Key concepts
- As sea levels rise, flooding is becoming more common along U.S. coasts, where about 30% of the population lives.
- High tide flooding can occur in the absence of heavy rainfall or storms, and the effects can be disruptive, dangerous, and costly for coastal communities.
- The annual frequency of high tide flooding in the U.S. has more than doubled since 2000 — and is projected to more than triple again by 2050 as sea levels continue to rise.
- According to NOAA outlooks for 2023, the annual risk of high tide flooding is expected to peak during late September and October in many locations along the East and Gulf Coasts.
Coastal communities face more floods
In our warming climate, it no longer takes a strong storm to flood streets, homes, businesses, and ecosystems along the coast.
— also called nuisance flooding or sunny day flooding — is becoming more common in the U.S., where lives in coastal counties.
As global sea levels rise, water levels along the coast rise too. As daily tides cycle over higher baseline water levels, high tide lines migrate farther inland or upslope — regularly flooding coastal areas that previously would have flooded only during storms or extreme rainfall events.
High tide flooding happens when water levels exceed 1-2 feet above the daily average high tide (the threshold for minor high tide flooding).
High tide flooding: disruptive, dangerous, and costly
Such flooding can clog storm water drains, flood streets, inundate coastal infrastructure and ecosystems, and affect freshwater supplies.
These impacts worsen during so-called , the highest astronomical tides of the year. Flood risks compound if extreme high tides also overlap with heavy rains or storms.
Earlier this year, NOAA released a new interactive that shows how likely high tide flooding is on each day of the year at 98 coastal U.S. locations.
According to NOAA outlooks for 2023, the annual risk of high tide flooding is expected to peak during late September and October in many locations along the East and Gulf Coasts.
Warming planet, rising seas, flooding coasts
The oceans absorb caused by carbon pollution. As , the volume of seawater expands — causing sea levels to rise. Melting glaciers and ice sheets also contribute to rising sea levels.
Global mean sea level rose 7.8 inches from 1901 to 2018, according to . Sea levels have been rising faster since the late 1960s, and .
Sea level rise is accelerating along U.S. coasts. According to NOAA, sea levels along U.S. coasts are expected to rise as much (10-12 inches, on average) as they did over the last 100 years.
Rising sea levels have contributed to the increased frequency of coastal flooding in the U.S. — especially in the last two decades.
More high tide flood days in the U.S.
The annual frequency of U.S. high tide flooding . Flood frequency is projected to more than triple again by 2050 (relative to 2020) to reach a national average of .
The Northeast, Southeast, and Gulf Coasts have experienced the largest historical increase in high tide flooding.
Last year, saw record or record-breaking numbers of high tide flood days, including in Florida, Puerto Rico, Virginia, Georgia, and Washington state.
A strengthening could further along due to regional effects on storms and sea level.
Coastal flooding: not only a coastal issue
The latest science is clear: we can expect more coastal flooding far into the future, .
In the absence of measures to both rapidly curb emissions and reduce risk, coastal flood impacts are likely to become increasingly damaging and destructive.
People, ecosystems, and infrastructure along the coast will be directly affected by flooded homes, streets, and businesses, erosion, stormwater overflows, and reduced water quality.
But such impacts along can have far-reaching effects.
U.S. coasts are essential for trade and supply chains we all depend on. They’re home to large and growing populations. Recreation, tourism, and fisheries are all thriving coastal industries. And ecosystems such as provide coastal protection, wildlife habitat, and carbon storage.
Thus, the entire country is directly or indirectly affected by the inundation of our coasts as sea levels continue to rise.
Reversing recent trends ultimately requires rapid and sustained emissions cuts. But even under , sea levels will continue to rise.
Ways that coastal communities can to future flooding include raising roads, stabilizing shorelines, relocating low-lying buildings, and restoring coastal ecosystems.
Local story angles
What’s the flooding outlook in your local area?
±·°¿´¡´¡â€™s and High Tide Flooding Outlooks show when and where high tide flooding is most likely in 98 coastal U.S. stations, to guide seasonal planning and preparedness. The Annual Outlook also provides local high tide flooding projections for 2050. Both outlooks are integrated into ±·°¿´¡´¡â€™s which provides 48-hour forecasts and local images of recent floods. The National Weather Service provides real time .
What’s at risk in your nearest coastal area?
Use ±·°¿´¡´¡â€™s to explore, visualize, and download data about flood hazards, sea level rise, and the marine and coastal economy in 850+ coastal counties across 37 coastal states and territories. Go deeper with ±·°¿´¡´¡â€™s to locate people, infrastructure, and ecosystems exposed to flood hazards along U.S. coasts. Use Climate Central’s and tools to explore local risk and visualize how 190 landmark sites would be affected under different warming scenarios.
How are sea levels and coastal floods changing in your area?
The from NASA and NOAA provides sea level rise projections for each decade through 2150 for: the entire U.S., major coastal regions, and individual tide gauge stations along the coast. Use , part of the U.S. Climate Resilience Toolkit, to chart in your city. Climate Central’s can be used to map areas at risk from sea level rise and coastal flooding under a range of warming scenarios. Use
Contact experts
Kate Silverstein (she/her/hers)
NOAA National Ocean Service
Can connect to experts on: Sea level rise and coastal flooding
Contact: [email protected], [email protected]
For questions about Climate Central’s suite of sea level rise tools, please contact: Kelly Van Baalen, project manager, at [email protected].