Natural drainage in New Orleans and Portland

Stormwater management proposals that came out of a new urbanist charrette in the Gentilly section of New Orleans began to be acted upon in December — though not in Gentilly itself. Timberland, the outdoor shoe and clothing merchandiser, offered funds so that a local nonprofit organization, Groundwork New Orleans, could implement the natural drainage techniques in another part of New Orleans, Central City.

Groundwork New Orleans set about creating or improving “rain gardens” along nine blocks in Central City, to allow stormwater to filter into the ground. Bump-outs and some tree wells and planter strips between curb and sidewalk are being converted to rain gardens — slight depressions that reduce the volume of water going into storm sewers. Hard-packed clay soil is being replaced with a mixture of pea gravel, crushed limestone, soil, and compost. Turf is being replaced with plants that help infiltration.

Mary Vogel of PlanGreen collaborated with Tulane University adjunct professor Charles Reith, founder of Naturally Green Inc., and other professionals to design what Reith calls “the city’s first truly eco-functional landscape,” on the sides of streets and in neutral grounds (roadway medians) in Central City. Vogel participated in the Gentilly charrette led by Andres Duany that suggested those techniques.

Groundwork said those techniques have succeeded in cities such as Seattle, Washington, and Portland, Oregon. The Housing Authority of Portland, with a $35 million HUD HOPE VI seed grant, redeveloped the distressed 462-unit Columbia Villa public housing project in Portland into an 850-unit, ecologically advanced, mixed-income project that boasts new urbanist characteristics.

At New Columbia, as the HOPE VI project is called, “Ninety-eight percent of the stormwater is retained on-site,” says Marcy McInelly, president of Urbsworks, a Portland urban design firm that master-planned the redevelopment. “There is 80 percent less underground stormwater piping” than before, largely because of “green streets” that send much of their runoff into streetside swales, McInelly says. While improving the development’s ecology, Urbsworks also repaired the street grid, extensively connecting the 82-acre site to surrounding neighborhoods. Originally, says McInelly, “there were four roads in, four roads out.” Now all the existing streets on the project’s perimeter — 17 in all — extend through New Columbia. There is also a network of alleys. For more on New Columbia, click on