Credit: City of Shoreline

Stormwater detention is an important part of urban infrastructure. It serves two main purposes: reduces or eliminates neighborhood flooding, and reduces contaminants entering larger bodies of water. City parks are playing an increasingly important role in dealing with stormwater.

Urban runoff from heavy rains has a deleterious effect on water quality in streams, rivers, and lakes, especially when sewage overflows become involved. And no one likes to have a flooded yard a few times a year. Or in an example of a worst case, Kate Fleming, a renowned audiobook narrator, was trapped and drowned in the basement of her Seattle home during the Hanukkah Eve Storm of 2006.

Building and maintaining underground tanks is one way to deal with large volumes of city runoff. But in recent years more emphasis is being placed on developing green stormwater systems, and city parks are often given the assignment.

Green stormwater systems come in a wide variety of designs and functionality. At a minimum, an open basin (natural or created) captures and retains rainwater flowing in from the surrounding neighborhood.

Sometimes the water is then sent on at a regulated rate to a treatment plant. But often the basin itself treats the water by allowing sediment to filter out naturally before the water flows into a creek or sewer drain. Some basins don’t even have outflows and the water simply evaporates.

A couple City of Seattle examples of the more natural type of stormwater detention systems are Meadowbrook Pond (a Seattle Public Utilities facility) and the Magnuson Park wetlands. Both are located in northeast Seattle.

The City Parks Blog (a national blog devoted to park issues) has been running a twenty part series on the City Parks, Clean Water report by The Trust for Public Land’s Center for City Park Excellence. The report examines the role of city parks in partnership with other city departments, and often third parties, in managing stormwater.

The fifth installment of the blog series features a Seattle area park, Cromwell Park in Shoreline. I scouted Cromwell Park for this blog last year, but it didn’t fit my criteria so I never wrote a preview. After the improvements is does make for a great neighborhood park though.

If you’d like to read about the park redesign, which included a small created wetland for stormwater detention, you can go to the blog post here.