The Runoff Reduction Method was developed in order to promote better stormwater design and as a tool for
compliance to meet new stormwater runoff volume reduction requirements in the United States.
Runoff reduction has benefits beyond pollutant load reductions. BMPs that reduce runoff volumes can do a
better job of replicating predevelopment hydrologic conditions, protecting downstream channels, recharging
groundwater, and, in some cases, reducing overbank (or “nuisance”) flooding conditions.
When utilizing runoff reduction stormwater practices the designer experiments with combinations of several
runoff reduction practices (BMPs) on the site. In each case, the designer estimates the area to be treated
by each runoff reduction practice to incrementally reduce the required treatment volume for the site. The
designer is encouraged to use runoff reduction practices in series within individual drainage areas (such as
rooftop disconnection to a grass swale to a bioretention area) in order to achieve a higher level of runoff
West Virginia's spreadsheet tool works very well in determining the amount of runoff volume to capture in
order to meet the provisions of the MS4 permit.