A federal agency that studied the Fox Point hurricane barrier this spring has found that Providence is safe until 2100.

The barrier was built across the Providence River after the hurricane of 1938 and Hurricane Carol in 1954, and finished in January 1966. According to the study, it is "robust against future coastal storms" and rising seas "to 2100." The agency does not expect water to come over the top until the 2130s, and then only under its highest sea-level scenario.

What the agency expects instead is for the gates to close. The river gates shut when the water outside reaches a set height. Since 2022 that has happened between zero and three times a year. Under the agency's high scenario it happens 357 days a year by 2100. Under the intermediate scenario, 128.

A barrier that is closed 357 days a year is a wall. The river still arrives from upstream, and when the gates are shut it has to be pumped out. The pumps move 7,000 cubic feet a second. The agency modeled heavier rain and found that, with the gates closed, the water "will accumulate further upstream" and "likely cause flooding."

The agency considered a new barrier and found it "likely unnecessary." It recommends changing the operating manual. One option it describes is raising the height at which the gates close, so they close less often. That, it says, "may expose the areas behind the barrier to residual damages and nuisance flooding," which can "likely be mitigated" by "elevating or floodproofing critical infrastructure or private property."

So the city has two choices. It can live behind a wall that is shut every day of the year except eight. Or it can open the wall and raise the houses.

Either way, Providence is safe until 2100. All it has to do is live underwater.