As many as 21 New Jersey communities face "chronic inundation" — flooding an average of every other week — within two decades under a scenario experts consider an intermediate level of sea rise, according to a peer-reviewed study by the Union of Concerned Scientists.

"By 2100 in this scenario, more than 100 New Jersey communities would experience chronic inundation—second only to Louisiana," the report states.

"We were surprised at the findings for New Jersey," said Erika Spanger-Siegfried, a lead author of the report.  She is a senior analyst in the climate program at the Union of Concerned Scientists, a nonprofit advocacy organization.

Spanger-Siegfried said she expected to see many areas in Louisiana and along the Eastern Shore of Maryland pop up as vulnerable because of their geography and low population densities, but New Jersey was more of a surprise.

The study "flagged for us that there's a large sea-level rise risk flying under the radar for New Jersey, and it's not going to take a great deal of sea-level rise to impact communities there," Spanger-Siegfried said.

She noted that some New Jersey communities, such as West Wildwood, are already strengthening bulwarks against sea rise.  West Wildwood was one of the areas projected to be hit hardest by 2035, she said, with much of its small landmass subjected to chronic flooding.  But the data were assembled before the community installed better flood protections, she noted.

The average sea level has risen about eight inches globally since 1880, but actual levels depend on geography. The East Coast has experienced some of the fastest rates in part because some of the land is sinking.  More water just hastens the rise.

Recent reports by the National Oceanic and Atmospheric Administration and Rutgers and Princeton Universities on such flooding have also noted the impact on New Jersey.

Wednesday's report by the Union of Concerned Scientists also has a separate fact sheet for New Jersey.  There is also an interactive map to let a user drill down to specific areas.