Some Coastal U.S. Cities Could Experience Flooding Every Day by 2100 If Sea Levels Rise as Expected, Scientists Say

By 2100, city streets in some coastal U.S. cities could experience flooding every day, making urban waterfronts practically uninhabitable, if sea levels continue to rise as expected.

Extreme flooding events in some coastal areas of the country could double every five years, according to a study published in the journal Scientific Reports.

For their research, a team of scientists from the U.S. Geological Survey (USGS,) the University of Illinois at Chicago (UIC) and the University of Hawaii, examined data on water levels along the U.S. coastline and compared this with sea level rise projections.

In the study, they predict that today's "once-in-a-lifetime" extreme water levels, which are currently reached every 50 years, may be reached every year in 70 percent of U.S. coastal regions by 2050, and every day at high tide for 90 percent of the U.S. coastline based by 2100, based on well-established sea-level projections.

Furthermore, the scientists found that the chances of extreme flooding increases exponentially with sea-level rise.

"For most locations around the U.S., we found that 5-10 centimeters [around 2-4 inches] of sea-level rise can double the chances of flooding. Combining this with sea-level projections over time, it appears that the chances of extreme flooding most locations around the U.S. will double every 5-10 years," two authors of the study, Mohsen Taherkhani from UIC and Sean Vitousek with the USGS, told Newsweek.

"The idea that sea-level rise increases coastal flooding is not entirely new. This concept has been around for several decades. However, with this paper, we have sought to analyze and communicate this in the most straightforward way possible, via a doubling time scale, which we found to be about 5 years," they said.

According to the researchers, cities in low latitude, low-elevation regions will be the most vulnerable, such as, Honolulu; Galveston, TX; New Orleans; and San Diego, Los Angeles, and San Francisco.

They added that some cities along the east coast—such as Miami, Charleston, Norfolk, and Atlantic City—were "highly vulnerable."

flooding, Florida
Katie Pettit uses a boat to navigate through a flooded street on December 23, 2019 in Hollywood, Florida. Joe Raedle/Getty Images

"Many of these cities are currently subject to nuisance-level flooding during king tides [exceptionally high tides]—with several inches of water covering and closing roads," the authors said. "If sea-level projections hold and in the absence of adaptation by 2050, this flooding will become much more widespread, frequent, and severe."

"By 2050, it would likely mean widespread disruption of transportation due to road closures during spring tides [those after a new or full moon.] By 2100 with 1.0-2.0 meters [3.2-6.6 feet] of sea-level rise, city streets would likely be flooded every day during high tide, making urban waterfronts practically uninhabitable," the authors said. "However, even before this point, large storm events plus sea-level rise would likely exceed the infrastructure's design conditions resulting in wide spread damage."

The researchers say that if the world was able to curb emissions of greenhouse gases sufficiently, we may be able to effectively delay the impacts of coastal flooding by decades, giving the nation more time to adapt.