Rising sea levels pose a serious threat to cites like Boston, New York and Miami Beach. So what are they doing to protect themselves?

The US cities at risk of flooding - and how they deal with it

Tropical storm Harvey may have bared its teeth at Houston, but other cities in the US have felt the pangs of nervousness. Several cities are vulnerable to the fiercer storms and sea level rise that are being fueled by climate change.

Cities, by their very nature, struggle during flood situations. Water that would have been soaked up by grass and other vegetation washes off the concrete and asphalt of urban areas and, if not properly diverted away, can inundate homes.

Add in, as in Houston’s case, lax rules around property zoning and a federal flood insurance system that repeatedly pays out for damage to poorly situated houses, and it’s clear cities have much work to do to cope with the changes upon them.

Harvey brought a huge amount of rainfall, but cities now face flooding threats even without a major storm. “Rare events are going to become more common in the future strictly due to sea level rise,” said William Sweet, an oceanographer at the National Oceanic and Atmospheric Administration (Noaa).

“We are already seeing flooding in property and the streets in Charleston, Norfolk and Miami on sunny days, driven by the tides. That is a looming crisis that is only going to grow more severe over time.”

The nightmare of a Harvey (or Katrina or Sandy) has led to many cities opt for huge sea walls and other expensive engineering fixes. But there is no easy solution – a sea wall simply pushes the water elsewhere, perhaps on to a neighbor’s head. The water has to go somewhere and decades of development on flood-prone land has left little space to maneuver for some municipalities.

“There are coastal cities at risk from an extreme event and they have giant sea walls or houses on stilts,” said Sweet. “But then there are communities that don’t face a big hurricane threat but water is bubbling up from underneath them. They can’t defend against this sort of flooding. You can’t build a wall everywhere.”

Some progressive cities have started to look at alternative approaches, most notably from the Netherlands, where communities “live” with the water, allowing certain areas to flood while aggressively defending critical infrastructure. Natural sponges such as parklands, wetlands and dunes are now also in vogue with city planners.

But as attitudes to flooding slowly shift, the problem is escalating. Scientists are now confident that hurricanes will become more powerful, fed by a warming, moisture-laden atmosphere, while more common “nuisance” flooding will become so frequent along parts of the US east coast that they will occur once every three days by 2045. By around this time, a majority of US coastal areas are likely to be threatened by 30 or more days of flooding each year.

So which cities are at risk and what are they doing about the threat?

Boston

Bostonians experienced a bumpy past two years after record snowstorms in 2015 were followed up by the driest summer in the city’s history. But it’s the risk of flooding that is the paramount environmental concern for city officials.

Marty Walsh, Boston’s mayor, warned a major storm could “wipe out” the heart of the city following the unveiling of a report last year that stated billions of dollars’ worth of real estate was at risk from rising seas and the threat of a Hurricane Sandy-like event. At 5ft of sea level rise, which is feasible within the coming century, Logan airport starts to disappear and water will lap at the edges of Harvard’s campus.

Several remedies are being considered, most ambitiously a huge sea barrier that would form a protective arc around Boston Harbor.

Facebook Twitter Pinterest Photograph: Daniel Kaesler / Alamy Stock Pho/Alamy Stock Photo

New York City

Hurricane Sandy, which poured water into New York City’s subway system and cut power to its inundated financial district, was a stark reminder that even the richest cities in the world cannot escape the ravages of climate change.

The seas that wrap around the city are expected to rise by as much as 75in by the end of the century, a scenario that would imperil both of its airports, JFK and LaGuardia, and slice away sections of Brooklyn and lower Manhattan, much of which is built on artificially filled-in land.

With some of the world’s most valuable real estate to protect, the city threw its weight behind plans for a 10 mile-long barrier, consisting of earth berms, walls and gates, ringing lower Manhattan. The project, known as the “Big U”, is still several years and hundreds of millions of dollars away.

Facebook Twitter Pinterest Photograph: Mary Godleski/ASSOCIATED PRESS

Atlantic City

Perched on a low-lying barrier island which is being chiseled away by the ocean, Atlantic City is particularly vulnerable to flooding. The city, devastated by Hurricane Sandy in 2012, has faced a painful period of rebuilding that may one day become untenable – research has suggested that rapid sea level rise will see a Sandy-like event sweep over the area every five years or so by 2100.

But even without a major storm, Atlantic City is troubled by seas that are rising at around 1.5in a decade. High tides regularly cause the back bay area, where most of the low-income housing far from the tourist strip is found, to flood. There is no clear plan as yet to deal with this threat.

Charleston, South Carolina

Charleston experienced 50 days of flooding in 2016, according to Noaa, simply through high tides. In the 1960s, there were around four days a year of flooding.

The problem is set to escalate further, with the Union of Concerned Scientists predicting that by 2060, under moderate sea level rise scenarios, nearly a fifth of low-lying Charleston will be flooded every other week, on average.

In July, the city announced a $100m plan to raise the low battery, an historic sea wall that protects much of Charleston’s heritage, by two and a half feet. The project will take more than a decade to replace the deteriorating sea wall.

“This is a front-burner project for us, let’s put it that way,” said Jacob Lindsey, the city’s planning director.





Tampa

Considered by the World Bank one of the most at-risk areas in the world for sea level rise, the Tampa Bay region has been quietly bracing itself for the worst for several years.

The area’s pristine beaches have avoided a direct hit from a major hurricane in nearly a century but a report released in July warned that a category three event, or stronger, could result in $175bn in damages to Tampa Bay. Much of this is to do with geography – the sloping, shallow shelf of the bay would create a funnel where water would surge into properties should a hurricane hit.

Tampa has attempted to bolster flood protections for critical buildings such as hospitals but there is very little the city could do if an enormous hurricane formed in the Gulf of Mexico and bore down on it – planners have looked at the worst case scenario and predicted a grim death toll of around 2,000 people.

Facebook Twitter Pinterest Photograph: Alamy Stock Photo

Miami Beach

“We are facing an existential threat here,” admits Kristen Rosen Gonzalez, Miami Beach’s city commissioner. Pancake flat and built on porous ground that is slowly sinking back to the seabed, Miami Beach is surrounded by seas rising three times the pace of the global average.

The entire southern section of Florida is at risk from climate change but Miami Beach is eyed with particular concern by other cities. After all, if this wealthy area can’t engineer its way out of trouble, where can?

Miami Beach has spent around $200m raising the height of streets in vulnerable areas and has a network of pumps to force water back off the streets after ‘sunny day’ flooding. Even more radical fixes will be required – if sea level rise isn’t quickly tamed then this vacation hotspot will be virtually swallowed up by the end of this century.

Facebook Twitter Pinterest Photograph: James Nielsen/AFP/Getty Images

New Orleans

New Orleans still bears the scars of Hurricane Katrina, which resulted in much of the city becoming inundated with water in 2005. More than 70% of New Orleans’ occupied housing was damaged, with 1,500 deaths in the city and its surrounds.

The failure of New Orleans’ levees prompted the building of the largest storm surge barrier in the country, labelled the “Great Wall of New Orleans”. But the city has also turned to developing more natural remedies, such as parkland that would soak up water, along with seawalls.

“We’ve invested a great deal but now we’re moving into more green infrastructure because we’ve decided we just can’t build enough pipes to pipe our way out of what we’re seeing as these projections,” said Jeff Hebert, New Orleans’ chief resilience officer.