Building Green Cities
Using the power of nature to make cities more resilient and livable places.
Cities are growing—fast. By 2050, two-thirds of the world’s population will live in urban areas. An increasing urban population means that cities are expanding their footprint at an alarming rate. It also means fewer people have access to nature’s benefits.
Even in cities, we depend on natural habitat for food, clean water, clean air and mental health. The Nature Conservancy’s urban conservation focus in the capital region is on stormwater runoff, the fastest growing source of pollution to our rivers and to the Chesapeake Bay.
Growing Problem, Natural Solutions
Stormwater pollution is caused when rainwater falls on impervious surfaces—including sidewalks, parking lots and roads—where it mixes with oil, sediment, trash and other pollutants. It then flows into our cities’ sewer systems and rivers.
Replacing, buffering or retrofitting impervious surfaces with water retaining green infrastructure like “rain gardens” allows polluted stormwater to be captured and cleaned. Water is absorbed and filtered by the plants, topsoil, sand and gravel layered within a rain garden.
One of the oldest methods for capturing runoff, the stormwater pond, is getting a digital makeover. No longer simply collecting rainfall washing off pavement and lawns, "smart" ponds anticipate precipitation before it begins and adjusts to reduce downstream pollution and flooding.
Old Problem, New Solution
In a program that could serve as a national model of environmental stewardship, TNC is partnering with the Maryland Department of Transportation (MDOT), the Maryland Department of the Environment (MDE) and technology firm Opti to implement advanced stormwater control technology at existing sites to help curb local flooding and reduce stormwater runoff to the bay.
Smart pond technology uses sensors and software to monitor real-time conditions such as water level and storage volume. The system uses internet-based forecasts to remotely operate valves that control timing and volume of water discharge. Longer retention time increases water quality by capturing more sediment and nutrients. When rain is forecast, the system can automatically open valves to drain the pond prior to precipitation. This helps maximize storage efficiency and can reduce downstream flooding.
Working together to harness technologies that deliver low-cost solutions to water pollution, our hope is that this innovative approach can be replicated across the bay watershed and beyond.
Investing in Partnership
In 2019, we made substantial progress with our D.C. stormwater program. We completed the construction of the second phase of stormwater retention infrastructure at Mount Olivet Cemetery—a project that now captures more than 3-5 million gallons of stormwater runoff each year.
Mount Olivet Cemetery was founded in 1858 in what was then a rural part of Washington, D.C., to carry out the Catholic Church’s ministry. Now that the cemetery is almost full, the church is exploring new ways to use the cemetery grounds to answer Pope Francis’ Encyclical on the Environment, Laudato Si', to respect and care for the earth.
This shared interest in the natural world has led to an innovative collaboration with the Archdiocese of Washington to use non-burial lands to address the growing environmental problem of urban stormwater pollution.
Designs for the green infrastructure project were aimed to maintain the sanctity of the grounds while also enhancing them. All work conducted in the surveying, planning and implementation of the modifications was done in close collaboration with the cemetery to ensure that the burial sites would not be disturbed, and construction would not disrupt scheduled burials or impede the ability of people coming to visit loved ones buried at the cemetery.
The project at Mount Olivet Cemetery also generates more than 160,000 stormwater retention credits annually, which are sold on D.C.’s stormwater credit-trading market, generating returns on investment that go right back into the ground in the form of new projects.
As we plan new stormwater projects in D.C., we are now equipped with a valuable resource, thanks to another project completed in 2019.
Working with Dewberry, an environmental consulting firm with engineering and geospatial analysis expertise, the firm analyzed the D.C. landscape to produce a series of maps that identify sites across the District where nature can help people by reducing stormwater pollution, flooding and urban heat. The maps will guide our future projects and those of our partners as we work together to create a healthy urban environment for both people and nature.
TNC's work at Mount Olivet cemetery started as a way to address stormwater runoff in the Anacostia river, but it has grown into so much more.
In June 2019, a new memorial green space was formally dedicated at Mount Olivet. The space will address multiple urban conservation needs while also providing visitors with a place to rest and connect with nature.
The project was constructed on a large open hill where many men, women and children—including those who were enslaved—were buried over the cemetery’s 160-year history, some without memorial markers. The space was designed with direct input from the community through a series of meetings facilitated by TNC where community members offered thoughts and feedback during the design process.
The more than 100 new trees planted at the site by partner organization Casey Trees and TNC will not only provide shade for visitors as they grow, but also provide habitat for native species, filter rainwater through their roots, and help to reduce the urban heat island effect that occurs in areas with little to no tree canopy.
This site is TNC's first collaboration with Nature Sacred—an organization focused on the creation of urban green spaces founded by the TKF Foundation. Both Nature Sacred and TNC have a vested interest in connecting people with nature and work under the shared belief that caring for nature is vital to human health and well-being.
In recognition of this, the community designed green space has been accepted as a prescription site for Park Rx America. Patients who are prescribed nature by their doctors can "fill" their prescription by spending time at the Mount Olivet set.
In addition to providing human benefits, supporting native species and capturing stormwater, the new garden spaces complement the extensive green infrastructure that TNC has already installed across Mount Olivet Cemetery to capture millions of gallons of stormwater runoff that would otherwise flow into the Anacostia River.
Make a Difference
Together we can find creative solutions to tackle our most complex conservation challenges and build a stronger future for people and nature. Will you help us continue this work?