartz sand. K1 is the empirical coefficient (K) in 

 Equation 2b. The wave period is denoted by T (seconds). 



94. Lines 250-310 (240-290): Specify initial shoreline and seawall 

 positions for a straight beach and seawall. 



95. Lines 370-450 (350-430): Specify initial shoreline and seawall 

 positions for a curved beach and seawall. 



96. Line 570 (530): Call in wave data and renew as specified. 



97. Line 730 (680): Calculate closure depth, DCL0S, from wave 

 conditions. 



98. Lines 790-830 (780-810): These lines specify boundary conditions 

 for the simple cases of a fixed beach position and an impermeable long groin 

 (jetty, headland). 



99. Lines 850-960 (720-750): Calculation of the longshore transport 

 rate. 



100. Lines 1080-1150: In the implicit model, in order to make correc- 

 tions in both directions, a reversed double sweep is necessary. The longshore 

 transport rates in the arrays Q and QQ should be equal; a checking proce- 

 dure is provided to verify this. 



101. Lines 1270 (890): After the shoreline position is calculated, 

 each y^ must be checked to see if it violates the seawall constraint. The 

 subroutines C0RRI and C0RRE are called to do the check and to correct the 

 shoreline positions and transport rates as necessary. 



39 



