Stormwater Impacts of Greening

Washington, DC (May 15, 2007)- Casey Trees recently released the results of a year long study modeling the stormwater impacts of greening scenarios, including enhanced tree canopy and the increased use of green roofs in the District of Columbia. Green roofs present a unique opportunity in DC because of the prevalence of high density town houses with flat roofs that could accommodate green roofs. Per unit area, green roofs intercept and store almost four times more rainwater than trees.


For an average year, the “Green Build-out” or high-end scenario prevented over 1.2 billion gallons of stormwater from entering the sewer system resulting in a reduction of 10 percent or over one billion gallons in discharge volumes to DC’s rivers and a 6.7 percent reduction in cumulative CSO frequency (74 discharges). The model also showed that the city could achieve up to a 54% reduction in stormwater runoff within several high volume sewersheds.
Related Resources:
Casey Trees
Green Bulid-out Model Full Report
Advisory Team Policy Recommendations
Data Display Tool
Mini-Model
Read Me Document for Data Display Tool and Mini-Model
2007 ASLA Award Winners