Cedar Rapids Gazette: Computer Model Helps Iowa Cities, Public Prepare for Flood

Wednesday, May 29, 2013

In 2008, area officials relied on what were essentially back-of-the-envelope calculations to predict where floodwaters could reach.

This year, with flooding again a concern, they have a new tool that is more precise and as simple to use as getting on the Internet.

Since the historic 2008 floods, the Iowa Flood Center at the University of Iowa has developed a web-based model that creates flood inundation maps based on river conditions in the Iowa City area, Cedar Rapids and eight other towns in Iowa, with a few more coming soon.

It allows people to map out what-if scenarios at various river heights and flows.

That’s a tool local communities have used this week as wet weather has led to predictions Coralville Lake could reach its emergency spillway, threatening downstream communities with potentially significant flooding.

Coralville has consulted the model to help develop plans for protecting the community should flooding turn serious. It also asked the Iowa Flood Center for a separate calculation considering different flows for Clear Creek, which meets the Iowa River near First Avenue and Highway 6.

Should flooding occur this year, the city expects to have a much better idea where water will go than it did in 2008.

“That’s really the advantage,  to give us a heads up and give us plenty of time to prepare,” City Administrator Kelly Hayworth said. “And it tells us where to start and where to prioritize.”

In 2008, as record-setting floods wreaked havoc on the state, local government officials were asking researchers at the UI’s IIHR – Hydroscience & Engineering (the Iowa Flood Center was created after the flood) to calculate where the water would reach.

The problem was it takes several weeks to build a proper model, plus the river forecasts were constantly changing, said Larry Weber, director of IIHR –Hydroscience & Engineering, one of the nation’s premier hydraulics laboratories.

Now, the flood center has validated flood maps at 6-inch increments based off data obtained from river and stream gauges. They take into account landscape and many of the flood-protection projects communities completed following the 2008 flood, Weber said.

Instead of those rough calculations in 2008, Weber and his colleagues now tell people with specific questions to go to the website for detailed, real-time answers.

The model is easy to use and available to anyone with Internet access. Looking at the Iowa City and Coralville map, one just has to click on a controller and slide it to the right to increase the height and discharge on the Iowa River, and the water expands accordingly on a Google Map.

“It will improve public safety and hopefully protect property as well,” Weber said. “We all have heard of the stories of, ‘We just didn’t think it could get this far.’”

“Now we have all these visual tools to be able to show people that for this flow, this is the extent and you need to prepare.”

Rick Fosse, Iowa City’s public works director, said Iowa City also is using the model this week to develop flood-protection plans. It partnered with the flood center and the National Weather Service on the project, spending about $9,000, he said.

“Which was a bargain considering what we get out of it,” he said.

Cedar Rapids Public Works Director David Elgin said the city already had a comparable application for its own internal use, but the Iowa Flood Center and similar National Weather Service maps are valuable for homeowners, businesses and industries near the river.

“It’s a very convenient tool for people to use and it does save time,” he said.