HydroCAD combines the best of TR-20, TR-55, and SBUH, plus built-in hydraulics, graphics, automatic database, and on-screen routing diagram in a single program. (see comparison table) The result is the fastest, easiest, and most capable stormwater modeling system available. We call it HydroCAD because it brings the benefits of Computer Aided Design to hydrology, while not requiring any other CAD software. However, HydroCAD-10 now offers direct extraction of subarea data directly from AutoCAD®, without any other software.