Two 500 year floods on Mississippi in 15 years?

I’m glad I’m not the only person that wonders why the media keeps referring to the current flooding in Iowa and along the Mississippi River a “500 year” flood. But, when you have a top General in the U.S. Army of Corps of Engineers, in an interview on the Today Show today call it that, I guess one can understand. 

But, this label has become obsolete. This is exactly what the authorities called the 1993 flood on the Mississippi - the 500 year flood. Now, 15 years later, we have another flood that seems to be exceeding the previous 500 year flood. In fact, in many places it is exceeding the 1993 flood.

"How possible is it that twice in just the last 15 years we've had two 500-year floods? ... People have been misled into feeling confident that they can live in flood plains," Criss said. (a professor of earth and planetary sciences at Washington University in St. Louis)  http://cosmiclog.msnbc.msn.com/archive/2008/06/18/1151113.aspx

"Anyone who has been around these parts awhile has stopped talking in terms of a '100-year flood' or a '500-year flood.' We know better. Floods like this don't happen every year. But we also haven't had any centuries-long breaks from severe flooding." http://www.thonline.com/article.cfm?id=205846 Dubuque Telegraph Herald

The old assumptions don’t count anymore. The towns along the Ohio better start putting tape measure to their flood walls. But it’s more than that really. It’s the entire management, or mismanagement of the environment for many decades which is leading to events like this. And, I am pretty sure that we will see more of them before we see less of them.

Bush is over in England sipping tea with the queen while the people in the midwest river valleys are struggling with untold disaster. This just proves that Bush didn't learn a thing from Katrina. He's still as detached from reality as ever. Today, after the flood waters have receded from Cedar Rapids and other Iowa Cities and towns, he's going to do a fly over. He should have been there shoveling sandbags. He'll probably do a short stint as a photo op for the nightly news. But once again, way too little, way too late.