= 1 combined refraction and diffraction 

 Mote: Users should set this parameter to one. 



IGRID - Flag for indicating what type of grid system is 



being used (omitted) 



Note: This must be set to zero or omitted. 



83. The model can be run using either constant, or variably sized, 

 rectangular grid cells. This model documentation discusses only applications 

 involving grids with constant sized cells. As stated earlier, technology for 

 creating variable sized grids which are compatible with RCPWAVE does exist at 

 CERC. 



84. Bottom bathymetry for each grid cell must be supplied to the model. 

 The source code is written such that bathymetric data are read from the file 

 RCPDEPT in the following format. Depths along the entire row 1=1 (from J=1 



to J=N) are read using a 10F8.2 format. Depths along row 1=2 are read next, 

 and the procedure is repeated until depths along the offshore row I=M have 

 been read. An example of a bathymetric grid with 10 cells in the x-direction 

 (I coordinate) and 24 cells in the y-direction (J coordinate) is shown in 

 Figure 9. A depth file containing this data set, and written in 10F8.2 for- 

 mat, is also shown. It is a trivial matter to change this section of the 

 source code which reads the bathymetry (in subroutine DEPTH) to some other, 

 more convenient format. Such a modification will be illustrated later in this 

 section. 



85. The wave model considers only positive, nonzero water depths in its 

 computations. All grid cells which occupy dry land can be designated by nega- 

 tive depths or zeros in the input file, but the model will internally assign a 

 small water depth of 1.0 ft (or a metric equivalent) to each of these cells. 

 Depths in water cells that are less than 1.0 ft will be increased to this min- 

 imum value. Bathymetric input data are modified within the program in one 

 other way. Along each row, depths in columns J=1 and J=W are replaced by the 

 depths in columns J=2 and J=N-1, respectively. These changes are consistent 

 with the lateral boundary conditions used in the model. 



86. The third input file obtained by the JCL is the file RCPUPDT which 

 contains necessary or desired corrections to the source code via the "Update" 

 method. Figure 10 shows an example of an "Update" file. It is used to illus- 

 trate certain points pertaining to this correction method. The first state- 

 ment in the file 



48 



