America’s trillion-dollar coastal property market and public infrastructure are threatened by the ongoing increase in the frequency, depth, and extent of tidal flooding due to sea level rise, with cascading impacts to the larger economy. Actions to plan for and adapt to more frequent, widespread, and severe coastal flooding would decrease direct losses and cascading economic impacts.

Source: Chapter 8 of the Fourth National Climate Assessment



The map shows the relative risk as sea level rises using a Coastal Vulnerability Index calculated based on tidal range, wave height, coastal slope, shoreline change, landform and processes, and historical rate of relative sea level rise. {Data sourced from Hammar-Klose and Thieler 2001, figure available in the NCA3}.

Every year, at multiple locations along the coast of the United States, events such as storm surges, high tides, strong waves, heavy precipitation, increased river flow, and tsunamis cause damaging coastal floods. As global sea level rises, higher water levels will exacerbate the impacts of these incidents, resulting in deeper floods that last longer and extend further inland.

Additionally, as climate changes, some coastal hazards are projected to increase. For instance, coasts may see more severe or more frequent storms and heavier rainfall events. Observed global mean sea level rise for 1900 to the present, and projected global mean sea level rise for four scenarios from the present to 2100. Average global sea level rose eight inches during the last century, and scientists are highly confident that it will continue rising in the future. By 2100, global sea level is projected to be between 8 inches and 6.6 feet higher than it was in 1992. At regional and smaller scales, relative sea level is also affected by vertical land movement and ocean currents, but any amount of global sea level rise will increase the frequency and magnitude of coastal flooding impacts, posing an increasing threat to people, infrastructure, and coastal economies (Source: U.S. Climate Resilience Toolkit).

As of 2013, coastal shoreline counties were home to 133.2 million people, or 42% of the population. The coasts are economic engines that support jobs in defense, fishing, transportation, and tourism industries; contribute substantially to the U.S. gross domestic product; and serve as hubs of commerce, with seaports connecting the country with global trade partners. Coasts are home to diverse ecosystems such as beaches, intertidal zones, reefs, seagrasses, salt marshes, estuaries, and deltas that support a range of important services including fisheries, recreation, and coastal storm protection. U.S. coasts span three oceans as well as the Gulf of Mexico, the Great Lakes, and Pacific and Caribbean islands (Source: Chapter 8 of the Fourth National Climate Assessment).

Guiding Concepts
  1. What areas currently are at greatest risk of coastal flooding?
  2. What areas are going to be impacted in the future as sea level rises?
  3. In what areas are there additional factors that add to the risk?
  4. Where are vulnerable populations, infrastructure, and sectors in relation to the flooding risk areas?
  5. What analyses can be done to quantify current and future potential impacts?
  6. Can we quantify how natural and built environments can contribute to resilience to coastal flooding?

Explore more Coastal Flooding resources here:
Updated on May 17, 2021