<tt> A pretty good read, and probably one of many, clearly indicating that for a long, long time it's been known that a hurricane hitting New Orleans has been a disaster just waiting to happen.
</tt>excerpt from http://www.pubs.asce.org/ceonline/ceonline03/0603feat.html
"If a storm of category 4 or 5 were to hit New Orleans before the city was
adequately prepared, what toll would it exact?
In the 1980s Joseph Suhayda, then a coastal oceanographer in the civil
engineering department at Louisiana State University (LSU), began to seek an
answer to this question by simulating storms with a modified version of a
hurricane model used by the Federal Emergency Management Agency (FEMA).
Suhayda first began modeling the storms to help parishes in southeastern
Louisiana determine appropriate flood elevations for FEMA's National Flood
Insurance Program. As his modeling capabilities improved, he began to more
closely investigate the level of protection provided by the levees
encircling New Orleans.
Suhayda's model contains a geographic information system overlay that
divides a fairly large boundary, from Alabama to Texas, into 0.6 mi (1 km)
grids containing information about ground elevations, land masses, and
waterways. The FEMA hurricane model does not draw on the same processing
power as AdCirc and in general produces more liberal projections of flooding
from storm surges. But by solving numerical equations representing a storm's
pressure, wind forces, and forward velocity, Suhayda was able to use the
model to predict the storm surge associated with an actual hurricane dozens
of hours before it hit land. By subtracting the elevations on a
topographical map of coastal Louisiana from those surge values, he was able
to approximate the flood risk of a given storm.
In the 1990s, Suhayda began modeling category 4 and 5 storms hitting New
Orleans from a variety of directions. His results were frightening enough
that he shared them with emergency preparedness officials throughout
Louisiana. If such a severe storm were to hit the city from the southwest,
for instance, Suhayda's data indicate that the water level of Lake
Pontchartrain would rise by as much as 12 ft (3.7 m). As the storm's
counterclockwise winds battered the levees on the northern shore of the
city, the water would easily top the embankments and fill the streets to a
depth of 25 ft (7.6 m) or more.
Suhayda's model is not the only one that describes such a catastrophe. A
model called SLOSH (Sea, Lake, and Overland Surges from Hurricanes), which
is used by the National Weather Service and local agencies concerned with
emergency preparedness, portrays an equally grim outcome should a storm of
category 5 hit New Orleans. The SLOSH model does not contain nearly as many
computational nodes as does AdCirc, it does not use a finite-element grid to
increase the resolution of the nodes on shore, and its boundary is much
smaller. Even so, its results are disheartening.
"Suppose it's wrong," says Combe, the Corps modeler. "Suppose twenty-five
feet is only fifteen feet. Fifteen feet still floods the whole city up to
the height of the levees."
Experts say a flood of this magnitude would probably shut down the city's
power plants and water and sewage treatment plants and might even take out
its drainage system. The workhorse pumps would be clogged with debris, and
the levees would suddenly be working to keep water in the city. Survivors of
the storm-humans and animals alike-would be sharing space on the crests of
levees until the Corps could dynamite holes in the structures to drain the
area. In such a scenario, the American Red Cross estimates that between
25,000 and 100,000 people would die."
That prospect-and the amount of time it would take the Corps to construct
adequate levee protection against a storm of category 4-have inspired
Suhayda to push for what he calls a community haven project. His idea is for
the city to construct a 30 ft (9 m) tall wall equipped with floodgates
through the center of town to protect the heart of New Orleans and such
culturally important areas as the French Quarter. That portion of the city
lies between two bends in the Mississippi River and is therefore already
protected by adequate levees on three sides. With its gates closed, the wall
would complete a waterproof ring around the area.
Suhayda says the wall would be cheaper and faster to build than the larger
projects under consideration by the Corps. It could be constructed along an
existing right-of-way and act as a sound wall most of time. "We're going to
build sound barriers along most of these roads anyway," Suhayda says. "So
for a small added cost, go ahead and make them capable of withstanding wind
loads and hydrostatic heads."
The Corps would not necessarily be involved in the construction of such a
wall because the latter would be land based. Even so, Naomi is adamantly
opposed to the idea. "How do you protect people from
two-hundred-mile-per-hour winds?" he asks. "Where do they go? What buildings
are designed to withstand that? Where do they get their power and their
food, and where do they rest their heads at night? Just keeping the water
out isn't enough. You don't want to give people a false sense of security by
saying that this is a refuge unless you have a place for them to go."
For the most part, New Orleans does not have places for people to go. The
American Red Cross no longer provides emergency shelters in the city because
its officials cannot guarantee the structural integrity of the locations.
There simply are not enough buildings in the area that could withstand the
forces of a category 4 or 5 storm.
During the past 10 years Marc Levitan, a wind and structural engineer and
the director of LSU's Hurricane Center, has been involved in hundreds of
building investigations throughout New Orleans to determine if certain
structures could be used as so-called refuges of last resort. "With the vast
majority of them, if you really do an analysis, you really wouldn't want to
use them," he says. "They all have some sort of deficiency."
Most people would not wish to remain in the city if a category 4 or 5 storm
were in prospect, but evacuating could be difficult. Experts say close to
400,000 people could be stranded in the city. There are an estimated 100,000
people without easy access to automobiles, and those who can drive may not
be able to do so. During Hurricane Andrew, interstates throughout the South
were brought to a standstill because simultaneous evacuations were taking
place in several states. The only major planning improvement since then has
been the decision to keep traffic away from the coast on both sides of
evacuation routes.
Complicating the difficulty in New Orleans is the fact that each of the
city's three major evacuation routes is over or near water. Suhayda's model
indicates that during a storm of category 5 Interstate 10, which is
constructed on piers for a distance of almost 20 mi (32 km) west of the
city, could be covered by more than 5 ft (1.5 m) of water."
