Flooding worries rise in Johnson County

Local officials are preparing for serious flooding south of Coralville Lake, but the forecast, while concerning, is not all gloom and doom just yet.

Computer models indicate Coralville Lake, a man-made reservoir meant to control flooding downstream along the Iowa River, can handle the heavy rain expected next week.

Still, Dave Wilson, Johnson County's emergency management coordinator, said Thursday he could not rule out something similar to what happened in 1993 occurring this year. Despite the recent sunshine, last month was the wettest June on record in Iowa.

“No, I would say we're not out of the woods yet,” Wilson told the county's supervisors during a morning meeting.

Officials have their eyes on the weather forecast and the dam at Coralville Lake, which is managed by the Army Corps of Engineers.

The lake is currently projected to crest at 705.34 feet above sea level on July 8. The emergency spillway is at 712 feet. Water has only ever topped the spillway in 1993 and 2008.

Following a request from local officials, the Corps on Wednesday increased the amount of water released from the lake to 8,000 cubic feet per second, said lake operations manager John Castle. The Corps' strict guidelines put the normal maximum outflow for this time of year at 6,000 cfs, although outflow typically doesn't exceed 2,000 cfs, he said.

Some local officials would like it even greater. Leaders from the cities of Iowa City and Coralville and the University of Iowa wrote the Corps a letter June 28 saying they were concerned about the height of the lake and the weather forecast and asked that outflow be increased to 10,000 cfs as soon as possible.

Dubuque Street in Iowa City starts flooding at 12,000 cfs, Wilson said. Outflow hit a record 39,500 cfs in June 2008.

Castle said outflow was increased because of the potential for heavy rain next week.

That forecast is still in question, said Mike McClure, a meteorologist with the National Weather Service in the Quad Cities, but 4 inches or more of rain could hit the Iowa River watershed next week.

“It's really hard to say at this point because it's so far out there,” he said.

It looks like the remnants of Hurricane Alex will come to the Midwest and weak winds will make the storm slow-moving, he said. It's not yet clear where the storm will settle. Some models show it in central and western Iowa and some put it farther east, McClure said.

Rivers are not a problem at this time. The Iowa River in Iowa City is three feet below flood stage and holding steady, according to the National Weather Service. Minor to moderate flooding is forecast for Columbus Junction and Wapello.

The Corps' computer models indicate that if the entire watershed receives up to 3 inches of rain next week, Coralville Lake would peak at 708 feet on July 16, said Rick Fosse, Iowa City's public works director.

That would consume about half the lake's remaining capacity, he said, meaning it could handle more rain.

“That gives us a good comfort level for the early part of next week,” he said, adding there was no need for alarm at this time.

City officials are concerned enough, however, that they're reviewing their plans for dealing with serious flooding, he said.

UI officials are monitoring the situation closely and have also asked staff to review flood plans, said spokesman Steve Pradarelli.

Wilson said emergency management has 750,000 sandbags ready to go. The emergency operations center starts activity when the lake hits 706 feet and is fully operational at 709 feet, he said.

Also Thursday, Johnson County's supervisors gave Wilson the OK to gauge the interest of other local officials in requesting a study of the Corps' policies for Coralville Lake.

The study likely would cost more than a million dollars to be split by the federal and local governments. The current guidelines have been in place since 1992, Castle said.

The Corps is in favor of a new study, he said, but local officials have shied away from doing one in the past because of the cost.

Wilson said he thought moving the start of the lake's summer schedule to a later date would be beneficial. The 6,000 cfs maximum starts May 20 to avoid flooding farm fields downstream, Castle said.

A commonly heard criticism is that the Corps keeps lake levels too high for recreational reasons. Democratic Sen. Tom Harkin made that claim Thursday when talking about the reservoirs at Saylorville, Red Rock and Coralville lakes.

“I'm concerned that the release rates earlier this spring were not sufficient in order to plan for a possible flooding condition,” he said.

But Castle said that of Coralville Lake's five authorized uses, the top priority is flood control and No. 5 is recreation.

The Gazette's James Q. Lynch contributed to this report.

RELATED INFORMATION:

RELATED INFORMATION:

• Flood maps from the Iowa Flood Center
• Maps help predict flood waters
• Rainfall totals for June