MINNEAPOLIS (Reuters) - Residents evacuated some affluent areas of North Dakota and South Dakota on Friday along the swollen Missouri River as federal officials kicked up water releases to relieve pressure on six Upper Plains reservoirs.
About 400 residents of upscale neighborhoods on the river in Bismarck, North Dakota’s capital, were evacuating and South Dakota Governor Dennis Daugaard urged residents of the “country club” area of Dakota Dunes to exit by midnight.
In Bismarck, workers were nearing the end of a race to finish a series of levees on Friday as federal water managers ramped up spills upstream from Garrison Dam, officials said.
Mayor John Warford said Bismarck was approaching the eleventh hour and urged residents to “focus on the fight.”
Voluntary evacuations were largely complete from lower lying areas of Pierre, South Dakota’s capital, and nearby Fort Pierre that would flood if levees fail, Daugaard said.
The U.S. Army Corps of Engineers increased the water flow through the Oahe Dam above Pierre rapidly as planned on Friday morning. The river level is expected to rise about four feet as releases accelerate to maximum planned levels by Tuesday.
Eric Stasch, Corps operations manager at the Oahe Dam, said the Corps planned to increase flows in two stages on Friday and Saturday to “make these rises a little more manageable.”
Heavy rains coupled with a deep melting snowpack have swelled Missouri River reservoirs from Montana through South Dakota to near capacity.
Flows from most Missouri River reservoirs already were at record levels on Friday and the accelerated releases will add several feet to the high river levels deep into July.
Residents in Nebraska, Iowa and Missouri also were braced for widespread flooding. The maximum planned release rates are expected to push the Missouri River up to seven feet above flood stage at Sioux City, Omaha and Kansas City.
The governors of Missouri, Iowa and Nebraska have been surveying areas already flooding along the Missouri River.
“The Misssouri River will be high for the rest of the summer,” said John Grothaus, chief of planning in the Corps’ Kansas City district.
Officials stopped short of mandatory evacuations in South Dakota. Up to 3,000 Pierre and Fort Pierre residents and more than 800 of the 1,100 homes in Dakota Dunes are threatened.
Police and National Guard members will go door-to-door in Dakota Dunes to warn residents who stay that the risks will rise with the water, utilities will be cut off eventually and they may not be able to leave later, Daugaard said.
A primary levee in Dakota Dunes was nearly done on Friday and the Corps expects a backup levee to be finished Tuesday.
In Montana, the Corps increased water flows from Fort Peck Dam, while widespread flooding of Missouri tributaries has forced hundreds of evacuations and inundated several smaller cities, including Roundup where workers were pumping Friday.
“We’ve had floods in the past, we’ve had disasters in the past, but we’ve never had anything that spreads from border to border like this,” said Monique Lay, spokeswoman for Montana Disaster and Emergency Services.
In the Red River valley system nearby, officials in Minot, North Dakota, said Friday they would evaluate daily whether to keep up a mandatory evacuation of 12,000 residents, or a quarter of the city, due to flooding along the Souris River.
The Missouri River basin forms the northwest section of the Mississippi River system that stretches from the Rockies to western New York in the north and funnels water down through Louisiana to the Gulf of Mexico.
The Corps held water in the Missouri reservoirs to reduce the impact from record Mississippi River flooding earlier this year. Mississippi flood stages are expected to be extended a few weeks by the releases, but not raised.
Additional reporting by Laura Zuckerman in Salmon, Idaho, and Kevin Murphy in Kansas City; Editing by Jerry Norton