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3. What is high tide flooding?

**What is high tide flooding?**  “High tide flooding” describes **increasingly common** flooding conditions along the coast due to rising sea levels, sinking land, and the loss of natural barriers. It appears that your browser doesn't support HTML5 video.
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  VIDEO: Flooding isn’t limited to heavy rains. High tide flooding, sometimes referred to as sunny day or nuisance flooding, is a rising problem for coastal communities. Learn how climate change is expected to make the problem worse and how communities are preparing in this video from NOAA's Ocean Today.  Transcript **Adding in Sea Level Rise** NOAA’s Office for Coastal Management offers an online tool to visualize how different local factors, such as strong tides and rainfall, combine to create coastal flooding. You can add sea level rise to the equation and see how much more frequent and severe flooding becomes.
 As relative sea level rises, it no longer takes a strong storm or a hurricane to cause coastal flooding. High tide flooding occurs when sea level rise combines with local factors to push water levels above the normal high tide mark. Changes in prevailing winds, shifts in ocean currents, and strong tidal forces (which occur during full or new moon) can all cause high tide flooding, inundating streets even on sunny days. High tide flooding falls into three levels of severity: minor, moderate, and major. The classifications measure how much water levels exceed average high tide for that location. **Minor** high tide flooding is when water levels reach 0.55 meters (1.8 feet) above average high tide. This minor flooding is mostly disruptive, causing stormwater backups and road closures.
        **Moderate** high tide flooding is 0.85 meters (2.8 feet) above average high tide. This can cause more disruption and can damage homes and businesses.
        **Major** flooding is flooding 1.20 meters (3.9 feet) above average high tide. Floods of this severity are quite destructive, may lead to evacuations, and often require repairs to infrastructure and property. Because of rising seas, land subsidence, and the loss of natural barriers, high tide flooding is now twice as frequent in U.S. coastal communities as it was 20 years ago. Predictions from the latest interagency Sea Level Rise Technical Report show that high tide flooding will become more common and more severe over the coming decades. As sea levels continue to rise, conditions that cause minor and moderate high tide flooding today will cause moderate and major high tide flooding by 2050.
 More **Information** Monthly High Tide Flooding Outlook 2022 Sea Level Rise Technical Report Tidal Flooding Fast Facts NOAA Sea Level Rise Viewer Podcast: Understanding the Sea Level Rise Technical Report   **Search** Our facts    Get **Social** Social
  **Last updated:** 06/01/23 **Author:** NOAA How to cite this article Contact Us


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