Permeable surfaces in Seattle offer ideas on how cities can best deal with the environmental problems of urban runoff.
"We used to think that we should get that water out of sight as quickly as possible; rather than flooding streets, send it off to the bay lickety-split. But now we know that the gunk in that runoff causes problems for everyone, especially fish. Take copper, leaching from worn brake pad linings, roofing materials, algaecides, and fungicides. Copper can cause salmon to lose their sense of smell, so they aren't as alert to the presence of predators or able to find their natal stream. Some pesticides have the same effect."
"So how do we deal with stormwater? Rechanneling it into our aging sewer systems is not an option. The problem only gets worse as we add impervious surfaces with parking lots and new housing. A recent visit to Seattle convinced me that there is a better way."
"Using a revolutionary series of "natural drainage systems," Seattle is attempting to detain and slow stormwater by trying to mimic the forest floor and pasture that once covered its landscape. Bit by bit, the city rips out pavement and pipes in suburban and urban neighborhoods, replacing concrete and asphalt with swales, rain gardens, and other soft surfaces."
"Seattle's first project, called SEA Street (for Street Edge Alternative Street) was put in the ground in 2000 in an older neighborhood northwest of downtown. The city's transportation and public utilities departments worked with neighbors to replace an old 'unimproved' gutter and ditch stormwater system with a series of connected, vegetated swales. The swales resemble the understory of a Pacific Northwest forest. 'We're trying to make an urbanized environment think like it's still forested,' says Bob Spencer, the city's Creek Steward. The ground is soft and covered with leaf litter; trees and shrubs glisten in the damp air. Most of the vegetation is native, but some drought-tolerant non-natives are included; neighbors were given a range of choices. Looking at other streets nearby, I can see that SEA Street (aka 2nd Avenue NW between 120th and 119th streets), was previously an 'anywhere USA' older suburb. SEA Street now has a vivid sense of place, and songbirds and butterflies flit among the shrubs and trees."