National Stormwater Calculator

This tool estimates the annual amount of rainwater and frequency of runoff from a specific site using green infrastructure as low impact development controls. 

Estimates are based on local soil conditions, land cover, and historic rainfall records. A climate change component is included to help users explore how climate change impacts may affect the amount of stormwater runoff produced by a site, and how it is managed. 

Green infrastructure promotes the natural movement of water, instead of allowing it to wash into streets and down storm drains. The Calculator also allows users to consider how runoff may vary based on historical weather and potential future climate.