UPDATE: The news for flood-weary residents in Johnson County keeps getting better, officials said Monday, announcing that the swelling Coralville Lake likely will crest two feet short of topping the spillway.
But communities, residents, businesses and the U.S. Army Corps of Engineers still are making preparations and taking precautions as the lake and the Iowa River in Iowa City have not yet peaked.
“A little rainfall can change a whole lot of things,” said Dee Goldman, Coralville Lake operations manager for the U.S. Army Corps of Engineers.
The Coralville Lake’s elevation was expected to reach 708.53 feet by the end of the day Monday, and its projected crest at 709.82 feet is anticipated on Thursday, according to the Corps’ forecast. Water pours over the lake’s spillway at 712 feet, in which case downstream communities experience an uncontrolled flow.
The Corps opened the dam’s gates all the way over the weekend, increasing the outflow to 18,400 cubic feet per second by Monday morning. Because the lake’s elevation is not expected to climb as high as originally thought, the flow is expected to max out at about 19,000 cfs, rather than 20,000 cfs, according to Goldman.
South of the lake, he said, flow numbers will increase by about 1,000 cfs, due to additional tributaries. The Iowa River in Iowa City is expected to crest at 25.1 feet on Tuesday, according to the National Weather Service.
The river’s flow into the Coralville Lake is at about 30,000 cfs, mostly from where the Iowa River passes through Marengo. The inflow will continue to drop slowly until Saturday, and then it will fall faster, said Terrence Neuzil, spokesman for the Johnson County Emergency Management Agency.
“It will significantly after the 8th (of June) – up to a foot a day,” Neuzil said.
Even with big drops in the inflow, Neuzil warned, “This is going to be a prolonged event.”
The “comfort level” for Coralville Lake levels in the summer is 683 cfs, and Neuzil said the elevation will remain above that through June. That has emergency and lake officials turning their concerns toward public safety, and the Corps of Engineers announced today that it will close the road that passes over the Coralville Dam.
Beginning at 10 p.m. Monday, the Corps is closing West Overlook Road NE – just before it heads down the hill toward the spillway – to the Corps’ office on the other side of the dam, after the road becomes Prairie Du Chien, according to Goldman. The popular passage will remain closed until further notice – probably until sometime after Saturday, Goldman said.
The closure was prompted by a huge number of sightseers who have migrated to the dam in recent days to see the flood water, according to Goldman. Keeping visitors away will help officials both maintain safety in the area and do routine inspections of the dam and its functions.
“It’s a manmade structure, and if there are any changes, we want to make sure they are from Mother Nature and not from someone else,” Goldman said, adding that the closure is “paramount for dam safety.”
Increased vehicle traffic also has caused problems in the area, he said, noting an accident in the area Sunday that backed up the flow of people and made it more difficult for the corps to do its job.
Safety on the lake is a concern as well, Goldman said. Boating and recreating on the reservoir have not been banned, but Goldman said people are advised to stay away until water levels drop, and many have ignored that advice.
“Boat traffic has been picking up because people are feeling more comfortable,” Goldman said. “But there still is debris coming down the river.”
Submerged sticks, logs and other material can make waterskiing and tubing incredibly dangerous, he said.
Shawn Meier, with the Iowa Department of Natural Resources, said crews have halted construction on the Mehaffey Bridge, where it crosses the Iowa River by the Coralville Lake. But, he said, construction debris and even chemicals and hazardous material could come down the waterway.
“There were reports of people playing in the water as of last night,” he said.
Johnson County Sheriff Lonny Pulkrabek said he heard a recent report of people putting in a canoe in the Iowa River in Iowa City before police made them get out. And, he said, some people also were wading in backwater Monday morning.
But no citations have been issued to individuals for ignoring the ban on recreation along the Iowa River, south of the lake, he said.
Johnson County officials still estimate that about 60 structures have been or could be affected by floodwaters, causing millions of dollars in damage. But the University of Iowa, Coralville and Iowa City all have reported confidence in their current levels of preparation.
Several businesses in Coralville that have prepared for the worst are optimistic the flooding will be far from that.
“We are excited about the good reports – we are very happy,” Maja Hunt, co-owner of Every Bloomin’ Thing in Iowa City, said Monday after moving much of her inventory out over the weekend. “We kind of feel like we had a practice run at evacuating.”
The staff is still operating out of the store – preparing for its three weddings this weekend – but Hunt said they’re ready to go if rain changes the outlook later this week.
“We are not moving back in yet,” she said. “They told us that we should wait until after the 9th or so before we think about moving back in.”