NEW ORLEANS (AP) — Authorities say storm surge driven by Hurricane Isaac has overtopped a levee in a thinly populated part of Plaquemines Parish, south of New Orleans.

Parish spokesman Caitlin Campbell said an 18-mile stretch from the St. Bernard Parish line at Braithwaite south to White Ditch was taking water and homes were flooding.

An evacuation order had been issued as Isaac approached. Sheriff’s deputies from St. Bernard and Plaquemines parishes were going house-to-house getting residents who’d remained in the area to move to higher ground.

Campbell said streets in the area were still passable.

Parish President Billy Nungesser said a portion of the roof of his home in on the parish’s west bank had blown off. He described wind-driven driven coming into his home as “like standing in a light socket with a fire hose turned on.”

Elsewhere, the storm drove sheets of rain through the nearly deserted streets of New Orleans as a population mindful of the powerful punch dealt by Katrina seven years ago waited for the storm to get out of their lives. Isaac had stalled along the coast early Wednesday before resuming a move to the northwest several hours later.

Forecasters said the storm could drop up to 20 inches of rain, though city of New Orleans spokesman Ryan Berni said only minor street flooding and fallen trees were reported overnight.

He had no immediate reports of injuries or looting though he said one unoccupied structure had collapsed and there was a fire in a home caused by a candle. “Someone was reading by candlelight and the curtains caught fire,” he added.

Farther south in largely abandoned Plaquemines Parish, where Isaac made landfall Tuesday night, storm surge was piling up against levees between the Gulf of Mexico and the Mississippi River along the boot of Louisiana. A levee on the parish’s evacuated east bank had been overtopped.

Plaquemines emergency management spokesman Caitlin Campbell said an 18-mile stretch along the thinly populated east bank was being overtopped by surge. Sheriff’s deputies were going house-to-house getting residents who’d remained after an earlier evacuation to move to higher ground. Campbell said water had not entered any house and no injuries were reported. The area affected extended from Braithwaite to White Ditch. Campbell said despite the overtopping, only minor street flooding was reported.

Parish President Billy Nungesser said a portion of the roof of his home had blown off. He described wind-driven driven coming into his home as “like standing in a light socket with a fire hose turned on.”

Hundreds of thousands of people were without power across the state’s southern parishes, including more than 250,000 in New Orleans and its suburbs, power provider Entergy reported.

Though Isaac wasn’t packing Katrina’s punch, evacuations were mandatory in about a half-dozen parishes.

Coastal communities were largely abandoned after evacuation orders.

Houma, an oil patch community about 30 miles inland, was in darkness after power failed. The center of Isaac was expected to pass over the city as the storm slowly moved inland.

Officials in St. Bernard Parish, just east of New Orleans, reported flooding in coastal areas but that roads remained passable.

In New Orleans, large pumps designed to remove any floodwater from the low-lying level city on the Mississippi River were functioning as planned, Berni said. But he urged residents to remain vigilant and sheltered as long as the winds and rain bands were lashing New Orleans.

“We fully expect people to stay inside and not impede any efforts by our first responders,” Berni said.

Early Wednesday, police officers were patrolling and TV news trucks moved about streets where water ponded along the sides. The still-passable streets downtown didn’t appear to be seriously flooded though some wind-blown tree branches and signs littered the ground.

Buildings in the downtown also didn’t appear to have any significant damage.

At the International House Hotel, just outside the French Quarter, an early morning false alarm roused guests after windblown debris apparently shattered a window.

Michael DeBaets, 39, and his girlfriend Kelsey Dewis, 27, from Winnipeg, Canada, said they were a bit unnerved.

They were supposed to fly out of New Orleans on Wednesday after a vacation but the flight was canceled. It was deja-vu for the couple as they were trapped for two days in New York City last year when Irene, another hurricane, rolled up the Eastern Seaboard.

About 3 a.m. Wednesday, they were awakened by the sound of their hotel window shattering — possibly by flying debris.

It was a nerve-wracking experience.

“I just don’t know what to expect,” Dewis said. “Hurricanes are so foreign to us.”

She and her boyfriend joked that their next vacation probably won’t be anywhere near a coastline.

“Definitely inland,” she said. “Saskatchewan or something.”

In Terrebonne Parish, traffic signals swayed amid sheets of wind-driven rain as Isaac lurked nearby. Debris littered roadways.

Farther east in Plaquemines Parish, where Isaac made landfall at 6:45 p.m. CDT Tuesday, parish officials reported extensive damage. Isaac’s storm surge swelled the Mississippi River from its mouth upriver to New Orleans. In parts of Plaquemines, the river was lapping at the levee top.

Power outages were widespread and expected to grow as Isaac moved inland on Wednesday. An estimated 3,000 people were in shelters across Louisiana, state officials said.

In New Orleans, thousands of law enforcement officers and Louisiana National Guard troops were poised for possible rescue efforts. Roadways in the city’s eastern sector were reported flooded and trees were down.

Earlier in the day, floodgates were closed on area waterways to block Isaac’s storm surge, part of the flood protection system rebuilt with billions of dollars of federal aid after Hurricane Katrina struck seven years ago.

At a news conference Tuesday, just minutes after forecasters said Isaac hit land, New Orleans Mayor Mitch Landrieu said the city expected a lot of rain and wind.

“Now is the time to hunker down. Now is the time to be smart,” Landrieu told residents.

Isaac was moving toward the northwest and was expected to expose the city to its nastiest weather.

Power providers Entergy and CLECO began reporting outages and by late Tuesday more than 200,000 customers were without electricity across Louisiana. The number was expected to grow as the storm moved inland. The Baton Rouge area was hard-hit by Hurricane Gustav in 2008, with prolonged power outages.