PART V: EXPLANATION OF COMPUTER PROGRAMS 

 General Comments 



88. Here, an explanation is given of main operations performed in four 

 of the five FORTRAN programs given in Appendix A. The programs are set up to 

 compute the examples presented in Part IV. The final shoreline positions cal- 

 culated in the examples are given in Part IV so that user implementations of 

 the programs can be checked. 



89. The programs constitute the foundation of a "1-line model" and cal- 

 culate shoreline change on a beach backed by a seawall by means of either the 

 explicit or the implicit numerical scheme. In order to run the programs for a 

 general case, wave information is needed to calculate the longshore sediment 

 transport along the beach in question. Specifically, the breaking wave height 

 and angle along the beach are required. The breaking wave field must be ob- 

 tained from a wave calculation program such as a refraction program or from a 

 combined refraction and diffraction program if large coastal structures are 

 involved. It was beyond the scope of this report to include a numerical wave 

 model. The breaking wave field will also be influenced by the plan shape of 

 the beach (the so-called sediment-wave interaction), which changes with time. 

 Numerical wave models and their relation to the shoreline change model are 

 discussed by Kraus (1983). 



90. The five subprograms are called by a main program. Input wave data 

 for the examples are fabricated in subroutine INDATA. The subroutine INDATA 

 is elementary and will not be discussed. The longshore sand transport rate, 

 computed by means of Equation 2, is calculated in subroutines YSEXP (explicit 

 solution scheme) and YSIMP (implicit solution scheme). Shoreline change in 

 the presence of a seawall is computed in subroutines CORRE (explicit) and 

 CORRI (implicit). These latter two routines correct both the transport rate 

 and shoreline position as described in Part III. 



91. Many of the algorithms are repeated in the subroutines. Comments 

 are given once for each generic type of algorithm. For clarity, the programs 

 are arranged to calculate for only one continuous seawall of arbitrary length 

 and configuration. They can easily be generalized to handle any number of 

 seawalls. 



92. In the explanations, the names of variables and line numbers refer 

 to those in the indicated programs. Line numbers in parentheses refer to the 



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