MINNEAPOLIS (Reuters) - The rapidly rising Souris River poured over flood defenses in Minot, North Dakota on Wednesday, overwhelming efforts to delay the deluge and forcing immediate evacuation of thousands of residents.
City officials had ordered a mandatory evacuation of a quarter of North Dakota's fourth largest city, but the massive water flows from heavy rains in Canada hastened the evacuation by about five hours as defenses began to fail.
Up to 12,000 residents live in areas expected to be swamped by floodwaters projected to smash a 130-year-old record by up to 5 feet. Emergency sirens sounded about 1 p.m. indicating that water was flowing over levees in flood-threatened areas.
"We are trying to patch up as many holes as we can to give people as much time as we possibly can to get them out safely," said Dean Lenertz, a Minot Fire Department captain and spokesman.
The Souris River has already reached roughly the same level at the Broadway Bridge that it had in the 1969 flood local residents used as a benchmark for evacuation. It is projected to beat that mark by up to 8 feet.
The National Guard found "several areas of concern" in the morning, forcing the earlier evacuation. Officials had warned residents of the possibility and had urged them to map out a direct route to higher ground if the warning sirens sounded.
Heavy rains over the past six weeks have swelled Canadian reservoirs in the Souris River basin, forcing unprecedented water releases. In turn, U.S. officials must release water from the Lake Darling Dam above Minot at a rate more than double what the recently fortified protections can bear.
The U.S. Army Corps of Engineers started building temporary levees in Minot in April, spokeswoman Shannon Bauer said.
"We have raised them three or four times, but there is just not enough time to raise them any higher," Bauer said in a telephone interview. "Also, they are saturated. If you add more material to them they won't last."
As many as 5,000 buildings in Minot are threatened by the flooding that could keep the area inundated for two weeks or more, officials said.
A National Weather Service flash flood warning Wednesday extended from Burlington, through Minot and Logan and Sawyer.
The massive flooding on the Souris River, which flows into the Red River basin, was the latest problem as flooding threatens communities from Montana through Missouri.
The swelling Missouri River threatens the North Dakota capital of Bismarck, the South Dakota capital of Pierre and other communities for hundreds of miles downstream.
North Dakota Governor Jack Dalrymple had thanked residents in the Bismarck area for offering surplus sandbags and other aid to Minot.
"I never thought we could possibly have anything even coming close to what is happening in Bismarck-Mandan this year ...," Dalrymple told reporters in a briefing. "There will be a lot of water in the city."
The U.S. Army Corps of Engineers plans to step up releases from the Lake Darling Dam and to 15,000 cubic feet per second on Thursday. Flood defenses in Minot were rated to perhaps 9,500 cubic feet per second, officials have said.
The Corps expects peak releases to reach about 20,000 cubic feet per second by late June and hold there for up to six days before a gradual reduction back to below 8,000 cubic feet per second over five days.
Amtrak suspended Empire Builder service Tuesday in part of Minnesota, North Dakota and eastern Montana due to flooding.
Heavy rains added to woes across the Missouri River basin from Montana through Missouri earlier this week and forced federal officials to adjust planned water release rates from some of its six reservoirs on the Upper Missouri River.
The Corps plans to reduce some releases to allow flows from tributaries to pass, but will increase the expected maximum at the key Gavins Point Dam on the South Dakota-Nebraska border. Rates already are roughly double the previous record.
The Missouri River runs freely from Gavins Point for more than 800 miles to the Mississippi River near St. Louis, making the releases from the dam a focus for downstream residents.
The Corps plans to increase water releases at Gavins Point to 155,000 cubic feet per second on Wednesday and to 160,000 on Thursday. It plans to hold peak releases at least through mid-August.
Levee failures have forced mandatory evacuations of several towns near the Missouri River and the heavy rains and increased releases added to local concerns.
Residents in the village of Bigelow on Wednesday were among the latest mandatory evacuations in Holt County, Missouri, due to Missouri River levee failures or expected failures.
The village of 30 people was being evacuated while roads are still passable, following by one day the evacuation of the 300 residents of Craig, Missouri, due to levee breaches.
"There are two levees today that we fully expect could breach at any time," said Kathy Kunkel, clerk of Holt County who is helping oversee emergency operations.
Additional reporting by Kevin Murphy in Kansas City; Editing by Greg McCune