Rising flood waters swamped this central US river city, forcing residents to flee their homes and officials to abandon city hall amid a wider crisis that has left 20 dead.
"We've been in a major flood fight for about 10 days now," Bret Voorhees, spokesman for the Iowa Homeland Security and Emergency Management, told AFP.
"Nine of our major rivers are at record or new record levels. We're designating it a 500-year flood."
The state capital Des Moines, population 200,000, urged residents living within the "500-year flood zone" to evacuate yesterday as the Des Moines River was expected to rise to near the top of the levee.
A total of 15 lives have been lost in Iowa and thousands were left homeless, Voorhees said, while 10 counties are under evacuation orders and 83 of the state's 99 counties have been declared disaster areas.
Two people were killed by floodwaters in Indiana and two delivery people drowned Sunday when their car fell off a washed out road into a flooded creek, the National Weather Service said.
Another person was killed Wednesday when a tornado ripped through the town of Chapman, Kansas.
The disaster began when a major tornado struck on May 25. It was followed by heavy rains, with more thunderstorms expected this weekend, and on Wednesday another twister touched ground in western Iowa, killing four boy scouts.
Serious flooding has hit the entire region, including parts of South Dakota, Minnesota, Wisconsin, Nebraska, Illinois, Indiana, Kansas, Oklahoma and Arkansas and was expected to continue through next week.
At least 53 locations in those states were expected to see "major flooding" in the next two days, the National Weather Service said.