Additionally though, Cedar Falls doesn't have nearly a million people to evacuate and shelter.
Neither did Louisiana. Remember, most of the people in New Orleans evacuated ahead of Katrina.
1. It's not below sea level, so it will drain. That's a big factor.
The level of flooding is actually quite a bit higher in Iowa, a dozen feet or more beyond what New Orleans saw, as bad as the worst areas in Alabama or Mississippi during Katrina. The fact that it may drain away more quickly only matters in terms of property damage if you can't hold your breath long enough...
Iowa will be fine. They will need a lot of disaster assistance but their rural/farmer heritage will leave them well equipped to get to work and solve problems once the immediate flooding is over.