Rising sea levels are raising the likelihood of more catastrophic tidal flooding in coastal communities during storms, according to a Princeton-based research group’s study. It ranks New Jersey in the top five states most threatened by the rise of sea levels.

Seas are predicted to rise about 15 inches by 2050 in Atlantic City and Cape May. As that happens, storms that used to be considered once-in-a-lifetime events will happen once in a generation, the study said. Seas could rise about a half foot in Cape May and Atlantic City by 2030, the study stated.

The study, titled Surging Seas, illustrates how sea level rise could affect coastal communities based on current census population, existing topographical maps and digital map analysis showing inundation zones by each foot of water above the current average high tide line.

“This is not an ‘if.’ The sea is going to rise, period, end of discussion,” said Richard Wiles, a spokesman for Climate Central. “In the next 15 to 20 years, the odds for serious problems are dramatically increasing. ... People think a couple inches don’t matter, but it’s a huge deal.”

The study looked at every coastal state in the U.S., and noted that Florida and Louisiana have the largest number of people at risk of being affected by sea level rise. New Jersey ranked fifth among the 22 coastal states for the number of people living within a few feet above the current average high water mark. The combination of flooding from storm surges on top of an increased base sea level would put more than 200,000 people and 160,000 homes at risk in New Jersey, the study stated.

Atlantic County also ranks 18th in the nation for the amount of housing below six feet above the mean high tide line, according to the study.

The details of the study also illustrated how each foot of a storm surge would impact the existing South Jersey landscape. A storm surge is the amount of water on top of what would be the predicted tide.

By 2020, there is a one in six chance that there will be a storm surge of four feet above the average high water mark, resulting in severe flooding of the barrier islands in Cape May, Atlantic and Ocean counties, according to the study. As the years progress and sea level continues to rise, the chance for higher floods, such as those when the storm surge reaches five, six and up to 10 feet by 2100, increases to a one in six chance, the study said.

“It’s the storms, it’s your run-of-the-mill northeaster that becomes a more damaging storm,” said David Robinson, state climatologist and Rutgers University professor. “That goes without any real firm knowledge of whether future tropical storms or nor’easters are going to increase in number or in magnitude. We really don’t know.”

Addressing the effects from sea level rise is something that the New Jersey Department of Environmental Protection does consider when issuing permits for projects, such as sea walls, that are expected to be long-lived infrastructure, but the agency does not have any immediate plans other than keeping the topic on the minds of regulators and policy writers, spokesman Larry Ragonese said.

“I think we need to have a good understanding before we can consider any substantial, specific planning for infrastructure along the coast,” Ragonese said. “It’s something we’re aware of and it’s on our plate.”

Storm surges from northeasters, of which the New Jersey coast is prone, differ from surges associated with hurricanes and tropical storms, particularly because there is a limit to how high the water can reach, said Phillip Orton, Doctoral Research Associate at Stevens Institute of Technology in Hoboken. With a northeaster, the storm surge only will reach about six feet, but will last much longer. A hurricane can bring a more localized high surge, but the coastal flooding will last only a short time.

However, Orton said, studies such as the Surging Waters report help the public begin to visualize the impact sea level rise will have as well begin to recognize how local economic conditions will affect how coastal communities fare in the future.

“In places like New York City, they can afford to build up the cities,” Orton said. “When it comes to beaches and marshes and natural coastlines, where there isn’t a lot of money to do beach replenishments, those places will get hurt a lot more. … That’s part of why it’s good they did this study, to look at the whole country more broadly.”

Areas in South Jersey already prone to tidal flooding gradually are seeing an increase in the number of days when certain roads or portions of neighborhoods are flooded, and that effect will gradually increase over the years, said Stewart Farrell, Director of Richard Stockton College’s Coastal Research Center.

“Flooding to the point of nearly permanent inundation of property is a long term problem that has to be faced, either raising everything up by bringing in dirt, or you abandon it,” Farrell said.

And that concept, Robinson said, is something that will make New Jersey’s future unique compared to other states in similar situations because of the value of property.

“New Jersey is going to become a battleground on how to deal with this because there’s so much at stake on the coast,” he said. “The ratables and tourism dollars, it’s so built up that these are the places where these decisions are going to be forged.”

Contact Sarah Watson:

609-272-7216