Saturday, January 14, 2012

Climate change miscalculation endangers Des Moines Riverwalk

David Elbert in the Des Moines Register explains a terrible error that throws a costly piece of new infrastructure into jeopardy. Why, yes, the Army Corps of Engineers was involved, why do you ask?: A little more than a year ago, Des Moines City Manager Rick Clark received a piece of shockingly bad news that is likely to take years and nearly $40 million to fix. The gist of the news was that federal officials had recalculated a worst-case flood on the Des Moines River, and the new numbers showed water in downtown Des Moines was likely to rise nearly two feet higher than previously projected.

The new flood estimates from the U.S. Army Corps of Engineers arrived in December 2010, just as the city and Principal Financial Group were ramping up to complete the final phases of the downtown Principal Riverwalk.

The new calculations meant that the flood specifications used in the design of the $70 million riverwalk were no longer valid. It meant that the riverwalk, and several million dollars’ worth of flood protection associated with it, was designed and built based on a worst-case flood that was nearly two feet lower than what the new numbers indicated.

...The new information created a virtual train wreck. The city and Principal had to figure out what to do. The riverwalk was more than 90 percent complete, but it was already several years behind schedule. Should they stop everything until new, higher flood walls could be designed and built? Or should they go ahead and finish the riverwalk while they figured out a Plan B?

There really wasn’t much choice, Clark said. The riverwalk project had to move forward, and it will. Paving of most of the walkway is expected to be completed late this year or early in 2013, and once it is, the riverwalk will formally open. But the work will now take place against a backdrop of uncertainty...

The Des Moines skyline, shot by Des Moines Guy, Wikimedia Commons, under the Creative Commons Attribution-Share Alike 3.0 Unported license

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