To CRCL Board members and interested folk.

Nothing's Easy for New Orleans Flood Control

Science section / The New York Times / Tuesday, April 30, 2002

By JON NORDHEIMER

NEW ORLEANS - Caught between the Mississippi and the long

shoreline of Lake Pontchartrain, this low-lying city has

long depended on levees and luck.

Now engineers say those are not enough to protect New

Orleans, much of it below sea level, from a devastating

flood that could threaten it if a storm surge from a

powerful hurricane out of the Gulf of Mexico propelled a

wall of water into the lake and the city.

That event could place vast sections under 20 feet or more

of water, engineers and scientists say, with worst-case

computer predictions showing death tolls in the tens of

thousands with many more people trapped by high water that

has no natural drainage outlets.

"There's no way to minimize the amount of devastation that

could take place under such circumstances," warned Walter

S. Maestri, director of emergency management of Jefferson

Parish, a suburban region with 455,000 residents on the

city's western and southern sides.

Perhaps the surest protection is building up the coastal

marshes that lie between New Orleans and the sea and that

have been eroding at high rates. But restoration will

require time, a huge effort and prohibitive sums of money,

perhaps $14 billion, according to a study by a panel from

federal and state agencies, universities and business.

Engineers are considering other ways to protect the heart

of the city and provide an island of refuge in the French

Quarter and government centers. Though such approaches are

less expensive, they come with their own problems. One plan

involves walling off an area to keep out water. But where

would the wall be built and who would benefit from it?

Many residents give little thought to such matters,

counting on the knowledge that New Orleans has escaped

hurricane disaster in the past.

The most nervous people are those paid to worry about such

things, like Dr. Joseph N. Suhayda, director of the

Louisiana Water Resources Research Institute at Louisiana

State University. Like other coastal researchers, he has

been using the latest geological and meteorological data to

refine computer models of how different storms would damage

the city.

On a bright spring day with fair skies and no trace of the

sultry air that will dominate the weather in the months

ahead, Dr. Suhayda and a few colleagues drove city streets

1,000 yards from levees that hold back Lake Pontchartrain.

At New York Avenue, near the lakefront campus of the

University of New Orleans, the car stopped, and the

engineer walked over and unfolded a wood measuring stick to

its 25-foot length. He planted one end on the pavement and

raised it until it was vertical. The other end poked into

the sky well above a corner light pole, but it was still

well beneath the level of a concrete wall that rose on top

of a grassy slope 100 feet away.

"Behind that," Dr. Suhayda said, indicating the wall, "is a

canal that runs into Lake Pontchartrain. Its surface is

roughly about the same as the lake's surface."

In a hypothetical situation projected by his computers, Dr.

Suhayda continued, a slow-moving Category 4 hurricane, with

winds up to 155 miles an hour, or a Category 5 hurricane

with even stronger winds could leave water 30 feet deep on

this neighborhood street, which is more than five feet

below sea level. Though Category 5 hurricanes are very

rare, Camille in 1969 devastated Pass Christian, Miss.,

just 50 miles east of New Orleans, and killed scores of

residents with winds that exceeded 200 miles an hour and a

35-foot storm surge.

In most areas vulnerable to hurricanes, the water would

drain away quickly. That is not the case here.

So city planners and engineers continue to work on ways to

improve an evacuation plan for the 1.3 million residents in

the metropolitan region and to soften a storm's blow. Most

long-term projects intended to blunt a hurricane involve

slowing the loss of marshlands. One method calls for

additional control gates to let the Mississippi pour

sediment-rich water into surrounding lands, a process that

would eventually raise or at least maintain their

elevation.

Other proposals are to rebuild eroded offshore barrier

islands, erect a wall of levees across much of the lower

delta, plug the dredged containership channel that gives

the Gulf of Mexico waters easy access to the vulnerable

eastern shore of Lake Pontchartrain and help defend that

shore with higher flood gates.

Perhaps the most unconventional is the "community haven"

concept advanced by Dr. Suhayda and others in the belief

that radical remedies may be necessary to soften a knockout

punch by nature. More theory than an organized campaign, it

envisions a two-story-high wall with flood gates at crucial

intersections to seal off the southern part of the city

from a bend in the river at the French Quarter to another

one eight miles west.

