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The Urban Underground
Fields, Forests, Brooks, and Blacktop - Can't We All Just Get Along?
By Ethan Nedeau
I was walking in downtown Amherst one lazy morning when I passed the sign for Tan Brook; on it was the silhouette of a wood duck. But there was no bridge or culvert, no sound of rushing water, and certainly no wood ducks. There was only a print shop, Italian restaurant, parking lot, and busy road. Curious and with time to kill, I wandered across the parking lot, between some buildings, and came to another road with the same sign-but still no wood ducks. Finally I knelt down and peered through stout iron grates at the corner of a parking lot and saw inky water several feet below. Tan Brook.
I spent the afternoon cutting through neighborhoods, hopping fences, and peering down storm drains to trace Tan Brook from its headwaters (a small pond near a cemetery) to its confluence with the Mill River (near a sports arena). From what I could see, about 80 percent of Tan Brook flowed through underground pipes that drained nearly 60 percent of the downtown area and nearby college campus. The brook flowed underneath vast parking lots, roadways, buildings, and athletic fields. Its waters were seasoned with a concoction of road salt, oil, grease, pizza crusts, dog poop, lawn chemicals, and other urban ingredients. I felt deceived. Living in a progressive and environmentally friendly community, I assumed our natural resources were revered. The Department of Public Works was kind enough to give the drainage system a name (albeit not the most flattering one) and a wood duck silhouette on the sign (a cruel sense of irony). Yet it was unfortunate that a stream that once drained a rich deciduous hillside and supported a diverse community of aquatic insects was now relegated to an underground drainage network, removed from sight and disconnected from our lives.
One of the greatest threats to natural ecosystems is mankind's tendency to wipe the natural slate clean when colonizing an area. In the United States, for example, we have cleared land, leveled hills and valleys, filled wetlands, channeled water into engineered conduits, and paved broad areas. This ensures that our structures have solid foundations that vehicles can travel smoothly and at a high speed, and that water and waste are quickly directed toward a convenient depository.
This high-intensity land use has steadily engulfed vast amounts of land throughout the United States. From 1982 to 1997, urbanized land increased by 25 million acres in the contiguous United States (NRI 2001), and the rate of development has continued to accelerate in the last decade. Experts predict that by 2025 there will be 68 million more developed (roughly the size of Wyoming) and that 25 percent of coastal areas will be developed (up from 14 percent in 1997) (Beach 2002, EPA 2001). Coastal watersheds are already greatly threatened, as coastal counties comprise only 17 percent of the land area of the contiguous United States but contain more than half of the human population (NOAA 1998, Beach 2002). Impervious surfaces—such as roadways, parking lots, and rooftops—now cover more surface area in the United States (nearly 45,000 square miles) than do all remaining herbaceous wetlands. An additional 1 million single-family homes, 10,000 miles of roadways, and countless other buildings and parking lots will likely be built annually in the coming decade (Elvidge et al. 2004).
In natural landscapes, the air, land, water, and living organisms comprise a dynamic ecosystem driven primarily by the hydrologic cycle. Impervious surfaces break the connectivity between the aboveground and below-ground portions of a watershed. This connectivity is of utmost importance to element and nutrient cycling and to virtually all ecosystem processes, including maintenance of biological diversity. It even affects climate. Therefore, it should not be surprising that impervious surfaces and engineered landscapes that intercept and direct water off the landscape cause myriad environmental problems. Impaired water quality, loss and degradation of terrestrial and wetland ecosystems, coastal pollution, water shortages, damaging floods, and harm to fish and wildlife populations can be partly or wholly attributed to impervious surfaces and poor water conservation.
Studies have demonstrated that when impervious surfaces cover greater than 10 percent of a watershed, freshwater and coastal ecosystems begin to suffer sharp and sometimes irreversible declines in health (Schueler and Holland 2000). Some Massachusetts watersheds have more than 50 percent of the land areas as impervious surfaces, especially in the Boston metropolitan area. Each day, millions of gallons of reusable freshwater are expeditiously removed from local hydrologic cycles rather than being recycled on the landscape. Rainwater and snowmelt are wasted because they run off rooftops, cannot infiltrate pavement, and flow quickly across monocultures of manicured grass. A one-acre parking lot produces 16 times more runoff than a one-acre meadow (Schueler and Holland 2000).
Worse, this wasted runoff leads to concentrated pollutants in water bodies. Surface water is directed toward gutters, which lead to storm drains, which empty into streams, rivers, or the ocean. Urban runoff is responsible for 55 percent of environmentally impaired ocean shorelines, 46 percent of impaired estuary miles, and 21 percent of impaired lake-miles in the United States (EPA 1998).
Soils that were once alive with roots, microbes, invertebrates, and burrowing vertebrates remain comparatively dormant beneath pavement and buildings in urban areas. Some creatures still lurk below the asphalt or live in storm drains, clinging to the sad remnants of once productive habitats. Ants spill out of fissures in the pavement to drag pizza crusts and scones into their underground labyrinths. Worms are displaced by street flooding and writhe on wet pavement until the clouds break and the sun turns the plump pink bodies into flat scorched ribbons. Larval sewer flies and rat-tailed maggots live in the anoxic urban stormwater soup and siphon oxygen from the atmosphere until they finally metamorphose into aerial adults and fly skyward through manhole covers. This is life in the urban underground: cosmopolitan creatures that can withstand almost every threat that humans throw at them.
