By Michael Avok
HAMBURG, Iowa (Reuters) - A levee on the flood-swollen Missouri River near Hamburg, Iowa failed on Monday, prompting the National Weather Service to issue a flash flood watch for the town of 1,200.
In addition to Hamburg, areas threatened with flooding as a result of the failure include parts of Interstate 29 and the rural residences and county roads located between the Missouri River and Hamburg, the NWS said.
"The full breach is 50 feet wide and occurred in approximately five minutes," the U.S. Army Corp of Engineers said in a statement, adding that workers present on the levee evacuated safely.
R.D. Hendrickson, in town from Phoenix to help his family prepare for possible flooding, witnessed the breach Monday morning, which took place south of the downtown in an area of farms.
"It was surreal to see the river take the levee out," he told Reuters.
"I think it was a sand boil. The water was shooting out of the ground straight up and it just cut the levee out ... Farmers lost their entire crop out there on this one."
Downtown Hamburg remained completely dry, nearly three hours after the levee failed, with some businesses, like the Hendrickson family's Blue Moon Grill & Bar on Main Street, still open for business -- though surrounded by sandbags 12-feet tall.
"Our drugstore and our little bakery on the corner are open, too," Wilma Hendrickson, the family's 77-year-old matriarch, told Reuters.
But city officials warned those who stayed behind that within 24 hours the waters would reach a secondary berm hastily built in recent days to protect the city, and that power was likely to be quickly lost when they did.
"Things are going to happen fast, I think," said Wilma Hendrickson's daughter, Vicki Julin. She said the family's bar, open since 1972, had "been a watering hole for a long time. Now it's literally going to be a water hole."
The emergency response appeared to be focused for now to the area south of the city, where Hendrickson said customers and other family members had told her the floodwaters were "filling in rapidly ... it's bad."
Earlier this month, another nearby levee was breached, prompting officials to warn residents of low-lying areas around Hamburg to get out.
Since then, workers scrambled to build another protective berm around the city in anticipation of continued flooding on the Missouri.
The Corps said reinforcement and completion of that berm and others to limit flooding of the town were continuing.
"We have contractors in place and are working expeditiously to raise Ditch 6 levee near Hamburg by an additional four feet" to protect the town, the Corps said.
The Missouri, a major tributary of the Mississippi River system, is expected to rise to record levels and stay there for weeks and possibly months. Heavy winter snowmelt at its headwaters in the Rocky Mountains, as well as heavy spring rains, have forced the Corps to release water from stressed reservoirs and dams up and down the river.
The flooding along the Missouri has already displaced thousands of people in South Dakota and threatens to add to the misery downstream in the Mississippi Valley, where record floods earlier this year caused billions of dollars in damage.
Ultimately, the Corps plans water releases to peak at a rate of 150,000 cubic feet per second from the five reservoirs in the Dakotas by about mid-June, more than twice the previous record pace, and hold at least through mid-August.
The Missouri River basin forms the northwest portion of the Mississippi River basin that stretches from Montana to western New York and funnels water south into the Gulf of Mexico.
The river is expected to reach up to seven feet above flood stage at Sioux City, Omaha and Kansas City when the maximum release rate is reached.
(Writing by James B. Kelleher; Editing by Jerry Norton)