Sunday, September 04, 2005

Patching Levees

The flooding of New Orleans brings up the question of how one can quickly patch a flooded canal.

The primary material used for patching levees is the sand bag. This really is an ideal material. You fill the bags with dirt then toss them into the breach.

The only problem with sand bags is that they require a large amount of sand near the breach.

This alert shows a picture of a helicopter moving filled sand bags to a levee breach. To get fill material apparently engineers are grinding up roads. I imagine that this is an incredibly expensive process. I understand the early efforts to patch the levees with helicopters failed because they couldn’t get the material to the canal fast enough.

The challenge in creating patches is getting fill material into the bags.

During levee breaches, the one material you have in excess is water. It would be interesting to design a levee patch with plastic tubes. You would fill the tubes with water and sink them in the breach. The tubes would have to be made with a plastic of an enormous tensile strength. After the plastic patch is in place, you can then set in a real repair...deflating the bags as you go.

Of course, the ultimate levee patching might simply be a portable conveyor system and designated areas with fill material.

Using helicopters to ferry sand bags is expensive and would not be fast enough to patch a growing breach.

Apparently the breached levees with engineered with an expected life time of 300 years. We seem to have proven that even overengineered levees can and will fail. The New Orleans flood shows that we need better patching technologies in place.

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