Every so often, I find myself daydreaming about how my life could be different if I could start again, armed with a lifetime's worth of insight and clarity. I do not begrudge the learning process, but it is sad to think that I may get to apply lessons learned along the way only late in life. We build our communities just so—the ways that we develop and use natural resources evolve tremendously as we learn from centuries of experience. There is a growing awareness of the consequences of land use, urban design, and consumption on our lives and the environment. Urban design and planning is a rapidly evolving field of engineering and applied science, but putting theory into practice is challenging because cities are already built-existing infrastructure and design constrains new creativity. How can we start over?
One major challenge will be to reduce the effects of impervious surfaces and find ways to deal with urban runoff and non-point source pollution. Although the concept of reducing impervious surfaces is alluring to environmentally conscientious people who like to feel grass below their feet and relish the rich smell of earth, there are many practical limitations. Basketballs do not bounce on wood chips. Roller blades come to a rapid halt when people veer into the grass. And most people would not think of taking their sport utility vehicles off road. So how can we increase the porosity of the landscape to retain water and maintain existing infrastructure and preserve our quality of life?
Creative minds continue to explore ways to conserve water and restore ecosystems in an asphalt world, but the complexity can be overwhelming. Ideas range from rooftop gardens and cisterns that trap rainwater, parking lot designs, to regional planning and zoning (including bylaws and ordinances). At a regional scale, planning and zoning dictate where development will occur. At a neighborhood scale, planners focus on the arrangement of different land uses, street layouts, and optimum population densities. At a site scale, the focus on is on construction practices, stormwater designs, buffer widths, and landscaping. It may be impractical to redesign cities altogether—Boston's Big Dig is a testament to the costs involved with urban reconstruction (as of November 2005, nearly $15 billion had been spent on this effort). But as human populations soar in Massachusetts municipalities and urban sprawl engulfs rural areas, there is ample opportunity to design efficient environmentally friendly communities that conserve water.
New philosophies named "Smart Growth," "Smart Conservation," and "New Urbanism" guide development in some areas of the country. Smart Growth promotes compact development, reduced impervious surfaces and improved water retention, protection of environmentally sensitive areas, mixing of land uses (e.g., residential, office, and retail), public transportation, support for pedestrians and bicyclists, and other urban design features such as greenways. [Massachusetts Executive Office of Environmental Affairs has produced the Smart Growth Toolkit, a great resource for integrating these principles into local and regional planning; see www.mass.gov/envir/smart_growth_toolkit/index.html.]
Thinking of all the ways to reduce impervious surfaces and conserve water is like standing in a penny candy store with a nickel in your pocket—mouth watering, wistful, and wide-eyed—considering all of the glorious possibilities. If you are like my wife around candy, then you understand that the sadness of not having everything is often stronger than the happiness of having a nickel's worth. The decision is invariably slow and reluctant. But the need for water conservation is immediate; many of our streams and coastal waters are approaching an environmental tipping point beyond which they will be as woeful as Tan Brook.
Reviving the urban underground will require water: water to soak thirsty soils, water to recharge critical aquifers, and water to sustain streams and wetlands. This calls for a broad, long-term effort by all levels of government, land developers, building material suppliers, private businesses, and not-for-profit environmental groups. Finally, these efforts must be buttressed by a culture of conservation among citizens.
If you do not have the time or wherewithal to join local government or planning boards to effect change at a broad scale, just look around your home and yard for places to begin. I built a small pond in my backyard this summer, intercepting surface runoff before it got to the stormwater drain of the housing development next door. A green frog moved in within days—I have no idea where it came from but my satisfaction was immense. I am digging out the old cement walkways leading to my doorways in favor of wood chips, adding more gardens, and directing rooftop runoff into rain barrels. That is my contribution for now—rainwater will not reach Tan Brook and be whisked away to Long Island Sound. It will remain close to where it landed and support all the frogs, birds, and thirsty roots on my humble parcel of land.
Ethan is a science communicator, environmental consultant, and graphic artist. He lives amongst pervious and impervious surfaces in Amherst, Massachusetts. Ethan can be contacted through his web site, www.biodrawversity.com.
Beach, D. 2002. Coastal sprawl: the effects of urban design on aquatic ecosystems in the United States. Pew Oceans Commission, Arlington, Virginia. Available online at: http://www.pewtrusts.org/our_work_report_detail.aspx?id=30037 (Accessed Oct 20 2005).
Elvidge, C.D, C. Milesi, J.B. Dietz, B.T. Tuttle, P.C. Sutton, R. Nemani, and J.E. Vogelmann. 2004. U.S. constructed area approaches the size of Ohio. Eos 85(24):233-240 (15 Jun 2004). Available online at: http://ecocast.arc.nasa.gov/pubs/pdfs/2004/Elvidge_EOS.pdf (Accessed Oct 20 2005).
National Oceanic and Atmospheric Administration (NOAA). 1998 (online). Population, distribution, density and growth, by Thomas J. Culliton, NOAA's State of the Coast Report. NOAA, Silver Spring, Maryland. Available online at: http://oceanservice. noaa.gov/websites/ retiredsites/sotc_pdf/POP.PDF (Accessed Oct 20 2005).
NRI. 2001. Natural Resources Inventory. Natural Resources Conservation Service: United States Department of Agriculture, Washington, D.C.
Schueler, T., and H.K. Holland. 2000. The Practice of Watershed Protection. Center for Watershed Protection, Ellicott City, Maryland.
U.S. Environmental Protection Agency (EPA). 2001. Our built and natural environments: a technical review of the interactions between land use, transportation, and environmental quality. EPA 231-R-01-002. Development, Community, and Environment Division. Washington, D.C. Available online at: http:// www.epa.gov/smartgrowth/ pdf/built_exec_ summary.pdf (Accessed Oct 20 2005).
U.S. Environmental Protection Agency, Office of Water. National Water Quality Inventory: 1996 Report to Congress. Washington, DC: 1998.