By Anthony Flint

NEW ORLEANS – Even with aggressive action on climate change, scientists agree that a global temperature rise of some kind is inevitable, triggering sea level rise, more intense storms, and an array of other chain-reaction disruptions to life as we know it. And in the typically sinister way that the climate cataclysm plays out, these impacts will hit hardest in the places most people live.

More than half of the U.S. population lives in 673 coastal counties. In China, the world's most populous nation, 60 percent of the country's 1.2 billion people live in coastal provinces. Worldwide, rapid urbanization in coastal and delta mega-cities includes widespread informal settlement, a recipe for disaster for the most vulnerable populations.

The good news is that planners are paying attention. Cities, as places of density and transit, can make great strides in mitigation, the reduction of greenhouse gas emissions. But coastal cities must engage in adaptation on a parallel, and in many ways integrated, track. There is no more urgent role for planners in the years ahead, says Edward Blakely, the former recovery director for New Orleans, than to plan and help implement adaptation to climate change.

Coastal cities are already well aware of the breadth of the problem. Jakarta is confronting annual flooding that strains a colonial-era layout, and Dhaka in Bangladesh has struggled with stronger typhoons. At the Yantgze and Pearl river deltas in the Shanghai and Hong Kong regions respectively, chronic flooding, coastline erosion and wetlands deterioration, storm surges, and punishing storms are wreaking havoc on areas that have been attracting the most intense in-migration and urbanization. Sewer overflow and saltwater intrusion, with impacts on drinking water, public health, and agriculture, are key areas of concern, as well as the vulnerability infrastructure such as power plants, port and refining facilities that will be flooded and potentially permanently underwater in the decades ahead.

The city ravaged by Hurricane Katrina five years ago, of course, has had the most vivid glimpse of the future. The path forward for New Orleans ranges from evacuation planning and  relocation, “hard” solutions such as seawalls, weirs, tidal barrages, levees, and the redirection of waterways, as well as the restoration of natural systems to manage flooding. "The world is watching not only the city, but the planning field as well," said EPA Administrator Lisa Jackson, who grew up in New Orleans, speaking at the American Planning Association's National Conference in April.

The adaptation strategies detailed in the Delta Urbanism (  symposium at the conference reflected a comprehensive approach informed by the people who know water better than anyone – the Dutch. The most promising innovations coming out of the Dutch Dialogues, with support from Waggonner & Ball Architects, the APA, TU Delft, and the Netherlands Water Partnership, are based on the concept of giving water more space – “room for the river” – in terms of spatial planning.

The approach involves lowering dikes in targeted areas to better enable flood protection in other areas with high populations or valuable infrastructure, says Tulane University’s Douglas Meffert. While this practice sounds counterintuitive, allowing certain natural habitat or in some cases, farmland areas to flood during high river stages reduces the vulnerability of nearby urban centers, he says.

A critical component is the role that nature is allowed to play. The restoration of wetlands and natural systems in coastal and delta cities has moved to the forefront. A promising model is found in the Yangtze River estuary's wetlands and mudflats, which continue to grow due to the dynamics of riverways, tides, and sediment.

When Shanghai’s Pudong wetland was drained and developed in the  1990s to construct the Pudong International Airport, the Jiuduansha Shoals in the Yangtze Estuary were ecologically engineered to mitigate for this wetland loss and create a new habitat for the migratory shorebirds and waterfowl. The attraction of the new vegetated habitat had the added advantage of reducing bird strikes in jet engines, but the big benefit is typhoon hazard reduction for nearby developments and infrastructure. Other efforts in China were detailed by Lingqian Hu, senior regional planner at Southern California Association of Governments, who presented a Tsinghua University paper, “Climate Change and Urbanization in the Yangtze River Delta”; and He Canfei, professor at Peking University and associate director of the Lincoln Institute-Peking University Center for Urban Development and Land Policy ( in Beijing.

Future projects could not only use natural systems as flood control solutions but better use diversions for wetland restoration and creation projects, as well as improved water storage practices in population centers, such as catch basins, green roofs, gardens, recreation parks, waters squares and pervious surfaces.

“We’re capable of doing these things,” said Robert Yaro, president of the Regional Plan Association, and part of a team of researchers being led by Blakely, comparing adaptation scenarios in the U.S. and Australia, which share some similar characteristics. A century ago, Charles Eliot used a combination of hard infrastructure and natural systems to manage the Charles River in Boston, which was followed by the Charles River Dam project to further guide storm surges and flooding. “It may take a really bad event to make people pay attention.”

In the long haul, Yaro said, coastal cities will see dramatic changes – huge tidal barriers at the Golden Gate and ringing New York City, with the San Francisco Bay and Long Island Sound potentially turned into freshwater lakes. Large areas will be uninhabitable and water supplies will be a particular problem he said. “We basically can buy ourselves 300 years,” he said. “We’re at the place where Amsterdam was in 1890.” Taking adaptation seriously is a first step; paying for it will be the next. Blakely suggests that in the U.S., cities pay into a national adaptation fund, on an insurance model. Those metropolitan regions that take the best protective measures get a break on their premiums.

Building on these innovations will require smart people who not understand policy, urban planning and earth science, but the dynamics of deltas, sediment, and discharge. The challenge is so daunting, it’s hard to maintain hope, or to believe in much beyond the bright prospects of the seawall-building business. But adapting to climate change in coastal cities is shaping up to be the central project of planning for the rest of this century.     Anthony Flint is a Boston-based writer at the Lincoln Institute of Land Policy