Flooding

"Whenever you have development, you are going to increase the runoff, increase how much the rivers and streams have to carry," says civil engineer W. Gene Corley, a senior vice president at CTLGroup, an engineering firm that constructs levees. "The other side of that is that if you don't have development, you don't have housing for people or business or manufacturing."

In addition, by paving over previously open space—or farming previously reserved lands—communities in these watersheds contribute to record high waters through increased runoff.

This extra runoff is why waters in Cedar Rapids, Iowa, for example, rose to a record 30-plus feet (over nine meters). "The amount of development that has happened in communities up and down the river way creates less opportunity for water to be absorbed back into the earth as opposed to just running off," notes structural engineer Jeffrey Garrett, president and CEO of CTLGroup. "Suddenly, you've got a lot more water that has to flow between the levees."

So, restrict development, then?