A new model of the Iowa River reveals that a cofferdam did not cause as much flooding last summer as many originally thought.
Some residents of the upstream Idyllwild neighborhood, located northwest of Terrell Mill Park, blamed elevated water levels on the cofferdam, a temporary structure that acts as a barrier for a construction site on the riverbed.
But the new model showed the UI cofferdam raised water upstream near the Park Road bridge by only 4 inches during the June 2008 flood, which is less than officials originally thought.
The river model, unveiled April 10 by UI officials, is a computer program that accurately describes the shapes of the land, river channel, and structures such as buildings, bridges, and dams. It is capable of determining how high water levels would get at any given location for a certain flow rate, said psychology Professor Gregg Oden, a co-head of the UI Flood Mitigation Task Force.
This can predict whether a location would be threatened by any future flooding at a specific flow rate, said Larry Weber, a UI professor of hydroscience and engineering.
The predictive tool can foresee flooding for a 12-mile stretch along the Iowa River, stretching from the Coralville Dam to southern Iowa City.
The UI is working together with Coralville, Iowa City, and Johnson County, making the model available to all the groups for use in future flood planning.
“I appreciate the fact that we’re doing a unified project,” said Iowa City Mayor Regenia Bailey.
Since the UI unveiled the program, Coralville officials have said they plan to use the model to test a proposal to raise part of the CRANDIC railroad tracks along the Iowa River, said Coralville city engineer Dan Holderness.
“There’s a high level of cooperation happening,” he said. “We don’t want to formulate anything that will negatively impact our neighbors.”
The river model was developed under the direction of consultants from Ayres Associates, an engineering firm in Ft. Collins, Colo. Members of the Flood Mitigation Task Force, a committee formed to advise the university on future campus flooding, meets regularly with the consultants to discuss work with the model.