The US Environmental Protection Agency recently released their updated National Stormwater Calculator (SWC). The Calculator can be downloaded at: http://www.epa.gov/nrmrl/wswrd/wq/models/swc/. The SWC is a desktop application that estimates the annual amount of rainwater and frequency of runoff from a specific site. 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
- homeowners.
The Calculator accesses several national databases that provide soil, topography, rainfall, and evaporation information for the chosen site. The user supplies information about the site’s land cover and selects the types of low impact development (LID) controls they would like to use. The LID controls that the user can choose are the following seven green infrastructure practices:
1. Disconnection of gutters downspouts from storm drains
2. Rain harvesting
3. Rain gardens
4. Green roofs
5. Street planters
6. Infiltration basins
7. Porous pavement