This is a city of rivers and creeks, and while no neighborhoods had been ordered to evacuate by Monday afternoon, concerns about flooding from the advancing Hurricane Sandy led to pleas to residents to take shelter on high ground.

“Part of the challenge for us has been to strike an appropriate balance between nonchalance and utter horror and fear,” Mayor Michael Nutter (D) said at a briefing in West Philadelphia, where the local high school has been transformed into an AmericanRed Cross shelter.

“If you looked outside this morning, you might think, ‘It’s not so bad,’ ” Nutter said. “All we can stress is, it’s going to get progressively worse.”

An estimated 10,000 city residents live in areas at risk of serious flooding. Rain and winds forced evacuations in some nearby suburbs to guard against storm surges from the Delaware and Schuylkill rivers, which are expected to flood.

“We have two rivers and a full moon,” Nutter said.

Philadelphia declared a state of emergency, shutting down its schools and mass transit system, and hundreds of flights were canceled at the city’s airport. Fifteen thousand members of the National Guard have been told to be ready for deployment, officials said.

About 140 people had turned up at West Philadelphia High School seeking shelter as of 1 p.m. Monday, the Red Cross said. Among the cots spread across the gymnasium floor were five cats and 21 children.

Lamont Smith, a 27-year-old unemployed landscaper, lives a block from Cobbs Creek, a routinely flooded waterway in much smaller storms. The back room in his apartment was already starting to leak from the rain. He was out walking Monday morning when he heard about the shelter.

“As soon as I came in, they made sure I ate,” he said.

Garrett Tate was visiting the city Sunday and discovered that his New Jersey Transit bus home to Atlantic City was canceled. So he went to the shelter — and feels relieved.

“It’s a very humble feeling here,” said Tate, who is 56 and sells pinball machine parts to the arcades on the boardwalk. “They want to help you here. With no agenda.”

He was given three blankets and a toiletry kit with soap and toothpaste.

The lights were on in some corner stores in the neighborhood of rowhouses, many of them boarded up, as customer ran in for last-minute provisions and lottery tickets. But by mid-afternoon workers were pulling down their corrugated doors to close.

Many communities in West Philadelphia, the sprawling tracts across the Schuylkill from the city center, remain mired in poverty, blight and crime. Some residents seemed resigned to losing power and having the storm disrupt their lives.

“If it happens, there’s nothing we can do about it,” said Angela Holt, 47, on her day off from her nursing home job in the suburb of Bryn Mawr. “Frankly, I don’t think it’s going to be as bad as everyone says.” Holt was doing laundry and not fretting.

She was one of four customers all day at the Philly Wash on Chestnut Street. Manager Tony Foreman, in a blue Phillies cap and sweatpants, a diamond stud in his left ear, opened the laundromat at 6 a.m.

“My boss wanted me to stay open to see if we were going to get business,” he said. Business was so slow that by 10 a.m. he called the boss and said he wanted to close, but the boss told him to wait it out.

Above him a red sign hung from the ceiling: “Giant Load: $6.95.” Philly Wash still has a working pay phone and a prominent sign that says, “The laundromat is monitored by a video camera, 24 hours.”

By 2:30 p.m. Foreman got the go-ahead to close up and wait out the storm in his apartment down the street.

“It’s unclear if we’ll be open tomorrow,” he said.