Catalyst Summer 2017

Sounding the Alarm on Sea Level Rise

New UCS analysis finds many coastal communities face chronic flooding—and soon. The time to prepare is now.
Flooded downtown Anapolis, Maryland

Chronic flooding is already taking its toll in downtown Annapolis, Maryland. The city is facing the need for major investment to keep businesses in its vibrant waterfront district alive as flooding increases.
Photo: Matt Rath/Chesapeake Bay Program

By Pamela Worth

When Americans think about rising seas caused by global warming, we tend to summon mental images of neighborhoods underwater, as in New Orleans after the levees failed during Hurricane Katrina, or in New York after Hurricane Sandy. But as the new Union of Concerned Scientists analysis When Rising Seas Hit Home demonstrates, the effects of sea level rise can be slower and more insidious.

Some of us living in coastal communities have already experienced how the slow creep of sea level rise increasingly intrudes on our daily lives. In the decades ahead, millions more will feel it personally, or watch it unfold. A team at UCS set out to identify the amount of time coastal Americans have left to respond to sea level rise induced–flooding before it reaches an unmanageable point. The goal: to provide easy-to-understand, location-specific data on flooding, so that coastal residents can adequately prepare—and demand federal, state, and local leadership on this issue. It can’t come a moment too soon.

“From greater Boston to Key West, from the Everglades to Corpus Christi,” UCS Senior Analyst and lead report author Erika Spanger-Siegfried says, “hundreds of communities will be threatened with retreat from flooded areas—just in the next few decades.”

To analyze what’s in store for many communities in the coastal United States, the team set out to quantify the threshold of sea level rise–induced chronic flooding that would disrupt people’s daily lives and routines. After speaking with experts and residents of flooded communities, the team set the threshold at flooding that affects 10 percent or more of a town or city’s usable land, and occurs 26 or more times each year. From there, using storm gauge data and sea level rise projections under three different scenarios, the team crunched the numbers to determine which communities would be affected, and when.

The results are dramatic and surprised even many of our scientists and analysts—starting with the fact that 90 communities have already crossed the threshold of disruptive inundation.

Canaries in the Coal Mine

Many of these now-inundated communities are rural, with small populations, and are located where you might expect flooding due to the unfortunate combination of sinking land and rising seas: the Eastern Shore of Maryland and coastal Louisiana.

On Maryland’s Smith Island, where about 15 percent of the land is chronically inundated as of today, the population has declined by one-third over the last seven years; its primary school now has nine students total. On Isle de Jean Charles in the Louisiana bayou, the Biloxi-Chitimacha-Choctaw band has asked for and received federal assistance to relocate to higher ground as a community, as their land is lost to the sea. Such retreat may be in the future for hundreds of coastal US communities; others teeter on the threshold but are already experiencing the serious consequences of encroaching flooding.

Take, for example, the case of Fouché Sheppard, a well-known resident of Charleston, South Carolina. Sheppard is a poet and storyteller, and a longtime advocate for youth and seniors. She also worked as an administrative assistant at a medical office until she was fired for not showing up to work. The reason she couldn’t come to work: water. Sheppard says the streets that led downtown were blocked by what people in Charleston call “nuisance flooding”—a taste of the chronic inundation to come.

“I said to my supervisor, ‘You’re firing me because you’re lucky enough to live in one part of town and I live in another?’” recounts Sheppard. “I’m worried that if this keeps up, it’s going to affect a lot of people just trying to get by. How many people are going to lose their jobs when they can’t get to work because their car has been destroyed by flooding?”

Disparate Consequences

According to our analysis, by the year 2035—just 18 years away—the number of chronically inundated American cities and towns will jump to 170 given moderate rates of sea level rise, and 180 given a faster rate. One-third of these communities would lose the use of half or more of their land. In 20 communities, mostly in Louisiana, residents will lose more than 75 percent of their currently usable land, rendering much of today’s bayou communities unrecognizable. Other regions that will become chronically inundated are the Jersey Shore, North Carolina’s Pamlico Sound, and South Carolina’s Lowcountry.

Using a common metric known as the Social Vulnerability Index, UCS also found that more than half of the communities facing disruptive flooding by 2035 are home to low-income neighborhoods, and neighborhoods composed predominantly of residents of color. If poorer communities are located alongside wealthier communities and both are poised for chronic inundation, the former will of course have fewer resources with which to respond. But report coauthor and Senior Climate Scientist Astrid Caldas points out that rising seas aren’t the only problem facing low-income residents of coastal communities.

“If a wealthy coastal community faces inundation, and a less wealthy community is located on higher ground nearby,” she says, “residents could be priced out of their homes as those with more resources seek to move out of harm’s reach. It’s gentrification by rising seas.”

Disturbing Longer-Term Trends

Flooded community

In many rural communities, like Isle de Jean Charles in Louisiana (pictured here), flooding not only damages homes but also makes roads unpassable, keeping residents from getting to their jobs.
Photo: from “Can’t Stop The Water” by Cottage Films

Analyzing flooding in the latter half of this century, from 2060 to 2100, UCS identified three disturbing trends. First: by mid-century, large chronically flooded zones will emerge in cities and towns that seldom or never flood today, including several West Coast cities such as Alameda and San Mateo, California.  

