EPA SWMM

free (public domain) Design the Building

Free, public-domain stormwater, wastewater, and combined sewer system simulation model by the US Environmental Protection Agency -- dynamic hydrology-hydraulic-water quality simulation for single-event or continuous modeling of rainfall-runoff, pipe/channel routing, green infrastructure/LID controls, and pollutant loads; the industry-standard computational engine used worldwide for drainage design, CSO/SSO mitigation, floodplain mapping, and regulatory compliance (NPDES, CMOM, TMDL).

3.4 /5 composite score

Solid -- the free, public-domain industry-standard computational engine for stormwater/wastewater drainage modeling worldwide (FEMA-approved for NFIP studies), with an open-source C API and 50+ programmer toolkit functions enabling deep customization and integration; no subscription cost, a large active community (open SWMM, GitHub USEPA repo), and FEMA approval make it the de facto baseline for water infrastructure modeling; scoring reflects its outstanding value and openness despite a dated Windows-native GUI, no vendor support contract, and desktop-only delivery (no REST/CLI).

Solid

Rubric Scorecard

How we grade →

Criterion	Score	Evidence
Value for the price	5/5	free (public domain), from $0, free tier
Agent Friendliness	3/5	API: SWMM 5 Programmer's Toolkit (C API, DLL with 50+ functions for opening/modifying networks, running simulations, accessing results); open-source C engine on GitHub (USEPA/Stormwater-Management-Model)
Ease of adoption	2/5	desktop-install, steep learning curve
Portability & lock-in	5/5	4 file formats
Interoperability	2/5	5 integrations

Visit EPA SWMM →

How we verified this: we checked EPA SWMM against its live site and an independent source — en.wikipedia.org. Nothing on this page is listed from memory. See how we grade. Verified 2026-07-05.

Evidence

File formats

Format	Direction	Support
INP	native	full -- SWMM native .inp input format (industry-standard text format)
CSV	export	full
GIS	import	partial
DXF	export	full

Integrations

ArcGIS (middleware) QGIS (middleware) PCSWMM AutoCAD MicroStation

Adoption

Deploymentdesktop-install

Self-serve signupyes

Learning curvesteep

Pricing detail

Free tier scopeusable

Sources

Status Changelog

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