Causeway Flow
Commercial
Storm and foul water drainage design and 1D hydraulic modelling software for UK and Irish civil engineers.
EPA SWMM
DHS VerifiedActiveThe public-domain engine of urban drainage: dynamic-wave pipe networks, runoff, LID and water quality.
by US EPA
- Pricing
- Gov-Public
- License
- Public domain (CC0)
- Commercial use
- Permitted
- Ecosystem
- Standalone, C engine, Python ecosystem
- Platform
- Windows, Linux (engine), macOS (engine)
About EPA SWMM
EPA's Storm Water Management Model is the reference engine for urban hydrology and hydraulics: subcatchment rainfall-runoff, full dynamic-wave routing through pipes, channels, storage and controls, low-impact-development modules, groundwater interaction, and pollutant buildup-washoff — continuous or single-event.
SWMM's public-domain status is why the entire urban-drainage software industry sits on top of it: PCSWMM, InfoWorks-style suites, countless municipal spreadsheets and the whole PySWMM ecosystem. Learn the engine once and every wrapper becomes familiar. If you do urban drainage and have not opened SWMM directly, it is worth knowing exactly what the commercial GUIs are charging for.
Where it fits in the workflow
TerrainCatchmentRainfallRunoffRoutingHydraulicsMappingReporting
Appears in collections
- The Free Drainage Engineer's Toolkit
Zero-budget, reviewer-accepted tools for everyday stormwater and drainage design.
- The SWMM Ecosystem
The public-domain urban drainage engine and everything that grew around it.
Alternatives to EPA SWMM
Ranked by the topics, categories and workflow stages they share with EPA SWMM.
LocalSWMM
Open Source
Browser-based urban stormwater and drainage modeling powered by OpenSWMM 6 compiled to WebAssembly.
Visual OTTHYMO
Commercial
Hydrologic modeling software for urban and rural stormwater management, master drainage planning, and pond design.
PCSWMM
Commercial
CHI's commercial GIS front-end for SWMM — the most direct productivity upgrade for serious SWMM users.
Delta Hydro Studio
FreemiumVerified
Browser-based hydrology and hydraulics calculators for practising engineers — no install, report-ready output.
NetSTORM
Free
CDM Smith's free rainfall statistics and STORM-method screening model — IDF analysis, disaggregation, CSO planning.