IOWA CITY, Iowa — Heavier-than-expected rains and near-record high river levels for the Iowa River upstream in Marshalltown have spurred plans to increase the outflow rate at the Coralville Lake dam.
And that is expected to cause flooding and disruptions in the coming days.
Meanwhile, officials have proclaimed a state of emergency for Johnson County and are seeking a state disaster declaration in the wake of a punishing thunderstorm on Monday. The storm knocked out power for about 6,600 residents and closed roads due to flash flooding and fallen trees, including limbs falling on a pedestrian and an occupied car, and a power line falling on another occupied car.
Through Monday afternoon, officials thought the Iowa River could be contained in its banks, but the projections changed considerably on Tuesday.
“That extra three to five inches clearly changed the projections from yesterday’s numbers,” said Terrence Neuzil, Johnson County Emergency Management spokesman.
Neuzil said residents should brace for flooding similar to the early summer of 2013, when Dubuque Street was closed for about two weeks. In recent years, the area also has dealt with flooding in 2010 and 2008.
Neuzil said as the river level recedes from Monday’s rain, the outflow rate from the Coralville Lake will be increased to create additional capacity.
The outflow rate at the dam is being increased from 7,000 cubic feet of water per second to 10,000 cfs on Tuesday. It then gradually will be increased to 13,000 cfs by Thursday, and to 16,000 cfs after Thursday and until further notice, according to information from Johnson County Emergency Management.
The agency was briefed on Tuesday morning by Jim Stiman of the Army Corps of Engineers.
The water level increased 2.65 feet by midday Tuesday, up to 699.72 feet, and was expected to rise another two feet within 24 hours, according to data from the Corps of Engineers.
The biggest casualty for the area could be Dubuque Street, which remained partially closed on Tuesday due to Monday’s flash flooding.
One or more lanes of Dubuque Street flood when the reservoir outflow reaches 11,500 cfs. At 12,000 cfs, Dubuque Street is lost, said Dave Wilson, coordinator for Johnson County Emergency Management.
Based on the current projections, Dubuque Street will be closed by Thursday.
The current extended forecast, which calls for some sunny days and chances of rain other days, is a relief, said Rick Fosse, Iowa City’s public works director. But the threat of flooding will remain for weeks, he said.
Dubuque Street will remain closed for at least a week and a half — and possibly longer if there is additional significant rainfall, he said.
“Until the reservoir level gets back under 700, that’s when we develop a sense of comfort and relief,” he said.
Dubuque Street is a major route into and out of Iowa City and the University of Iowa campus and has on and off ramps to Interstate 80. When it closes — something that has occurred for 150 days in the past two decades because of Iowa River flooding — it affects traffic elsewhere in Iowa City and Coralville as drivers seek alternative routes.
Iowa City currently is in the design phase of a project to elevate Dubuque Street and the nearby Park Road bridge. Construction may start in 2016.
Rides, shelters and baseball diamonds at Lower City Park were closed on Tuesday due to flooding. It’s not clear when they’ll be reopened.
The city does not expect any flooding of homes based on the current forecast, Fosse said. The city is in the middle of building a levee on the west side of the Iowa River on the south side of town by two mobile home parks. It will install HESCO barriers there later Tuesday as a precautionary measure, Fosse said.
Coralville officials were not anticipating any street closures or the need to take other preventive measures based on the forecasts Tuesday, said Ellen Habel, assistant city administrator.
University of Iowa is installing HESCO barriers to protect the Mayflower Residence Hall, which is adjacent to the section of Dubuque Street that is expected to flood.
During Monday’s storm, four metal panels from a project to install a new scoreboard at Kinnick Stadium blew onto four cars in the parking lot below. Officials said the damage still is being assessed, but no one was injured.
While the area braces for flooding from the Iowa River, residents and city crews are still recovering from Monday’s storm. Several roads remain closed.
Johnson County Emergency Management asked Gov. Terry Branstad’s office to declare a state of disaster based on “severe damage to public and private property, disruption of utility service, and endangerment of health and safety of the citizens of Johnson County within the disaster area.”
Johnson County Board of Supervisors have declared a state of emergency, which allows the expenditure of emergency funds.
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