Looking Back at a Big Flood

The Des Moines Register looks back at the massive flooding on the Iowa River and the Cedar River in 2008:

 First comes the melting of the third-heaviest snowpack in Iowa history. Then intense rainstorms pummel the state. Several northern Iowa cities report 10 to 14 inches of rain over 16 days. Rivers rise rapidly in early June, and Iowans turn to a dreaded but familiar pastime — sandbagging. Des Moines, Creston and Ottumwa all see rivers rise out of their banks. In eastern Iowa especially, the floods come with rare force. In the Cedar and Iowa river basins, torrents of water blast beyond so-called 500-year flood plains, destroying hundreds of homes and businesses, tearing apart bridges and roads, and forever changing the landscape and Iowans' fortunes.

Here's a map from Cedar Rapids:

The 500 year flood plain, as calculated by FEMA, represents a very large flood.  Unfortunately, between a small data set and climate change, we're probably going to have to recalibrate the probabilities of such events.