Tidal flooding in the U.S., in 2014, and projected to the years 2030 and 2045. Of the 52 locations we examined, 30 (shown here) can expect at least two dozen tidal floods per year, on average, by 2030. By 2045, one-third of the locations we analyzed can expect 180 or more tidal floods per year. And nine locations could average 240 or more tidal floods a year by 2045. Graphic: UCS Encroaching Tides Report 2014

By Melanie Fitzpatrick
17 October 2014 (UCSUSA) – What would it be like to live in a place that floods every full moon? We asked that question and others in our report, Encroaching Tides, which was released last week. During that week, there was a perigean spring tide – an extra-high tide when the sun, moon, and Earth are aligned and the moon is closest to Earth in its monthly orbit. This alignment happens three or four times a year. In many locations along the U.S. east coast, these extra-high tides – colloquially known as “king tides” – brought flooding last week to places like the Florida Keys, Charleston, Annapolis, and Washington DC. These events give us a glimpse into the future, as I outlined in an earlier blog on king tides. Our analysis shows that this kind of tidal flooding could become the new normal in many places in the next 15 years under a global sea level rise of about 5 inches by 2030 and 11 inches above today’s levels by 2045. (You can find the technical background study outlining the mid-range scenario we used here. For news coverage of our report, see articles here, here, and here.) NOAA studies have shown that in several communities, nuisance flooding now happens four times more often than it did just 40 years ago. In the next 15 years, two-thirds of the communities we analyzed could see a tripling or more in the number of high tide flood events each year.

The case study of Jamaica Bay, New York

We know that many places are already on the front line of tidal flooding – places like Jamaica Bay, New York, which we profile in the report. Over the last century, the water level in Jamaica Bay (as measured at the nearby Battery tide gauge) has risen nearly a foot, owing to both global sea level rise and local changes. Minor flooding events in the Broad Channel area now occur once or twice a month, or more. And our analysis shows that continued sea level rise means that the frequency of flooding events in Jamaica Bay will triple by 2030, and increase nearly 10-fold by 2045, compared with today. Dan Mundy, Sr., former president of the Broad Channel Civic Association and a retired captain in the New York City Fire Department, knows that flooding is becoming worse. “Every home in Broad Channel has a calendar with the lunar cycle and tide predictions clearly marked for each day of the year,” he says. “We live by the tidal cycles here: flooding is becoming more common, and much more of an inconvenience than ever before.” Volunteer firefighters at the Broad Channel Fire Department know which streets might need evacuation by inflatable boats. [more]

As Sea Level Rises in Jamaica Bay, New York, Tidal Flooding Moves from Occasional to Chronic