More about HEC-HMS
You can install HEC-HMS v4.3 if you have 135.28 MB of free space on your hard drive; it can be named HEC-HMS Beta as well. Hydrologic Engineering Center provides this program for free. It is classified as belonging to the Education category, more precisely Science. Versions 4.2 and 4.1 are still the most popular ones and can be run on Windows 7/8/10/8.1. HEC-HMS.exe and hms.exe are the most popular installer names of the software you may come across. The direct download link was analysed by a number of antivirus solutions and was proved to be clean.

HEC-HMS is definitely a great software no doubt in that, but my company recently switched to GeoHECHMS by CivilGEO is kind of a data wrapper to the standard HEC-HMS software with some amazing features and capabilities. Hands down GeoHECHMS is by far one of the best stormwater modeling software that I've used.