The United States Environmental Protection Agencies (USEPA's) Storm Water Management Model (SWMM)
is a comprehensive computer model for analysis of quantity and
quality problems associated with urban runoff. Both single-event and continuous simulation
can be performed on catchments having storm sewers, or combined sewers and natural
drainage, for prediction of flows, stages and pollutant concentrations. Extran Block
solves complete dynamic flow routing equations (St. Venant equations) for accurate
simulation of backwater, looped connections, surcharging, and pressure flow.
Modeler can simulate all aspects of the urban hydrologic and quality cycles, including rainfall, snowmelt, surface and subsurface runoff, flow routing through drainage network, storage and treatment. Statistical analyses can be performed on long-term precipitation data and on output from continuous simulation. SWMM can be used for planning and design. Planning mode is used for an overall assessment of urban runoff problem or proposed abatement options.
SWMM is a dynamic rainfall-runoff simulation model, primarily but not exclusively for urban areas, for single-event or long-term (continuous) simulation. Flow routing is performed for surface and sub-surface conveyance and groundwater systems, including the option of fully dynamic hydraulic routing in the Extran Block. Nonpoint source runoff quality and routing may also be simulated, as well as storage, treatment and other best management practices (BMPs). Version 4.3 (May 1994) contains corrections and enhancements to Version 4.20 (June 1992), including a new Transport flow divider, revised hydraulic radius calculations for natural channels in Extran and Transport (to agree with the HEC-2 method), multiple land use options in Runoff, additional sewer infiltration options, improved manipulation of long-term rainfall data (especially 15-min data), a linkage to WASP4 from Transport, additional statistical output from Runoff and many other corrections and enhancements to various program options. Version 4.4 contains many more improvements and options and modifications. Version 4.4 is the recommended version for all users.
The executable program and the Fortran code may be downloaded from this Web site (see later instructions), and this is the recommendation in order to have the most recent code changes. The 1994 version 4.3 is also available from the EPA CEAM. The OSU code and EPA CEAM code is DOS-based and runs in a window under Windows 95/98/NT/2000. Although it will run under DOS with a 486 processor, a Pentium is recommended. Program storage requires about 5 Mb of hard disk space. Also included with the OSU and EPA releases is the Fortran source code, program documentation (but not the users manuals), and several sample input files. See this and the EPA CEAM Web site for details.
State-of-the-art graphical user interfaces are available from third-party venders listed later in this Web site. Most of these GUIs are constructed around the core Fortran code of the OSU model version.