If the rest of the city flooded, Dr. Suhayda said, the

"island" between the wall and the river's levees could

become a refuge for thousands of residents fleeing their

homes, as well as preserving the cultural and government

center.

But obtaining the money on the scale needed is far tougher

than devising plans, especially if some skeptics dismiss

the worst-case predictions as scare tactics to help finance

university research or for further environmental intrusions

on the coast.

Researchers, though, say they are not making up the city's

potential peril, which arises from geology and history. As

tight as a pimento in an olive, most of New Orleans is

stuffed between the Mississippi and the lake, and it is

settling as fast as the rest of the delta or faster, said

Dr. Roy Dokka, a geologist at Louisiana State.

Although much agonizing has gone into problems of the

river, and its metaphoric temperaments have become part of

songs and folklore, it is the 300-square-mile lake that

troubles him, Dr. Dokka said.

As New Orleans grew as a seaport, petrochemical hub,

tourist destination and cultural phenomenon, neighboring

marshes were drained and the levee system expanded to keep

the water out of new suburbs and industrial parks,

hastening the drying that led to sinking, and making a bad

situation even worse.

A computerized cross-section of the city's topography

recently created by L.S.U. scientists and engineers shows a

shallow bowl-like profile. On the southern edge along the

river, the rim rises about five feet above sea level for

most of the French Quarter, a half-mile-wide sloping plain

created by the river's natural earthen banks. A flood wall

built by the Army Corps of Engineers to hold back a

cresting river - which on normal days moves more than

300,000 cubic feet of water a second past the city at an

average depth of 90 feet - raised the levee to a uniform

height of 25 feet above sea level, or 10 feet above the

average annual high water surface level of the river, when

water can rush by at the rate of one million cubic feet of

water, or more, a second.

Most of the city north of the French Quarter was reclaimed

from a boggy morass. The lowest sections - residential

areas and shops that sit on drained marshland at 5 to 10

feet below sea level - form a wide band near the lake's

southern shore.

New Orleans International Airport to the west and

industrial complexes and residential areas to the east are

at sea level or below it.

Spider webs of city canals and wide ditches that measure

185 miles in length feed 22 pumping stations that lift

water to a height where it can flow into the lake, over

levees built more than a half-century ago that stand 15 to

17 feet above sea level.

Water cascading over the levee wall or flooding from

swollen marshes at the lake's eastern and western ends is

just one part of the nightmare, the experts say. Draining

the city after the storm moves away may take weeks, they

point out. The city would be trapped inside the levees,

steeped in a worsening "witches' brew" of pollutants like

sewage, landfill waste, chemicals and the bodies of drowned

humans and animals.

Bourbon Street could remain under 10 feet of water, with

water swirling above two-story houses in neighborhoods

closer to the lake.

Dr. Ivor van Heerden, deputy director of the L.S.U.

Hurricane Center, said that in a worst-case situation with

incomplete evacuation "we could have up to 45,000 killed

and 400,000 trapped on roofs, with 700,000 evacuees who

would now be homeless."

Dr. van Heerden said it would take at least nine weeks to

pump the city dry.

Pumping stations, which sometimes fail in heavy seasonal

downpours in a city that receives nearly five feet of rain

a year, would be inoperative under those conditions for

days if not weeks, Dr. van Heerden said. The chemical stew

that would be pumped into the lake and surrounding marshes

would be an environmental disaster by itself, he added. He

said that the cost in human misery might be incalculable

but that the bills for insured damages, public works

repairs and replacements and the economic effects might

total $50 billion.

Despite the specter of such losses, it has been difficult

to find enough money to build up the protective marshlands,

said Jack C. Caldwell, head of the state's Natural

Resources Department. Washington has been disinclined to

earmark billions to protect the marshland and has resisted

appeals from Baton Rouge to share revenues from offshore

oil production with the state for that purpose, Mr.

Caldwell said.

In the meantime, residents take their chances every

hurricane season, which starts on June 1. According to his

computer models, Dr. Suhayda said, the odds that the city

will be hit by a cataclysmic storm in any given year are

less than 1 in 100.

The American Red Cross is taking the threat seriously. It

has declared it no longer will provide hurricane shelters

in the New Orleans area, saying that placing staff there in

a killer storm will represent too much risk for its

employees, volunteers and the general public.

-end-

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