THE BLOG
11/14/2014 09:12 am ET Updated Jan 14, 2015

Protecting Watersheds As We Grow Our Cities and Towns

We don't have to choose between a growing population and healthy economy, on the one hand, and a healthy and sustainable environment, on the other. We really can have it both ways.

But we need to be smart about it. I'm particularly interested in smart strategies that deliver greener, healthier cities and towns while allowing them to grow. In an earlier article, I wrote about how smart land use planning can help reduce greenhouse gas emissions that cause global warming. It turns out that some of the same strategies can help clean our waterways as well.

In particular, in parts of watersheds that remain rural or natural, we need to curb the spread of suburban sprawl, which inevitably brings with it more impervious surface in the form of roads, streets, parking lots, and rooftops. Impervious surface, in turn, in turn prevents rainwater and other precipitation from soaking into the ground and, instead, causes it to run off, picking up volume and pollutants along the way to receiving waters. In many urban areas, polluted runoff is the greatest cause of dirty water.

In parts of watersheds that are already developed - which, by the way, are where we want as much future growth to go as possible - we need to undertake remedial measures such as strategically designed tree plantings, native landscaping, green roofs, rain gardens, rain barrels and other "green infrastructure" that can capture precipitation and filter it gradually into the ground instead of allowing it to become polluted runoff.

In both cases - preserving undeveloped landscapes outside of cities while we bring more greenery into them - we are taking advantage of the functions of nature along with its beauty.

These principles are explicitly recognized in a new report from the Potomac River Conservancy titled River Friendly Growth. Released earlier this week, the report highlights the synergy between well-planned growth and watershed protection:

"Poorly planned development can put terrible pressure on our communities' infrastructure and natural resources. If we fail to enact common-sense solutions to manage our region's growth, unsustainable sprawl will lead to shrinking forests, weakened natural flood protections, and greater pollution levels in our local streams and rivers - not to mention increased traffic, larger school classroom sizes, and higher cost of living . . .

"[But] supporting our region's growth and restoring the Potomac to full health are not mutually exclusive goals.

"Smart planning strategies foster growth and ensure the responsible protection of forests, farmland, and waterways. Communities can avoid sprawl by planning clustered areas for mixed residential and commercial use, and protecting forested lands. Cost-effective tree plantings and rain garden installations improve local water quality and beautify our communities at the same time. With foresight, we can meet growth demands and leave a legacy of clean water for future generations."

With excellent illustrations and clear writing, the report elaborates upon these strategies in rural, urban, and suburban areas of the massive watershed that drains into the Potomac's 380 meandering miles through Virginia, Maryland, and Washington, DC. The river provides drinking water to more than 4.5 million people, according to the Conservancy. Although the report focuses on one particular river, its lessons are instructive for watersheds across the country that are experiencing population growth along with aging urban infrastructure no longer capable of adequately conveying stormwater in a way that avoids polluted runoff.

Just before I read the new report on the Potomac watershed, I ran across a couple of articles highlighting an especially creative way of bringing more green infrastructure into older cities: greening urban alleys. For example, Jared Green of the American Society of Landscape Architects highlights how residents of the historic Fan district in Richmond, Virginia are turning the neighborhood's alleys into "arcadia" of green planting. Green emphasizes the opportunity presented by alleys:

"Given paved, impermeable surfaces like streets and parking lots can easily cover 30-40 percent of cities, urban policymakers and designers are increasingly redesigning the alley, in large part because of stormwater management issues. Chicago, Philadelphia, and Boston are all experimenting with applying permeable pavement to their ubiquitous back roads. While this material provides great environmental benefits, it really just looks like pavement. The approach taken by the neighborhood groups in The Fan not only offers environmental benefits but also creates beautiful public spaces and helps build communities."

Washington, DC is joining that list of cities experimenting with green alleys. Writing for The Washington Post, Mark Jenkins reported earlier this year that the city has already completed a handful of green alleys and has undertaken two new pilot projects under its RiverSmart program. Three kinds of permeable surfaces - permeable concrete, permeable asphalt, and preconstructed pavers - are being installed, along with rainwater-retention areas, and the projects' success will be monitored.

In Next City, Rebecca Tuhus-Dubrow argued earlier this month that stormwater control is only one of a multitude of benefits that can come with green alleys. Tuhus-Dubrow's article focuses on South Los Angeles, where in recent decades alleys have been seen as "forbidding places," not assets. But that could be changing:

"The vision is to convert them into vibrant corridors crawling with greenery, and covered with environmentally friendly surfaces. They are intended to provide play space, biking and walking routes, and a variety of ecosystem services. After six years of research and community organizing, [Trust for Public Land staffer Tori] Kjer and her colleagues have won strong support from the community for their Avalon Green Alley Network Plan, and the renovation of two alleys is scheduled to begin early next year.

"If the project is scaled up, it could have a substantial impact on the urban fabric: Los Angeles has a total of almost 900 miles of alleys, roughly the length of the coast of California. Proponents believe that on a citywide scale, green alleys could act as significant rainwater sponges, mitigate the heat island effect, and reduce vehicle use, as well as bring social and health benefits to nearby residents."

The opportunities could be especially significant because many park-deprived neighborhoods in Los Angeles are "alley-rich," writes Tuhus-Dubrow. Green alleys could provide enhanced play spaces for kids. (That makes great sense to me; even without any greening, kids play in the alleys in my DC neighborhood all the time, as did I as a kid in North Carolina.)

Green infrastructure offers many more strategies than just green alleys, of course. These just happen to be the stories that I ran across in the last couple of weeks. The essential logic of protecting a watershed facing population growth is really pretty straightforward: Maintain the rural landscape outside of cities and towns (with less polluting farming practices, please) while we practice smart growth and bring more natural processes into our developed areas.

The result can be great for the environment, for the economy, and for people if we do it right. My friend Kai Hagen, founder of Envision Frederick County (MD), eloquently sums it up in this short video produced in conjunction with the Potomac Conservancy report:

Move your cursor over the images for credit information.

Kaid Benfield writes about community, development, and the environment on Huffington Post and in other national media. Kaid's latest book is People Habitat: 25 Ways to Think About Greener, Healthier Cities.

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