Climate

Major U.S. Cities Will See 10 Times More Coastal Flooding By 2045

CREDIT: AP Photo/J. Pat Carter

Flooding during high tide could occur so frequently in some U.S. cities in the future that parts could become “unusable,” according to a new report.

The report, published by the Union for Concerned Scientists, looked at 52 National Oceanic and Atmospheric Administration tide gauges in coastal cities in Florida, Maryland, Georgia, Virginia and other states. UCS analyzed the states’ flooding risk under mid-range sea level rise predictions taken from the White House’s National Climate Assessment — an estimate of 5 inches of sea level rise by 2030, and 11 inches by 2045. It found that tidal flooding could triple in some cities in 15 years and occur 10 times as often in most cities in the next 30 years.

The Mid-Atlantic states are particularly vulnerable, the report found. A tripling of tidal flooding events in these states would mean that, in some cities, flooding could occur multiple times per week. The report also found that by 2045, one-third of the cities and towns looked at could start experiencing tidal flooding more than 180 days each year, and nine cities would see flooding 240 times each year.

These floods aren’t the type that cause death or major destruction, the authors of the report noted on a press conference Wednesday. They’re “nusiance” floods, the kind that force residents to wade through water on their way to work and move their cars before the tide comes to avoid saltwater damage. But as sea levels rise, there’s likely only so much of this flooding that communities will be willing to take, report co-author Erika Spanger-Siegfried said. If the flooding becomes chronic, some areas may be forced to decide whether to relocate businesses and homes.

ucs tidal flooding

CREDIT: Union of Concerned Scientists

The report highlighted the challenges faced by some of these cities in adapting to sea level rise and the more frequent high-tide flooding that comes along with it. Tybee Island, Georgia, has already seen tidal floods double to 10 a year, up from five or fewer 40 years ago. The island’s Highway 80, which is the main highway leading onto the island and also serves as an evacuation route, and has become prone to tidal flooding.

Paul Wolff, Tybee Island’s longest-sitting member of the city council, said during the press conference Wednesday that sea level rise is a “slow-motion storm surge that doesn’t go away.” Wolff the city is tackling the threat of increased flooding from multiple angles, building oyster reefs to help protect the shorelines and adopting a 25-foot buffer around the island’s marshfront properties. Still, more needs to be done to protect homes — he said he tries to persuade residents to invest in raising their homes rather than take on more expensive flood insurance — and to protect Highway 80.

“For us, this isn’t theoretical science — it’s a real life situation,” Wolff said.

Miami, Florida has already grown accustomed to high-tide floods, events that, at least in some parts of the city, “never used to happen.” By 2030, the report states, those “sunny-day floods” will become nearly eight times as common as they are now, occurring on average about 45 times each year instead of the six residents currently experience.

Miami’s porous, limestone ground and “booming development” make developing ways to cope with rising seas difficult, a challenge that’s mirrored in the rest of Southeast Florida. The report also singled out Key West, a city whose porous ground and island status leave it with few options for combating sea level rise and the 200 tidal floods it could expect each year by 2045.

“Recognition is growing among residents of famously laid-back Key West that, without concerted action, parts of the city could eventually become unlivable,” the report states.

This isn’t to say that there isn’t hope for these regions. The report lists multiple suggestions for adapting to tidal flooding, including flood-proofing homes and businesses, adopting smart building principles that avoid putting new development in the line of coastal flooding, developing a long term coastal resilience plan and working to reduce city-wide emissions — something the report notes needs to be prioritized by the country as a whole.

Some cities, like Tybee Island, have already started. Baltimore, Maryland, which the report states is likely to experience more than 225 tidal floods a year by 2045, is working to protect its historic regions and lower-income neighborhoods, and has worked climate adaptation into its Disaster Preparedness and Planning Project, which aims to ready the city for future floods and storms.

In Florida, four coastal counties have joined forces in trying to adapt to rising seas. But the report also notes that these localities need help from the federal government, too, in the form of investment, accurate sea level rise monitoring and projections and collaboration with local sea level rise planning.