For general information, see the ADCIRC site, ADCIRC FAQ, or the ADCIRC Wikipedia page. For model documentation not yet available on the wiki, see the ADCIRC site. New content is being continuously added to the ADCIRCWiki, and material from the main ADCIRC site will be gradually transitioned over to the wiki.
The fort.18 file is a file with information needed for parallel (MPI) execution of ADCIRC (commonly termed PADCIRC). The file is created by the adcprep executable, which is run prior to launching a parallel ADCIRC run.