National Stormwater Calculator
EPA’s National Stormwater Calculator (SWC) is a desktop application that estimates the annual amount of rainwater and frequency of runoff from a specific site anywhere in the United States (including Puerto Rico). Estimates are based on local soil conditions, land cover, and historic rainfall records.
It is designed to be used by anyone interested in reducing runoff from a property, including
- site developers,
- landscape architects,
- urban planners, and
The Calculator accesses several national databases that provide soil, topography, rainfall, and evaporation information for the chosen site.