As sea levels rise across the coastal U.S., flooding, specifically high tide flooding, is becoming increasingly more common. With climate change expected to continue driving sea level rise and flooding events, water and wastewater utilities along the coast are encouraged to start planning to mitigate and respond to these types of contingencies.

With sea levels rising across the U.S., high tide flooding can occur in the absence of heavy rainfall or storms. Consequently, 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 research by Climate Central. And besides high tide flooding, rising sea levels can inundate low-lying wetlands and dry land, erode shorelines, contribute to coastal flooding, and increase the flow of salt water into estuaries and nearby groundwater aquifers, according to the EPA. As previously mentioned, flooding is becoming more frequent along the U.S. coastline. However, the U.S. Gulf and Southeast coasts have experienced some of the highest increase in sea levels, with the ocean rising an average of 6 inches since 2010, one of the fastest such changes in the world, according to a Washington Post analysis.

And with sea level rise, the number of high-tide floods is rapidly increasing in the U.S. Gulf and Southeast coastal region, with incidents happening five times as often as they did in 1990, said William Sweet, an oceanographer for the National Oceanic and Atmospheric Administration (NOAA). The Washington Post analysis also determined there are now more dangerous rain-driven and flash floods reported within 10 miles of the coast in the region. Flooding events increased by 42% from 2007 to 2022, with a total of 2,800 events, according to a Post analysis of National Weather Service data. Despite the rising sea levels and associated flooding events, many communities along the coast are working now to construct hazard mitigation infrastructure. In Galveston, Texas, for example, local stakeholders are planning to install several large pump stations in the coming years, largely funded through federal grants. Read more at Climate Central and read a special three-part series report on sea level rise from the Washington Post (Part 1, Part 2, Part 3).

For more information on hazard mitigation related to sea level rise and high tide flooding, visit this Climate Resilience Toolkit page.

And for more information on sea level rise at a community level, visit this NOAA Sea Level Rise Viewer tool page.

WaterISAC also encourages members to review the EPA resource, "Flood Resilience: A Basic Guide for Water and Wastewater Utilities," which is an important guide to help utilities understand their flooding risk and identify practical mitigation options to protect your critical assets.