The dangers to Washington are acute, the report said. Contrary to popular myth, the city was not built in a swamp, but it is in a flood plain, and its officials and engineers have tamed the wild Potomac. Those advances could be turned back as the seas rise, the report said. And that may affect the nation well beyond the District of Columbia’s boundaries.

“The monument area and the Mall are in some ways the soul of Washington, D.C., so to see those areas flooding, I think, will probably have an important emotional and cultural effect, as well as a physical effect,” said Ben Strauss, director of Climate Central’s Program on Sea Level Rise and the report’s lead author. A sea-level increase of about four feet by the end of the century would most likely lead to at least one damaging flood more than eight feet above high tide, the study says. The current record of 7.9 feet was set in 1942.

The study’s lowest estimate, which accounts for a rise in the sea level of just one and a half feet, predicts flooding more than six feet above high tide in just 16 years, akin to some of the most severe floods the city has seen. Just four floods have exceeded six feet since 1931.

“You could go from a situation where you buy a home, it’s never been flooded before in memory, it’s a low flood risk,” Mr. Strauss said. “And by the time you pay off your mortgage, it’s getting flooded every single year.”

The group also released analyses of the risks facing Delaware, Maryland and Virginia, and some of the most troubling findings show how climate change will affect military installations, Mr. Strauss said.