What is high tide flooding?

High tide flooding—flooding that leads to public inconveniences such as road closures—is increasingly common as coastal sea levels rise.

high tide flooding events have increased around the U.S., but especially off the East Coast.

High tide flooding events have increased around the U.S., but especially off the East Coast. | Download PDF

As relative sea level increases, it no longer takes a strong storm or a hurricane to cause coastal flooding. Flooding now occurs with high tides in many locations due to climate-related sea level rise, land subsidence, and the loss of natural barriers.

High tide flooding—which causes such public inconveniences as frequent road closures, overwhelmed storm drains and compromised infrastructure—has increased on all three U.S. coasts, between 300 and 925 percent since the 1960s.

The effects of rising sea levels along most of the continental U.S. coastline are expected to become more noticeable and much more severe in the coming decades, likely more so than any other climate-change related factor. Any acceleration in sea level rise that is predicted to occur this century will further intensify high tide flooding impacts over time, and will further reduce the time between flood events.

Perigean Spring Tide

Coastal flooding as seen at Hains Point, Washington D.C. on September 26,2015.

During a perigean spring tide, those areas that normally experience frequent high tide flooding may see even higher levels of inundation with longer duration. In this image, a perigee moon coincides with high tide to cause coastal flooding conditions at Hains Point, Washington D.C. on September 26, 2015.