We are pleased to present an article by environmental attorney Keith Scully on how Urban Stormwater issues relate to increased Density. Keith has a successful track record
Stand in any urban parking lot during a rainstorm and chances are you’ll be able to watch a slow stream of oil float past. That oil, in most of the region, flows untreated into either storm drains or natural watercourses, and from there to the Puget Sound or our lakes. The oil is not alone; also carried in stormwater are a toxic brew of pesticides, fertilizers, rubber from tires, and the other pollutants we all produce. During high rain events, in many parts of the region, combined sewers mean that raw sewage joins the mix, in a highly diluted form. The way we build our cities and coordinate density in our region has a profound effect on the level of pollutants, but finding the perfect density match is a challenge.
Recently, conventional wisdom on urban density’s impact on stormwater has shifted. The former method was to keep density low to protect ground and surface water, on a theory that the increased permeable surfaces (lawns, gardens, trees) of low-density development served as a natural filter. But long-term studies have demonstrated that by spreading development out, we get more impervious surface overall, and water quality in the region suffers. Houses on quarter-acre lots, for example, have longer impervious driveways, more outbuildings, and are more auto-dependent than townhouses. Further, a house built in a forested or wetland area not only adds impervious surface but also removes the trees we need to absorb and filter rainwater. This new thinking – that urban density is a good thing for stormwater management – has captivated the land use and environmental communities. Search the web for articles on density and water protection, and you’ll be hard pressed to find anything other than advocacy for the densest cities possible.
But a balance has to be struck. While dense urban communities aid stormwater management by leaving the countryside alone, they also concentrate pollutants. Without adequate stormwater controls in the urban areas, simply forcing everyone to live there is a marginal benefit, if it is a benefit at all.
Urban management of stormwater is a thorny problem – and one that requires significant open and naturally vegetated space in our cities, reducing the density our urban areas can absorb. Most agree that the best approach to urban stormwater management is to combine treatment facilities - making sure that as much of the stormwater as possible goes through mechanical and biological filtration to remove toxins – with natural prevention in the form of increased permeable surfaces, so water soaks into the ground rather than runs off, and natural filters like vegetation, ponds, and swales. Treatment facilities cost money. Natural prevention requires land.
Further, not all of us are going to live in highrises. Plus, despite the best efforts of urban planners, most of us choose to keep our cars, even when we do live in a dense environment. Regions thus have to accept both that some lower-density development has to be part of regional planning, and that creating superdense urban communities will involve serious investments in stormwater infrastructure, as well as the will to leave enough open space for the parks, bioswales next to roadways, and wetlands we need to ensure that we aren’t simply concentrating our pollution problems.
The tools available to municipalities for managing stormwater vary from the indirect, such as controlling density through the comprehensive plan and zoning regulations and ensuring that there is adequate forested parks and open space, to the direct, such as either building stormwater detention ponds and other flow control or filtration measures with tax dollars, or mandating that new development include them. There is no single solution to stormwater management, and the shift in municipal thinking needs to be to evaluate stormwater in every land use decision. At the very least, municipalities should have a comprehensive stormwater management plan, with both design minimums for private construction and plans and priorities for municipal expenditures.
Keith Scully is an environmental and land use attorney with Gendler & Mann LLP. He has formerly worked as the Legal Director of Futurewise, where he litigated Growth Management Act, Shoreline Management Act, and SEPA appeals to all levels of the Washington State court system and Growth Boards. He has also prosecuted war criminals for the United Nations, and served as a Deputy Prosecuting Attorney for King County, where he focused his career on appeals and complex crimes. He is on the Board of Directors of King County Conservation Voters, and tries to put his lifestyle where his mouth is by living close to work and bicycling, but admits that he has yet to give up his car . . .
Photo Credits - Local Flooding, by Janet Way, Keith Scully, Gendler/Mann