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There’s no substitute for open, undeveloped land to filter pollutants out of runoff. If a city can’t restore large tract of its land back to a pristine state, it can mimic the environmental cleansers in architectural design.

Thirty percent of all nitrate and phosphorous pollution settles on the roof in the form of particulate matter. Within one hour of a storm, most of these pollutants and toxins enter the groundwater. According to Paul Kephart of Carmel Valley’s Rana Creek Habitat Restoraton and Living Architecture, a green roof like the ones he designs and constructs can absorb and purify 70 percent of that rainfall.

Integrated with bioswales and other elements of living architecture, a building can capture and cleanse 100 percent of its stormwater. Today, thanks to Kephart, structures like Casa Feliz—a 59-unit low income housing development on Main Street in San Jose—and the nearby police station capture 100 percent of their stormwater.

Developers like Casa Feliz’s First Community Housing are discovering that green roofs only increase the project’s total cost by one-half to one percent and actually cost less long-term than installing off-site stormwater-management improvements that would be required otherwise.

Of further interest to our drought-prone area is the fact that many of Kephart’s designs re-use what they capture. The grandest example is the Vancouver Convention Center, which provides 3 million more gallons of water than it even needs from its 6.5-acre living roof.

Plus, there’s no need to completely rebuild our communities. Elements of living architecture can be incorporated into existing structures. Some simple LID techniques include biorentention cells or rain gardens, strategically placed depressions that contain soil amendments which promote the absorption of stormwater; amended soil, soil enriched with sand and organic materials to increase its capacity to filter water; porous pavement, concrete that allows rain to infiltrate, thereby reducing runoff; and replacing hardscape with grassy swales, preserved native vegetation and natural drainage in mind.