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The poorer sections of the city are always a worry, said Council member Marion Barry, the former four-term mayor. He represents Ward 8 — the poorest of the city’s wards — and said his constituents were accustomed to bearing the brunt of bad weather and other adversity.

“Whenever there’s an outage, we’re going to be the first,” Mr. Barry said. “We’re the first, and we get hit the hardest.”

Homes in Ward 8, however, are unlikely to be flooded by a surging Anacostia River, because the riverfront is occupied by a park and by Bolling Air Force Base.

Much of official Washington has considered the possibility of a once-in-a-generation storm.

For example, the monuments along the Tidal Basin — including the Jefferson Memorial and the new King Memorial — are designed to withstand flooding, said Bill Line, a National Park Service spokesman.

Mr. Line said he did not believe the Tidal Basin — a manmade inlet off the Potomac River walled off by a stone embankment — had ever overflowed its banks, although he conceded it was possible in an incredible storm surge. Much of the National Mall was created by a massive Army Corps of Engineers dredging project more than a century ago that altered the path of the Potomac River. There was not damage by Saturday night.

The National Archives installed self-rising walls to protect the building after severe flooding in the basement damaged a newly opened theater, said spokeswoman Susan Cooper. The walls have worked in past storms, she said. The building doesn’t keep its precious documents in the basement.

Pepco, the utility serving the district and its Maryland suburbs, warned customers that Irene could bring destruction and that restoring service could take several days.

Millicent West, the city’s homeland security director, said officials from several agencies would be making the rounds in poor neighborhoods to make sure residents weren’t neglected. Mayor Vincent C. Gray said that given forecasts showing the storm moving out by Sunday afternoon, he did not anticipate vulnerable residents being isolated for days in dangerous conditions.

“We hope that the duration of this will be relatively short, which means that people can get back out and get engaged in the normal patterns of life,” Mr. Gray said.

Ward 8 has a 25 percent unemployment rate and a 35 percent poverty rate. In Anacostia, some residents were making do with what they had, which wasn’t much.

“I’m just about as ready as I can get,” said Patricia Williams, a resident of Barry Farm, a sprawling, rundown public housing complex. “I don’t have no money to stock up on water and food.”

• Associated Press writer Eric Tucker contributed to this report.