For historic city, a fateful forecast

Disaster modeling indicates storm such as Katrina could flood low-lying city, killing tens of thousands

Hurricane Katrina

August 29, 2005|By Frank D. Roylance | Frank D. Roylance,SUN STAFF

With Hurricane Katrina bearing down on the Gulf Coast yesterday with the threat of a 25-foot storm surge and 15 inches of rain, the city of New Orleans could hardly be in greater natural peril.

The city, founded by the French in 1718 on what seemed relatively safe high ground beside the Mississippi River, is now situated 6 to 8 feet below sea level, in a saucer of silt, sand and clay.

The river and Gulf of Mexico are held back by a system of levees and storm gates. And every inch of water that seeps in, or rain that falls, must be removed by one of the world's largest pumping systems.

That system could undergo its biggest test today as New Orleans faces one of the most powerful storms ever to threaten the United States.

Disaster modeling suggests that the consequences of a Category 5 storm such as Hurricane Katrina could be dire -- pumps disabled by flooding, 20 feet of water in the streets and tens of thousands dead. Experts have warned that the city could be left paralyzed for months by water, debris, demolished buildings, and a hazardous soup filled with sewage, petrochemicals, alligators and fire ants.

"Everyone keeps saying, `This is the big one. This is the one that could tell us how leaky that hurricane protection system is,'" said University of New Orleans geologist Shea Penland. "I hope not. I hope the risk won't be counted in body bags."

Penland sent his family to Shreveport, about 280 miles away. Most have left New Orleans, but he is staying. He and his golden retriever are holed up with a generator in his century-old Victorian home, built on one of the city's levies.

"I'm in the business, and this one's coming right to me," said Penland, director of the university's Ponchartrain Institute for Environmental Science. A longtime student of hurricanes and their effects, Penland has often warned that the city is ill-prepared for a storm of Katrina's power.

"I had planned to leave," he said in a telephone interview. Then he told his wife he'd changed his mind. "I said to her, `I want to stay.' She said, `You're nuts. Call me every hour and let me know how you're doing.'"

Hundreds of thousands of New Orleans' 462,000 residents had left by yesterday afternoon.

"This place is a ghost town," Penland said.

Category 5 storms

It should be. Hurricane Katrina was a fearsome Category 5 storm on the Saffir-Simpson scale, capable of catastrophic damage.

Only three other Category 5 storms have made landfall in the United States since record-keeping began: An unnamed storm hit the Florida Keys on Labor Day in 1935, killing 409 people. Hurricane Camille struck the Mississippi coast in 1969, killing 259. And Andrew ravaged South Florida in 1992, killing 15 and leaving $26.5 billion in losses -- the costliest hurricane on record.

Category 5 storms have sustained winds in excess of 155 mph, enough to cause complete roof failures and some building failures. Mobile homes are demolished. Buildings within 500 yards of the shore and 15 feet of sea level suffer major damage to lower floors.

Katrina was intensifying, with peak sustained winds yesterday over 160 mph.

"This looks like the worst I've ever seen professionally for New Orleans," Penland said.

Atmospheric pressure in the hurricane's eye was 902 millibars (26.64 inches of mercury), the second-lowest barometric reading ever recorded in the United States after the Labor Day storm's 892 millibars.

A vulnerable city

New Orleans' vulnerability stems from several factors. First, the soil the city was built on has been settling for 300 years, and drainage for development has made it sink faster. It's still sinking by a third of an inch per year, and sea level is rising. Ships passing along the levee float yards above streets in the French Quarter.

Flood-control projects upstream have cut the flow of sediment, leaving the Mississippi Delta south of the city without natural replenishment.

"That natural buffer of marshes and barrier islands has diminished by 40 to 50 percent since the middle of the 20th century," Penland said. "Anyone who lives down there will tell you that [what were once considered] small storms have become big storms in the last several decades."

The city responded after 1910 by building a system of levees, floodgates, 22 pumping stations and 180 miles of open and buried canals. It is still being enhanced and enlarged, at a cost of hundreds of millions of dollars and with a goal of protecting the city from Category 3 storms.

New Orleans was pumping water yesterday from its drainage canals into Lake Ponchartrain to the north, making room for storm water. Heavy steel floodgates in the levees were closed and sandbagged, sealing off the roads that pass through them.

"If the rain rate exceeds 4 inches per hour, the pumps can't pump it out fast enough," Penland said. "The area inside the levy starts filling with rainwater." Katrina was expected to dump 5 to 10 inches of rain in New Orleans, with 15 inches in places.

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