Public-private partnerships can fund innovative, forward-looking solutions to help fight flooding in coastal cities.
Flooding is a critical problem for property owners and developers in coastal areas. The search for solutions has opened the door to innovative approaches involving architects, city planners and investors.
Advanced adaptive architecture and design principles are creating buildings that use — and even benefit from — water flow in coastal cities. These promising technologies have the potential to generate opportunities for public and private investment.
In China, An Innovative Use of Water Flow
The Chinese government is investing heavily in its Sponge City Initiative, a program launched in 2015 that uses urban infrastructure and design projects to reduce flooding from rainwater runoff, increase groundwater absorption and replenish the water supply. According to CNN, the country’s goal is to have 80 percent of its urban areas absorb and reuse at least 70 percent of rainwater by 2020.
Nanhui New City (Nanhui), renamed in 2012 from its former name of Lingang New City, is one of 30 Sponge Cities in China. Construction of Nanhui began in 2003. When completed in 2020, the city will have cost the Chinese government $4.5 billion to build.
This city is a planned “green” community roughly 40 miles from Shanghai, and about 45 percent of the city rests on land reclaimed from the sea. Meinhard von Gerkan, a renowned German architect known for his contemporary designs, masterminded an ingenious vision for the municipality. It’s bursting with state-of-the-art “green” designs for integrating controlled water infiltration into Nanhui’s urban landscape. He took inspiration for the city’s layout from the image of a single drop of water creating concentric rippling circles — the city is divided into five circular zones with a large artificial lake at its center. The lakefront area includes a district with commercial and leisure facilities.
Different design elements are incorporated into the city’s construction to maximize the urban landscape’s ability to coexist with the sea and reduce flooding. In contrast to other cities that are impervious urban concrete deserts, Nanhui abounds with major green spaces, including wetlands and bioswales.
Bioswales are the larger cousins of rain gardens. Generally, a bioswale is an area located next to an impervious surface, such as a roadway, parking lot or sidewalk, that is composed of landscaped native plants and grasses that can withstand heavy rainfall. The mulch, well-drained soil and small stones generally found in a bioswale filter water through the roots of the plants so that it gradually seeps into the soil and then finds its way into the water table below the soil.
In Nanhui, streets are made of permeable pavement — also known as pervious asphalt or porous concrete — that turns the soil underneath into an aquifer for absorbing and storing fresh water.
One of the major benefits of a pervious roadway is that it traps sediment while providing a home for naturally occurring micro-organisms that digest oils from vehicles as well as other pollutants. This allows the contaminants to biodegrade within the pavement, leaving carbon dioxide and water as the remaining byproducts. Similar to a bioswale, this water percolates through the small rocks under the pervious pavement to recharge the groundwater aquifer.
Permeable roadways also reduce installation costs, because there is no longer a need for underground piping, storm drains or grading. Nevertheless, frequent maintenance may be needed to “vacuum” or flush the roadway so that solids and particles do not get trapped and clog the pavement’s pores.
The widespread use of bioswales and permeable pavement, together with canals crisscrossing the city to accommodate incoming water, establish Nanhui as a water-resilient city of the future. Indeed, by pairing innovative, environmentally focused infrastructure and building designs, Nanhui has become a model city for the U.S. and elsewhere in terms of using science and engineering to inform water-friendly architecture and adaptive infrastructure design.
Nanhui hopes to become China’s largest Sponge City, and public-private partnerships with international and local entities have helped finance the city’s build-out.
According to Urban Transformations based at the University of Oxford in the U.K., the Shanghai Lingang Area Development Authority (SLADA) is responsible for developing Nanhui’s master plan, allocating its resources and managing its land. Similar to how a developer engages its subcontractors, SLADA engaged eight major development companies, each having the responsibility to develop a section of Nanhui.
Although all of these development companies belong to the state, they operate like private companies whose purpose is to generate profit. Because these firms are located in China, it is difficult to obtain specific information regarding costs related to roads, power, water, buildings and key sources of renewable energy. However, despite the absence of this information, it is clear that public-private partnerships can play a crucial role in financing and accelerating resilient developments.
While Nanhui shows the potential of communities planned from the ground up, the Chinese model of populating a Sponge City is not viable for existing coastal cities.
Sponge Cities begin as “ghost cities” that are devoid of population while being built. Once construction is completed, the picture changes completely. China intends to “seed populate” these municipalities by locating university campuses — eight in Nanhui’s case — as well as government headquarters, bank offices and state-owned companies in them.
By 2016, the universities in Nanhui had attracted approximately 100,000 students. Their presence has spurred economic growth, with various types of businesses opening to meet the burgeoning population’s needs. The plan is for Nanhui to eventually support approximately 800,000 residents, and it will be a model for other Chinese cities in need of state-of-the-art water infrastructure design.
While Nanhui is a city built from scratch in a relatively short amount of time, the architectural and design elements used there could be replicated in other countries and in large coastal cities such as Miami and New Orleans. Of course, it would be nearly impossible and quite unrealistic to evacuate those densely populated areas and transform them, but modifying their existing built environments to embrace Nanhui-style adaptive architecture could be done.
Many types of water- and eco-friendly architectural designs already exist. For example, fog catcher nets that collect fresh water from the air for irrigation and drinking are used in one of the driest place in the world, the Atacama Desert in northern Chile. Similar innovations could be a boon for coastal smart cities by making fresh water available from more sources.
Singapore’s Gardens by the Bay nature park showcases a futuristic architectural project known as the Supertree Grove. Employing the concept of biomimicry, which Wikipedia defines as “the imitation of the models, systems and elements of nature for the purpose of solving complex human problems,” each 25- to 50-meter-tall Supertree has photovoltaic cells that capture sunlight during the day so that lights attached to the tree’s branches can illuminate the garden at night. While they don’t have roots to trap rainwater, each Supertree is designed to channel water to irrigation systems as well as to fountains in the park. The Supertrees support more than 200 species and varieties of ferns, orchids, vines, bromeliads and tropical flowering climbers.
American architects have also conceptualized forward-looking inventions. One idea involves water-inflatable barriers that rise when higher tides endanger coastal cities. These can be deployed quickly, and they don’t require the labor needed to build a levee or fill sandbags. Another innovation is buildings with water systems that fill aquariums throughout multiple floors. The fish in the tanks can be used either as a food source or as décor, with the fish-fertilized water being pumped to the top of the building to nourish plants growing in a rooftop garden.
Putting Water to Work
A combination of innovative design and adaptive architecture, backed by public-private partnerships, can leverage, instead of combat, water-rich environments. Cultivating the ability to use excess water and finding creative ways for city residents to benefit from it will make coastal cities more resilient. Making the urban landscape more permeable alleviates flooding and also is a catalyst to shift mindsets so that residents of coastal cities take a more sustainable approach toward the built environment and their surroundings.