Coastal flooding set records in the United States last year, increasing the challenge to Fort Lauderdale, Miami Beach and other South Florida cities where high tides can inundate low-lying neighborhoods.
The National Oceanic and Atmospheric Administration issued a report Wednesday that said rising sea levels and frequent storms set flood records across the country in 2017 — and warned that 2018 could be worse.
“As relative sea level increases, it no longer takes a strong storm or a hurricane to cause coastal high tide flooding,” stated the agency’s report. “High tide flooding causes frequent road closures, overwhelmed storm drains, and compromised infrastructure.”
Taking into account the sea-level rise of the past few decades and the periodic El Niño warming of the eastern Pacific Ocean, the agency predicted that 2018 would see coastal flooding continuing to be a far worse challenge than it had been in the past.
“The projected increase in high tide flooding in 2018 may be as much as 60 percent higher across U.S. coastlines as compared to typical flooding about 20 years ago and 100 percent higher than 30 years ago,” the report said. “This is due to long-term sea level rise trends and, in part, by El Niño conditions that may develop later this year.”
Coastal flooding has been a growing problem in South Florida, where the arrival of high annual tides called king tides sends water into the streets, even on sunny days. Among the most vulnerable areas are the East Las Olas Boulevard neighborhoods of Fort Lauderdale, the Lakes section of Hollywood, much of Miami Beach and the Marina Historic District of Delray Beach.
Cities have been investing billions in adapting to rising sea levels, from improved sewer systems to revised building codes.
Fort Lauderdale has installed 147 one-way valves to prevent tidal water from bubbling up storm drains, raised a sea wall, cited property owners with inadequate sea walls, planned the elevation of other city-owned sea walls and sealed failing stormwater pipes, said Nancy Gassman, assistant public works director.
“Sea level will continue to rise, and so adapting to it will be something that we will need to commit to for the rest of time,” she said. “Some of these neighborhoods are like buckets with holes in them, and the city is working very diligently to identify those gaps and to plug them.
“Whether it’s problems with water coming up our storm drains or it’s a problem with seawater coming over private property sea walls, we’re working toward sealing up those holes to try to provide an environment that has a reduced flood risk and that the intensity, duration and frequency of flooding are reduced.”
In preparing its flooding report, NOAA studied data from 98 tide gauges, some in place for more than a century, and concluded that coastal flooding was worsening and that sea-level rise was a major factor. Among these were six tide gauges in Florida, including one at Key West and another at Virginia Key, just off downtown Miami.
“By looking at this long-term data record, we can see how the flooding that used to only occur during major storms and maybe once in a decade, now occurs with regularity, four five times a year,” Greg Dusek, chief scientist for NOAA’s Center for Operational Oceanographic Products and Services, said in a telephone news conference.
Sea-level rise is driven by global warming, caused by the buildup of heat-trap gases in the atmosphere from vehicle exhaust pipes and industrial sources. Sea levels are rising at about an inch every eight years, with about two-thirds of the increase coming from melting glaciers and the rest from the expansion of water as it warms, said William Sweet, a NOAA oceanographer, in the conference call with reporters.
Particularly vulnerable is the southeastern United States, the report said, where flat geography allows water to reach farther inland.
“The southeast Atlantic coast is currently experiencing the fastest rate of increase in annual high tide flood days, with more than a 150 percent increase since 2000 predicted in 2018 at most locations,” the report said.
Flooding will be most common in the fall, when there are the highest seasonal high tides.