Some blame NOLA levees for rural floods

A air boat speeds past debris and a flooded home along Louisiana Hwy 23 amid receding flood waters from Hurricane Isaac, near Port Sulphur, La., in Plaquemines Parish on Monday, Sept. 3, 2012. / AP Photo

(AP) LAPLACE, La. - At the urging of residents who have long felt forgotten in the shadow of more densely populated New Orleans, the Army Corps of Engineers says it will look into whether the city's fortified defenses pushed floodwaters provoked by Hurricane Isaac into outlying areas.

However, the Corps has said it is unlikely scientific analysis will confirm that theory, suggested not only by locals, but by some of the state's most powerful politicians. Instead, weather experts say a unique set of circumstances about the storm — not the floodwalls surrounding the New Orleans metro area — had more to do with flooding neighborhoods that in recent years have never been under water because of storm surge.

Isaac was a large, slow-moving storm that wobbled across the state's coast for about two and a half days, pumping water into back bays and lakes and leaving thousands of residents under water outside the massive levee system protecting metropolitan New Orleans. It was blamed for seven deaths and damaged thousands of homes on the Gulf Coast.

The Corps' study was prompted by the suggestion that Isaac's surge bounced off the levees and floodgates built since Hurricane Katrina in 2005 and walloped communities outside the city's ramparts.

Blaming the Army Corps of Engineers is nothing new in southern Louisiana, a region that is both dependent on the Corps and by instinct distrustful of an agency that wields immense power in this world of harbors, wetlands, rivers and lakes, all of which fall under the agency's jurisdiction.

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The Corps was roundly criticized after Hurricane Katrina, which pushed in enough water to break through the levees that had surrounded New Orleans. Much of the city was left under water, and since then the government has spent millions rebuilding the system of floodwalls protecting the metro area.

Before that, the Corps was blamed for the unraveling of coastal marshes by erecting levees on the Mississippi River.

In towns including the bedroom community of LaPlace, people want answers. There, communities were under water even though they had never before flooded because of storm surge.

"It has a lot of us questioning," said Ed Powell, a 47-year-old airport emergency worker who's lived in LaPlace for 15 years and had never seen flooding on his street until Isaac hit.

On Friday, U.S. Sen. David Vitter asked the Corps to commission an independent study to determine if the new floodwalls, gates and higher levees around greater New Orleans caused water to stack up elsewhere.

115 Photos

Hurricane Isaac and its aftermath

The Corps is expected to complete its study within two months, said U.S. Sen. Mary Landrieu, D-La., who joined Vitter in calling for the study. The Corps said it was too early to say how much the study would cost. The agency said Corps researchers would conduct the study and that it will be peer-reviewed.

In a statement, the corps said it expects the study will find "minimal" changes in surge elevation because of its works around New Orleans. It based that assessment on previous modeling. The agency said it would not comment further until the scientific work is done.

Isaac came ashore as a Category 1 storm, but that classification is based on wind speed, not surge predictions. In the past, much stronger storms have produced much smaller surge levels. Isaac had a broad wind field — at times, more than 200 miles from its center — that made it capable of scooping up a lot of water, said James Franklin, the chief of hurricane operations at the National Hurricane Center in Miami.

Really strong hurricanes can sometimes produce small surge levels while weaker hurricanes — ones like Isaac — can kick up massive surge. For example, in 2004, Hurricane Charley hit Florida as a compact Category 4 storm and produced a surge of only about 7 feet. By comparison, Isaac created storm surge of more than 6 feet at Lake Pontchartrain, according to U.S. Geological Survey sensors. It reached about 12 feet near Braithwaite, a community flooded to its rooftops in Plaquemines Parish.

"It was like scooping up water with a broad shovel rather than a pencil point," he said, comparing Isaac to a more compact storm like Charley.

Furthermore, the storm's size, slow speed and the way it angled into the state "worked together to produce incredibly high surge," said Jamie Rhome, a surge specialist with the National Hurricane Center.

"The water piled up," he said.

Other scientists agreed it was unlikely New Orleans' fortified defenses caused flooding in neighboring communities. Instead, numerous factors combined to create ideal flooding conditions. For instance, the storm was virtually stationary for a time and dumped rain far longer than many other tropical systems.

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[varigdc10]

When I was still in high school I remember my chemistry teacher say " matter cannot be created or destroyed, it just changes physical state, as solid, liquid, or gaseous. So, as related to this matter of Isaac in louisiana when the Corps built up the leevies, it simply re-directed the flow of water around the protected area. It follows than that unless the water goes back to the ocean it will go into all low lying regions inland of the protected area. The Corps then has to calculate where in fact the water will be re-distrubited, unfortunately it may go into places where it never went before, as in this case. Had the Corps done a better job in calculating ( engineering ) where the water would go and directing the flow into benign regions this would not have happened, so I find the corps guilty of bungling this job, subject closed.

[parisdakar]

It's a shame but the handwriting is on the wall. New Orleans doesn't have a long term future. They need to come up with a 'sunset plan'. It's a waste to keep spending money on fighting the inevitable.

[tsigili]

If you are in coastal lowlands, and you get a hurricane, you are going to get flooded.

Those fools need to ask why people built where they built!

[Matt_in_MN]

Fool me once...

[karek40]

Isn't asking the people who designed the levees to investigate whether they caused the flooding kind of like asking the fox to watch the hen house? Obvious study answer after spending millions of our tax dollars, "The levees significantly reduced the lose of life in the more densley populated areas and only marginally contributed to the flooding in the outline rural areas". Since the results of the study are now published have them send all moneys required to conduct the study to karek40. LOL

[ahrats]

The ACOE think they are GOD. They have no clue what they are doing when the weather does no do what they expect. The Flooding was caused by 2 1/2 days of steady rain and levies that are there are to keep water out. Once inside the levie there is no drainage and the natural state of the surrounding land, being lower than the level of the Gulf of Mexico can not drain. Give it a few weeks and the water will evaporate naturally unless another storm comes. A pump will not do since there is no place to pump the water except maybe to Texas or Oklahoma where they should could use it for their drought conditions.

[maiingan]

The Mississippi Delta extends much farther upstream than La Place. A delta is a depositional landform. All of it is deposited by water. Most of it is deposited by the river. This area, and well inland, are also at high, reliable risk from hurricanes with the rains and storm surges. Storm surge might bring in a little sediment, but it's mostly an erosional force. Once people started to build artificial levees, along with upstream dams, the natural supply of sediment from the river was greatly diminished, with the result that the erosive forces of sea and heavy rain get the upper hand. Also, when you block natural river flooding, the dried-out land sinks more from loss of water. The people complaining the most about this latest flooding surely are the ones with the least science education in this field. Rebuilding there is a losing battle.

[taxed01]

How many more BILLIONS of taxpayer money is going to be spent so people in that area can live in flood zones?