High Tide or “Sunny Day” Flooding Expected to Increase in Maryland, Other Coastal Areas

Bay Journal article (2019-07-15) examined a new National Oceanic and Atmospheric Administration (NOAA) report showing that the Chesapeake Bay watershed is particularly susceptible to increased “sunny day” or high tide flooding (HTF). HTF does not occur due to rainfall but is based on other climate factors interacting with a high tide. According to the report, HTF “can now happen when a steady breeze or change in coastal current overlaps a high tide.” The report found that rising sea levels will increase the amount of HTF in Maryland.

From the NOAA report:

Tide gauges of the U.S. National Oceanic and Atmospheric Administration (NOAA) are measuring rapid increases in coastal flood risk along U.S. coastlines due to relative sea level (RSL) rise. The most noticeable impact of RSL rise is the increasing frequency of high tide flooding (HTF) that in 2018 was 1) disrupting vehicular traffic along the U.S. East Coast due to flooded roadways, 2) inhibiting parking and thus slowing commerce at stores in downtown Annapolis, Maryland, 3) raising groundwater elevations and degrading septic system functionalities in South Florida, and 4) salting farmlands within coastal Delaware and Maryland.

HTF causes traffic disruptions, infrastructure damage, and saltwater intrusion farmland. From the Bay Journal article:

The problem was worse in the Northeast, which includes the Chesapeake watershed. The report, released on July 10, showed this region with a median of 10 days of high-tide flooding. The following Chesapeake-area cities carved out new records:

  • Washington, DC, 22 days
  • Lewisetta, VA, 15 days
  • Annapolis, MD, 12 days
  • Baltimore, 12 days …

“Once communities realize they are susceptible to high-tide flooding, they need to begin to address the impacts, which can become chronic rather quickly,” said William Sweet, a NOAA oceanographer and lead author of the report. “Communities find themselves not knowing what to expect next year and the decades to come, which makes planning difficult. Our high tide projections can play a vital role in helping them plan mitigation and other remedies.”

Useful Links

2018 State of U.S. High Tide Flooding with a 2019 Outlook (NOAA)

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