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.
Boundary conditions allow one to constrain the physics along boundaries in the model. They are similar to initial conditions, which specify the model state at start time. As an example, at the walls of a bathtub, the flow normal to the walls is zero since they are impermeable. For general information on the topic, see the Wikipedia article. Note that the sea surface and sea floor (i.e. the top and bottom of the water mass) are also boundaries, though these are not addressed here. Since ADCIRC solves for water elevations and velocities (fluxes), typically some aspect(s) of these two quantities is what is constrained in a boundary condition.
For details on flux boundary conditions, see flux specified boundaries.