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EPA National Stormwater Calculator
StableEPA's free tool for estimating site runoff reduction from green infrastructure, with climate scenarios.
by US EPA
- Pricing
- Gov-Public
- License
- US Government (public domain)
- Commercial use
- Permitted
- Ecosystem
- SWMM
- Platform
- Web, Windows
About EPA National Stormwater Calculator
The National Stormwater Calculator estimates annual runoff, retention and frequency statistics for a site under different green-infrastructure choices — rain gardens, permeable pavement, cisterns, disconnection — using the SWMM engine underneath, US soils and rainfall data built in, and optional future-climate scenarios.
It targets the early planning conversation: what LID mix gets a site to a retention target, before anyone builds a full model. US-centric by data but conceptually portable, and its SWMM underpinnings mean results transfer credibly into detailed design.
Where it fits in the workflow
TerrainCatchmentRainfallRunoffRoutingHydraulicsMappingReporting
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