The U.S. Army Corps Of Engineers is warning of historic releases from Missouri River reservoirs and predicting significant flooding in cities, towns and agricultural land in North and South Dakota. Officials say the river in many areas from Sioux City, Iowa to the Mississippi River will rise well above flood stage. The releases are forced by record winter snowfall and a year’s worth of rain in the last month in some areas.
By the end of June, river stages 3-6 feet above flood stage are expected from just below Sioux City to the mouth north of St. Louis.
Officials are encouraging people along the river to make evacuation plans to protect their possessions and property. Flooded areas are expected to be inundated for several months. Maps of potential flood areas are available here, and from local emergency management offices.
In a news release, the Corps announced flows from Gavins Point Dam will reach a record 110,000 cubic feet per second (cfs). The previous high releases were 70,000 cfs in the fall of 1997.
In the last month, the upper basin has received a year’s worth of rain.
“The amount of rain has nearly filled the reservoirs, doing away with most of the flexibility we had built into our operations for this year,” said Jody Farhat, Chief of the Water Management Division here. “With the arrival of the 140 percent-of-normal snowpack runoff, all the reservoirs will reach their maximum levels.”
“Moving water out of the reservoirs is essential to prevent the spillways from being overtopped which would make flooding much worse,” said Brig. Gen. John McMahon, commander of the Northwestern Division of the Army Corps of Engineers.
“Our release plan is based on the rain we’ve already received and the forecasted snow melt. More heavy rain storms could cause major revisions.”
At these levels, additional releases do not significantly change the foot print of the flooding, only the depth.
Releases Fort Peck, Mont., are expected to reach 40,000 cfs in early June and peak at 50,000 cfs in early July. The reservoir is forecast to reach within a foot of the top of the spillway gates.
Garrison releases will increase from the current 75,000 cfs to 85,000 cfs on Monday, May 30 and reach 105,000 cfs about mid-June. The peak reservoir level will likely reach the top of the spillway gates at 1853.9 feet. Many areas along the river in the Bismarck-Mandan area will be flooded with 3 to 6 feet of water.
Oahe releases will follow a pattern similar to Garrison, reaching 85,000 cfs on Saturday, May 28 and as high as 100,000 cfs by June 6 and 110,000 cfs by late in the month. The reservoir will peak within a foot of the top of the spillway gates at 1619 feet. Many areas along the river in Pierre will be flooded with 2 to 6 feet of water.
Big Bend releases will mirror those from Oahe, with its reservoir level remaining at 1420 feet.
Releases from Fort Randall will gradually increase from the current 61,000 cfs to 110,000 cfs by late-June. River stages in the reach below the dam should rise 2 to 6 feet.
Releases from Gavins Point will gradually increase from the current 63,000 to 110,000 cfs by the end of June.