Torrential rainfall and record snowmelt are contributing to a slow-motion flood disaster along the Missouri River and its tributaries in the northern Rockies and northern Plains.


Residents of Montana and the Dakotas are enduring the worst of the floods, which are projected to continue at least through the remainder of June, according to Tom Gurss, a hydrologist with the Missouri Basin River Forecast Center in Pleasant Hill, Mo. "This is the worst flooding I've seen, and I've been working here for 20 years," he said.

Thousands of residents in the three states are facing evacuations.

South Dakota Gov. Dennis Daugaard warned the 2,500 residents of Dakota Dunes to move to higher ground, secure their homes and be prepared to evacuate by tonight. The flooding could last for weeks, he said, and the governor was considering mandatory evacuations for some areas.

"They should expect to be out of their homes for up to two months," Daugaard said.

Russ Riesen of Dakota Dunes said he and his wife had already moved most of their possessions to an apartment they rented in Sioux City, Iowa.

"We're going to sit it out up in the hills and hope everything works out," Riesen said. "With Mother Nature, you never know what's going to come."

Gurss said extremely heavy rain - with some spots picking up 8 to 10 inches - across Montana last week caused all of the rivers in the state to rise. The amount of rainfall during the past few weeks has equaled what typically falls during an entire year, according to the weather service.

In order to prevent major reservoirs along the Missouri River from overflowing, the Army Corps of Engineers is planning to release record volumes of water from each of the six major dams that make up the Missouri River Mainstem Reservoir System.

This spring's flood will be the most severe the region has seen since the river's reservoir system was constructed in the 1950s and 1960s, according to Jody Farhat, chief of water management for the Corps of Engineers' northwestern division.

To make matters worse, nearly all of Montana's major river basins east of the Great Divide are registering snow-water levels at 200% to nearly 600% above normal, according to Natural Resource Conservation Service data.

Weather service hydrologist Gina Loss in Great Falls, Mont., said that with cool spring temperatures persisting, the snow hasn't stopped falling.

"We're not even done accumulating snow, let alone getting rid of it," Loss said.