Sea level rise is causing record-breaking coastal flooding. It's only expected to get worse – even on days without rain.
The nation's coasts are in trouble. After a year of record-breaking coastal flooding, a new report released by the National Oceanic and Atmospheric Administration found that it's going to get more frequent, more intense and more widespread across the U.S.
High-tide flooding, otherwise known as "king tides" or "sunny day" flooding, has already increased in frequency over the years as sea levels continue to rise. According to NOAA, it typically occurs when tides rise about 2 feet above the daily average and ocean water starts to cascade over streets and bubble up from storm drains.
This kind of flooding used to really only happen during storms. But now, NOAA says it can happen just from a full moon or a shift in prevailing winds or currents. Decades of sea level rise is to blame and the situation has only been driven by climate change.
"The East and Gulf coasts already experience twice as many days of high tide flooding compared to the year 2000," Nicole LeBoeuf, director of NOAA's National Ocean Service, said, "flooding shorelines, streets and basements and damaging critical infrastructure."
Some communities are already feeling the toll of the growing situation.
Reedy Point, Delaware, has already experienced six days of high tide flooding since January, one day more than it saw in 2021. Springmaid Pier, South Carolina, has tied its 2021 record with 11 days of flooding. Kwajalein Island, in the Pacific's Marshall Islands, also surpassed its 2021 high tide flooding events.
Scientists say La Niña is what prevented coastal areas from experiencing a record-breaking number of floods in 2022. But overall, the conditions are only accelerating.
NOAA's latest report, published on Tuesday, outlined the agency's "increased confidence" that the nation is going to feel the wrath of sea level rise sooner rather than later. Over the next 30 years, the agency said, the relative sea level along the contiguous U.S. coastline is expected to rise, on average, nearly 2 inches — the same amount it rose over the last 100 years.
By 2050 — just 28 years from now — NOAA anticipates that "national scale high tide flooding" will last between 45 and 70 days. And it's not just the number of floods that has scientists concerned, it's also the intensity. Within the next three decades, experts say major and moderate flood events will happen as frequently as moderate and minor flood events occur today.
Major coastal high tide flooding, which is often destructive, will likely increase from 0.04 events per year in 2020 to 0.2 events in 2050 — a 400% increase.
Without taking steps to reduce the impact, NOAA says in the report, the nation "will face significant consequences" ranging from damaged communities and overloaded stormwater and wastewater systems to stressed coastal ecosystems. Along with implementing more resilience strategies in coastal areas, NOAA said global warming as a whole must be curbed to prevent the worst outcomes.
If the world hits 2ºC of global warming compared to pre-industrial levels, it's expected that oceans will rise more than 1.5 feet globally and more than 2 feet around the contiguous U.S. Currently, NOAA says, the probability of that happening by 2100 is about 50%. More greenhouse gas emissions, which fuel global warming, only increase that probability.
"The amount of sea level rise is strongly affected by future global warming," the report says. "By reducing greenhouse gas (GHG) emissions, severe and transformative impacts occurring later this century or early next century along U.S. coastlines are more likely to be avoided. As GHG emissions and global temperatures continue to rise, the likelihood of very high U.S. sea level rise does too."
