Patterns and Projections of High Tide Flooding Along the U.S. Coastline Using a Common Impact Threshold

The National Oceanic and Atmospheric Administration (NOAA) analyzes "high tide flooding" (also known as "nuisance flooding") in this report, and finds that it is becoming more commonplace due to sea level rise. High tide flooding impacts roads, beaches, parks, and private property, and is generally more disruptive than damaging. However, there are places such as Norfolk, Virginia; San Diego, California; and the U.S Marshall islands where it is currently a serious problem. Even more, with continued sea level rise, flooding is likely to increase. By 2100, NOAA predicts that high tide flooding will occur every other day or more in the Northeast and Southeast Atlantic, the Eastern and Western Gulf, and the Pacific Islands. Essentially what we call a flood today will become the new high tide in nearly all regions. The report recommends that future flood frequency is considered when determining building standards. 

The findings in this report are supported by a methodology relying on information from tidal gauges maintained by NOAA. Using these tide gauges, NOAA has been able to document a rapid and accelerating change in annual frequencies of tidal flooding. Rather than simply describing flood risk, this report aims to "derive a nationally consistent definition of coastal flooding and impacts used in quantifying and communicating risk." Part 2 outlines the researchers' considerations and primary findings. Using statistical regression they find a set of flood threshold proxies that can be used to identify minor, moderate, or major flooding impacts for almost any location in the United States. 

Part 3 of the report describes trends in high tide flooding. Flooding has increased the most along the Atlantic Coast. Along the West Coast, high tide flooding has been much more consistent over time, except for a few locations including San Diego, Los Angeles, Humboldt Bay, and Seattle. While the trends consistently show increases in high tide flooding in many regions, the authors emphasize that the number of flood events can vary substantially year-to-year due to weather vulnerability and El Niño patterns. In order to properly prepare for flooding, regions should understand the seasonal cycles of high tide flooding. For example, in San Diego flooding is most likely in June-July or December-January. In non-tidally driven locations, such as the Chesapeake Bay, flooding may occur less predictably. 

Part 4 specifically looks at future risks and the impacts of sea level rise. While flooding is expected to increase across the U.S. coast, some places, such as New York City, will see a faster increase. The report describes the expected increase in flood events by region. By 2100 the Northeast Atlantic can expect flooding in 235 out of 365 days a year. 


Publication Date: February 2018

Authors or Affiliated Users:

  • William Sweet
  • Greg Dusek
  • Jayantha Obeysekera
  • John Marra

Related Organizations:


Resource Category:

Resource Types:

  • Assessment
  • Climate science

States Affected:


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