... stormwater treatmentsystems—trees, meadows, wetlands, and other formsof soil and vegetation. For example, researchers at the University of California at Davis have estimatedthat for every 1,000 ... case-study cities.Among them were extent and duration of programefforts, availability of information and quantifiabledata, geographic location, and the number and typeof green infrastructure elements ... mostsuccessful at mitigating. About half of Portland’sland area is impervious, 25% attributable to streets, and 40% attributable to rooftops.54,55These surfacescreate an opportunity and a need for green...