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.
The Broad Channel community is a proactive one. After more than a decade of lobbying by the Broad Channel Civic Association, the City of New York has funded and begun work on a $23 million project to enable West 11th, 12th, and 13th Streets to withstand and avoid flooding. Measures to make critical services more resilient, including the power supply, wastewater treatment, health care, and transportation, are also under development. The communities of Jamaica Bay—with partner agencies and organizations—are charting a path to urban coastal resilience that others around the country can build on.
In the long run, we will need more concerted action to avoid the worst impacts of sea level rise by ultimately reducing our heat-trapping emissions. But in the short term, the many other communities that will join the front line of tidal flooding will need to learn from the experience of Jamaica Bay and be able to adapt and response to the rising tides.
Tidal flooding can occur when high tide exceeds the normal level by about one to three feet, depending on the location. Minor, or nuisance, flooding, as determined by the National Weather Service, can disrupt local transportation and daily life. Moderate flooding is more extensive and can threaten life and property. This latter type of flooding usually occurs when a high tide combines with a storm system. As sea levels continue to rise, typical high tides will exceed these thresholds more often.