Archive for Friday, July 29, 2011

Missouri River flooding will last until autumn in some places

July 29, 2011, 2:41 p.m. Updated July 29, 2011, 5:52 p.m.


— The Army Corps of Engineers plans to begin reducing the amount of water being released from dams into the swollen Missouri River in August, but flooding will likely linger into the fall in parts of Iowa, Nebraska and Missouri, officials said Friday.

The corps will gradually reduce the amount of water being released from upstream dams to decrease the risk of damage to levees, but it will try to coax the river back into its banks in flooded areas as soon as possible so that repairs can be made, Brig. Gen. John McMahon said.

"We have a record amount of water to evacuate from the system and very little time to do that before winter," McMahon said.

The corps has been releasing massive amounts of water from the six dams along the river to deal with heavy spring rains and above-average mountain snowpack.

McMahon defended the way the corps has managed the river this year because he says no one anticipated the amount of water the agency would have to deal with. He said the lessons from this extraordinary year will be applied in the future.

"We're doing the best we can based on the information we have at the time," said McMahon, who is commander of the corps' Northwest Division.

Areas upriver will see relief from flooding sooner, as the releases begin to clear more space in the reservoirs and the floodwaters drain off of the flood plain back into the river. People in Nebraska, Iowa and Missouri will have to wait until September or October for that.

Officials predict the river will fall below flood stage in the Sioux City, Iowa, area in late August. Near Omaha, the river will fall below flood stage by mid-September, and the flooding near Rulo, Neb. and Hamburg, Iowa, should end by late September.

Flooding along the river in Missouri may not end until around mid-October because several levees failed in the northwest corner of the state and allowed a large amount of floodwater to accumulate.

South Sioux City officials are grateful that a 7,000-foot-long levee completed shortly before the floodwaters arrived in June has held up. To date, only 39 homes have been damaged by the flooding, but much of the city's parks along the river have been devastated by floodwaters and more damage will be exposed when the water recedes.

Still, City Administrator Lance Hedquist feels good about how the northeast Nebraska city fared.

"The vast majority of the town is still high and dry," Hedquist said. And officials are already making plans to replace 75 acres of grass and about 800 trees that were lost.

Downriver in Hamburg, business owner Terry Holliman said he had been expecting the floodwater to linger until fall so the he wasn't surprised by the corps' announcement.

Holliman had to move his auto parts store several blocks up main street to a spot on higher ground because of the flooding, but he's glad the town of about 1,100 residents has remained dry. After levee breaches in northwest Missouri just a few miles south of Hamburg, the corps built a secondary levee to protect the town.

"We've got 5 feet of water around town, but none in it," Holliman said.

Everyone in Hamburg is just biding their time until the floodwaters are gone.

"The losses are just going to be astronomical when this water recedes," Holliman said.

The corps said it plans to reduce the amount of water flowing out of Gavins Point dam near Yankton, S.D., from 160,000 cubic feet per second to 150,000 cubic feet per second this weekend. But the releases will be held at that level until mid-August.

Around Aug. 15, the releases from Gavins Point will begin being gradually cut each day to reach the target of releasing 90,000 cubic feet of water per second by the end of August.

That will lead to a drop of 4-to-6 feet in the river level downstream, but the corps plans to maintain releases at the 90,000 level until mid-September so the levees and dams can be assessed.

Then the releases from Gavins Point will be slowly scaled back to 40,000 cubic feet per second by Oct. 1. The releases from the other dams further upriver will be reduced sooner.

This release schedule was one of eight different alternatives officials considered as they tried to balance how long they kept the water high against how much time they needed for repairs before winter. Plus, officials know that the longer the floodwaters put pressure on the levees, the greater the chance of failure becomes.

The corps ultimately decided not to clear out any additional flood-storage space in the reservoirs beyond the normal amount, so they could bring an end to the flooding sooner.

"The assessment is that what we have seen in 2011 is a 1-in-500-year event, so there is a very low probability of it occurring again," McMahon said.


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