U.S. Water News Online
NEW ORLEANS -- The U.S. Army Corps of Engineers has decided
to proceed with proposed floodgates as a way to prevent storm surge
from building up in three of the city's major drainage canals, two of
which breached during Hurricane Katrina.
"We just don't have the confidence in the canal levees at this
point," Corps spokesman Jim Taylor said.
Normally, the 17th Street, Orleans and London Avenue canals drain
rainwater pumped from New Orleans streets into Lake Pontchartrain.
But during Katrina, storm surge pushed from the lake into the canals,
ultimately causing levees along the 17th Street and London Avenue
canals to break open from the unusual pressure. The result was
flooding across western and central parts of the city, much of it
The new floodgates will remain open to allow rainwater to drain
out of the canals unless a major storm begins to reverse the flow of
water from the lake into the canals. In that case, the gates would
close to prevent water from coming into the canals while temporary
pumps would continue to move rainwater out.
"The level of protection is greater if you stop the surge at the
lake," Taylor said.
That was what the Corps wanted to do long ago, but the city's
sewerage and water board, which is in charge of draining the city,
fought that proposal, fearful the gates would interfere with the
drainage of rain water.
Instead, a compromise plan called for building up the canal levees
and reinforcing them with concrete floodwalls anchored by steel sheet
pilings driven into the ground. Since the water from Katrina's storm
surge never ran over the top of the 17th Street and London Avenue
canal walls, those levees should have held, many civil engineers
studying the damaged flood control system have said.
The breaches have raised questions as to whether the canal levees
were weakened by design flaws that could continue to leave them
vulnerable in future large storms. Many engineers studying the system
see the best long-term solution as building new, permanent pumping
stations at the mouths of the canals. That would allow drainage
pumping to continue at full capacity while the gates were closed. The
Corps must first get authorization from Congress to pursue such a
In the meantime, if heavy rain hits while the canal gates are
closed, some rainwater flooding could occur in the city, but that
would be preferable to the catastrophic flooding from Lake
Pontchartrain, Taylor said.
"If lake is high and it's raining hard, there's likely going to be
some interior flooding, maybe some homes flooding," Taylor said.
"We're analyzing that now to see what areas would be flooded based on
various scenarios ... and we'll be warning people to get out of the
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