New UI study finds flood risk rising in northern states including Iowa

A new University of Iowa study delivers a warning for areas of Iowa still recovering from fall flooding.

Iowa and other parts of the northern United States have seen a measurable increase in the number of flood events according to the study published online last Saturday at Geophysical Research Letters. However, states in the southern part of the country may be seeing fewer floods based on a statistical study of the last 30 years.

And the study, performed by researchers at the university’s Hydroscience and Engineering program, found one reason for the change was a shift in rainfall patterns over that period of time.

Gabriele Villarina, associate professor and co-author of the study, said researchers focused on more frequent minor and moderate flood events rather than the much rarer major flood events like the one that hit Cedar Rapids last fall.

“There were some interesting results. We found the US as a whole wasn’t going in the same direction,” Villarini said.

Villarina said researchers took 30 years’ worth of data from about 2,000 stream and river gauges to find where floods had occurred since 1985. That was matched with rainfall totals and NASA satellite images of water stored in the ground to find the connection. The research showed a definite shift in rainfall patterns with northern states, including Iowa, getting more frequent precipitation and southern states getting less with the chances of flooding dropping a bit.

He said what researchers can’t explain yet is why rainfall patterns are changing. Is it due to human activity or simply a natural change in climate patterns?

“This is something we are actually exploring an hopefully within the next few months we’ll have more definitive answers to this question,” Villarina said.

Villarina said the study just published took about six to eight months to complete.