Coastal cities need to rethink how they deal with rising waters
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An environmental engineer by trade, Paul Olsen has spent the last few decades helping people understand how rising seas threaten the places we live.
"I still use Tangier as my closer," Olsen says of one of Virginia's most notable sinking islands. It is in the Chesapeake Bay, which is home to a historic community of oystermen. Tangier helps illustrate his point: rising waters aren't just a fear for the future. "It scares the heck out of people."
If that doesn't do the trick, Olsen invokes the memory of Holland Island. It was home to a thriving fishing community for a century. That was until its last house succumbed to the bay in 2010.
"They failed to adapt, retreat or defend," says Olsen. After almost 30 years with the U.S. Army Corps of Engineers, he is helping Virginia navigate rising seas as a program director at the state's Old Dominion University.
In San Francisco's Bay Area, landscape architect Kristina Hill agrees on the options water-threatened communities must consider. But she might disagree on which ones are worth shoring up.
"I actually think what's going to happen is we're going to withdraw from a lot of places where there are small towns and vacation homes, because they won't have the capital to do big projects," says Hill. She is an associate professor at the University of California-Berkeley. The towns that need saving on Chesapeake Bay islands are smaller villages with populations of less than 300. According to Hill, moving earth to protect those towns isn't the best use of public funds.
But for population centers like San Francisco, New York City, New Orleans and Norfolk, Virginia, she adds, architects are looking to adapt their structures, "to keep developing in a way that is ready for sea-level rise."
Somewhere between retreating and building a giant wall to keep the waters at bay is a middle ground that acknowledges inevitably higher waters or periodically devastating storms. And it builds with them in mind. In American cities dealing with rising seas, sinking landscapes and increasingly intense squalls, "transitional architecture" is one way to inhabit the treasured coastlines as long as possible.
The approach is already being implemented in parts of Europe.
In the Netherlands' port city of Rotterdam, architects have begun building ultramodern homes on pilings in ponds. The new homes are accessible by earthen berms. They create a honeycomb-like pattern of water-absorbing ponds.
HafenCity, in Hamburg, Germany, is recruiting residents to modern apartment buildings. Instead of shielding the buildings from storm surges, architects designed them with parking garages on the first floors. Elsewhere in the city, they placed costly assets like metro stops on higher levels. Parks feature few trees. Sturdy playgrounds are built to withstand gushes of water during heavy rains.
"They call this 'tiered development,' because it's set up in vertical layers," Hill explains. "There's a layer that can be flooded, (and) one that's protected and only in a huge emergency would be flooded. And then a layer that would never be flooded."
Though such water-minded cities look futuristic, the concept of structures built to withstand intermittent flooding isn't new. David Waggonner, president of New Orleans-based Waggonner & Ball Architects, says that's how residents of the Bayou used to build their homes, too.
"Maybe it rained hard. But if it was masonry at the bottom and your principal living areas were above that, you could live on," Waggonner says. "You can learn a lot from the past, the way people built."
In response to the devastation of Hurricane Katrina in 2005, New Orleans and the federal government built an even bigger floodwall to defend the city. Waggonner says residents still would be wise to have a backup solution for the water.
"You need to know where you're building, what the landscape is and has been," says Waggonner. Otherwise, "you're working against it."
Hill sees solutions like New Orleans' floodwall as "a dumbing down of the human ability to track and respond." She prefers solutions that encourage cities to work within their natural settings. Like those implemented in HafenCity and Rotterdam.
Hill says many American cities will require a mix of defensive and adaptive structures to endure higher waters. One natural line of defense in a city's arsenal is its wetlands.
In San Francisco's Bay Area, wetlands are a subject of debate. Some argue that the development and highways that have filled them in over the years should be removed. They believe it would return marshes to their natural state.
Wetland restoration projects in northern parts of the Bay Area already have returned thousands of acres of former industrial salt ponds to marsh habitat. But imagine San Francisco's iconic coastline highway giving way to lush bay grasses and fishing egrets, along with the city zoo and multi-million-dollar Sunset District homes.
Even after a city concedes that it already built where protective wetlands once were, "it's difficult to pull up stakes and allow a wetland to take over," says Hill.
It's especially difficult to pull up stakes when they involve national assets like shipping ports and the world's largest naval base. Such is the case in Norfolk. The Hampton Roads region where Olsen and these landmarks are based has seen water levels rise 14 inches since 1930.
Olsen is preparing for a future in which some of the naval base's piers will be abandoned. They may be rebuilt elsewhere. And the Navy will have to double down on protecting the rest. The roads that carry military personnel to their vessels will need to be raised above flood levels. Some homes will need to be built on pilings or with flood vents to minimize damage to their foundations.
If those waters continue to rise at a rate of six millimeters per year, the base and surrounding area will need to prepare for another foot of water in the next century.