Second: flooding projections for cities and towns begin diverging starkly depending on a moderate or high rate of sea level rise. Under a moderate rate, nearly 500 communities will be chronically inundated by 2100. That number increases to 670 under a higher rate.

“If we cut carbon emissions extensively, and sea levels then rise less quickly, we could save ourselves a lot of pain,” Caldas says. “But left unchecked, sea level rise will affect a much greater number of coastal communities, and a greater land area within them.”

Third: chronic flooding begins to profoundly affect dozens of major metropolitan areas. Among many other cities, large portions of Boston, Fort Lauderdale, New Haven, Newark, Oakland, and four of New York City’s five boroughs will be subject to chronic inundation in the moderate and worst-case scenarios.

“I admit I was stunned by these results,” says Spanger-Siegfried. “The economic, cultural, and social consequences of losing 10 percent of Manhattan’s land alone would be felt worldwide.”

Moving perhaps hundreds of thousands of Americans away from regular disruptive flooding, constructing defensive measures against such flooding, or some combination of both, would cost billions of dollars, she says. It would exact a more personal toll as well, as the emotional strain of abandoning a cherished home to rising water is multiplied thousands of times over.

“We need to recognize that we could be headed for an unprecedented federal crisis, with so many communities needing assistance at the same time,” says Spanger-Siegfried. “And that’s just focusing on the economic side. Culturally, historically—so much is under threat.”

Prevention, Adaptation, Retreat

The UCS analysis aims to offer communities an accurate assessment of what to expect in the years ahead. It also lays out a best-case scenario for preventing the gravest of these consequences. Our scientists and analysts found that extensive reductions in global warming emissions, coupled with a slower pace of ice melt, could spare hundreds of American coastal cities and towns from disruptive flooding. The report also provides recommendations for coastal communities and their residents, and governments at all levels, to respond to the slow infiltration of the seas effectively and equitably.

As affected communities approach the threshold of chronic inundation, they’ll confront difficult questions: should they stay in their homes and try to cope? Should they invest in measures like pumps, or raising homes and businesses to keep the water out? Or should they leave altogether? These questions reach beyond simple logistics to Americans’ identities, their cultures, their lives and livelihoods. And many who lack the resources to move, or to modify their homes to adapt to flooding, will not have the luxury of even these difficult choices.

An example of managed retreat, says Spanger-Siegfried, is when the state of New York following Hurricane Sandy offered favorable buyout terms to some 300 homeowners in Staten Island whose homes were at risk of further flooding. The terms were accepted, and several oceanfront neighborhoods are now empty, their ex-residents living on higher, safer ground elsewhere.

Spanger-Siegfried also points to commonsense policies such as restricting development in areas that are expected to face chronic flooding. “There’s no magic bullet that will work for every community,” she says. “But communities can use this information to put policies in place that can help more people cope.”

Any policy measures taken—for defense, adaptation, or retreat—must explicitly help the communities with the fewest resources to act, Caldas says. “People of color and lower-income folks can get left behind during storm recovery,” she says. “Relief money often goes to the communities that need it the least. It’s a disturbing pattern.”

Advice for Coastal Dwellers

To learn when your community might reach the threshold of chronic inundation, you can visit the interactive map UCS created to accompany When Rising Seas Hit Home. The full report, which includes recommendations for smart, effective policies to respond to sea level rise–induced flooding, is available for download; you can also read about Americans who are already experiencing disruptive flooding, and what they’re doing about it.

If your community is at risk, UCS urges you to contact your local, state, and federal elected officials and make a case for investing in science-based adaptation measures, and for federal action on global warming emissions. You can also ask what your city or town’s long-term and short-term plans are for managing rising seas and disruptive flooding. If your community is on the UCS flooding map and has no plan in place, ask to meet with your elected officials and local planning committee.

“The science is clear: Americans can count on the fact that sea level rise will reshape many of our coastal communities,” says Spanger-Siegfried. “Most of us who’ll be affected still have time. We must use it to plan wisely.”



Nicole Hernandez Hammer: Helping Neighborhoods Prepare for Sea Level Rise

Nicole Hernandez Hammer

Photo: Audrey Eyring/UCS

In South Florida, Miami Beach garners the most headlines, and expensive solutions related to sea level rise–induced flooding; hundreds of millions of dollars have already been invested in pumps and other mitigating measures. Over the bridge in the city of Miami, however, entire neighborhoods are at the mercy of rising seas with little planning or money invested to help them—and many residents aren’t aware that the sunny-day flooding ruining their cars and closing their roads is caused by sea level rise. UCS Climate Science and Community Advocate Nicole Hernandez Hammer has worked the last several years to change this.

Hammer has spent much of her professional life studying the effects of sea level rise and climate change on her beloved city. In the last decade, she’s created maps of Miami’s lowest-lying neighborhoods, where high tides are likely to cause flooding, and then visited those at-risk neighborhoods to confirm the inundation.

In the predominantly Hispanic neighborhood of Shorecrest, on Miami’s upper east side, Hammer brought together community leaders and nonprofit partners at events where she explained the science behind Shorecrest’s flooding, and how it was likely to get worse. It took more than a year to draft, but the Shorecrest sustainability manager recently sent Hammer the neighborhood’s preliminary plans to address chronic inundation. Hammer’s science education and advocacy, combined with a community’s initiative for preservation, may well have saved one neighborhood from being caught unaware by worsening floods.