Green Alleys: A New Paradigm for Stormwater Management

A program that installed green infrastructure in Los Angeles alleyways got its first real test last month as massive storms pummeled the region, bringing rain that overwhelmed much of Southern California’s stormwater infrastructure. As Alissa Walker writes in Curbed, thanks to the “green alleys” installed as part of a 2015 project in South Los Angeles, “the resulting stormwater had more opportunities to sink back into the earth: filtering through a row of permeable pavers, directing to pocket planters where creeping fig vines twirl up garage walls, or vanishing into grates labeled ‘drains to groundwater.’”

Walker explains that “a single green alley is able to capture enough stormwater per year to store it in dry wells below the pavers where it can slowly percolate into the groundwater, says Allen Compton, founder of the landscape architecture firm SALT, which designed these alleys.” The alleys connect to the South L.A. Wetlands Park, another key piece of green infrastructure that collects stormwater and provides habitat for local wildlife.

As storms become more intense and unpredictable, paved-over cities like Los Angeles can use permeable materials and sustainable design elements to capture and reclaim stormwater more effectively, recharge groundwater reserves, and prevent damaging floods. But “Because stormwater is still erroneously classified as a waste product, its management is handled by the same department that picks up the trash,” while other efforts are scattered across city and county agencies. According to Walker, Los Angeles is developing an interagency stormwater plan that would streamline and coordinate stormwater management efforts.