Our software library provides a free download of SWMM 5.0.022 for Mac. SWMM for Mac is included in Design & Photo Tools. The current installation package available for download occupies 81.5 MB on disk. Our antivirus scan shows that this Mac download is malware free. This free Mac application was originally developed by Steffen Macke.
From the developer:
The EPA SWMM (Storm Water Management Model) is an app that can be used to design and analyze sewage networks. The program is a dynamic rainfall-runoff-subsurface runoff simulation model used for single-event to long-term (continuous) simulation of the surface/subsurface hydrology quantity and quality from primarily urban/suburban area.
You may want to check out more software for Mac, such as Adobe Flash CS4 Professional, eBPMN or pressSIGN 4, which might be similar to SWMM.