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Promoting Permeability
Lillie Simms, a 40-year resident of San Francisco’s Ingleside District, is fed up with looking out her front door onto a sea of small parking lots. Simms took the issue to Supervisor Geraldo Sandoval of District 11, who is initiating new legislation to discourage any more conversion of front yards to blacktop or concrete.
Besides addressing neighborhood aesthetics, Sandoval’s proposed ordinance could be important in reducing polluted stormwater runoff into San Francisco’s storm drain system and increasing aquifer recharge says Katie Pilat, hydrologist with the Neighborhood Parks Council. She points out that the Westside Basin aquifer, which runs from Golden Gate Park down to the San Francisco airport, has experienced rapidly declining water levels indicated by a 50% loss of Lake Merced’s water volume in the past 60 years.
"The remaining unpaved yards are some of the only conduits left where rainwater can enter the ground and replenish some of the water. Even small pieces of land can add up to capturing significant amounts of valuable rainwater," Pilat says. More and more San Francisco homeowners are paving their front yards as a solution to the city’s huge parking deficit. According to a recent article in The New York Times, San Francisco leads all other American cities in vehicles per square mile – 6,916 compared to New York City’s 5,500—and the number of registered vehicles in San Francisco outnumbers available public parking by 37,000 spaces. Add to that increased auto ownership per household region-wide and the expense of maintaining front yard greenery, and the decision to pave becomes even more tempting.
"We’re becoming an asphalt jungle," says Sandoval. "Two hundred years ago, San Francisco was covered with sand dunes, and there was an intensive effort to landscape the city. Now, much of that is being undone, slowly but surely, by property owners."
The current planning code states that at least 20% of a home’s front yard setback be appropriately planted. Many people, however, are unaware of the code or simply ignore it, according to Sandoval’s office. His proposal strengthens the code by requiring that homeowners maintain at that 20% landscaped area and prohibiting parking in the required "setback" space directly in front of the house. The S.F. Board of Supervisors is scheduled to vote on the ordinance in September.
Randy Hester, professor of landscape architecture at U.C. Berkeley, acknowledges that paving yards provides an immediate relief to the parking situation but warns of the tradeoffs. "Whether paving 20, 30 or 100 square feet, when that’s multiplied by 1,000 or even 10,000 homes, the amount and speed of water runoff are affected," he says. "When water enters the soil, the soil acts as a natural septic tank—whether it be sandy soil or loam, pollutants are removed. Getting more water to percolate in the soil rather than run off improves the quality of the water."
The Public Utilities Commission is supports Sandoval’s proposed legislation and is encouraging homeowners to landscape with drought-resistant, water-efficient native perennials and shrubs.
Contact: Geraldo Sandoval (415) 554-6975 RG
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