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 in the U.S. on average by about 50 percent since 20 years ago and 100 percent since 30 years ago.
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.
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.