Thursday, May 4, 2017

Lake Okeechobee and a sobering read: The Lloyd’s of London report

The Army Corps of Engineers has been putting a lot of resources and effort into making the Herbert Hoover Dike safer and more secure. (The dike is more accurately referred to as a dam now because it’s being used for water storage.) You can read about that here, an excerpt: 

     The corps inventoried all dams in the country after Hurricane Katrina in 2005. It found the Hoover Dike urgently needed some repairs to prevent a catastrophic breach of the dike.

The report by Lloyd’s of London* is one of the most alarming things you’ll ever read if you live in south Florida. Below is an excerpt from that report on the Herbert Hoover Dike (which technically no longer serves as a dike):

     And this brings us to the key concern; the dyke is no longer being used solely as a levee to protect the area from flooding when storms are in the vicinity but also to hold a permanent reserve of water. The lake is being used as a reservoir and therefore the dyke is now operating as a dam. [emphasis added]
     This means that water is pushing against the dyke nearly all of the time and that the risk does not come solely from a hurricane event. The dyke must act like a normal reservoir, i.e. be able to safely store floodwaters without overtopping.
     The dyke was built from un-compacted earth, made up of naturally porous materials such as peat, gravel, sand and shell and is therefore prone to leaks.
     Since the construction of the dyke, the land outside of the dyke has been eroding, particularly on the south side of the lake.
     The Herbert Hoover Dike, when built, was never intended to be used in this way and it has only recently been designated to be a dam. The flood criterion for dams is far more stringent than that which it has previously been subject to and also to which it is currently able to meet.

*Google search, “The Herbert Hoover Dike: A Discussion of the Vulnerability of Lake Okeechobee to Levee Failure, Cause, Effect and the Future” for the PDF.

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