HAMBURG, Iowa, June 13 A levee on the flood-swollen Missouri River near Hamburg, Iowa failed on Monday, sending water into low-lying farmland and prompting a flash flood watch for the town of 1,200, authorities said.
The U.S. Army Corps of Engineers said the fight against the rising waters, which is expected to drag on for weeks, would be complicated in the coming days by thunderstorms, some expected to drop as much as 5 inches (13 cm) of rain in places.
Monday's breach in the levee built in the late 1940s was 300 feet (90 meters) wide, the Corps said in a statement. The workers who were on the levee were evacuated safely.
In addition to Hamburg, areas threatened with flooding as a result of Monday's levee break include parts of Interstate 29 and the rural residences and county roads located between the Missouri River and Hamburg, the National Weather Service said.
R.D. Hendrickson, in Hamburg from Phoenix to help his family prepare for possible flooding, witnessed the breach on Monday morning south of the town in an area of farms.
"It was surreal to see the river take the levee out," he said.
"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, located about 5 miles (8 km) away from the breach, remained dry six hours after the levee failed but vulnerable because of its low-land topography.
City officials were warning those who stay behind that within 24 hours the waters would reach the secondary berm hastily built in recent days to protect the city, and that power was likely to be quickly lost when they did.
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.
Heavy winter snowmelt feeding the river's 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 this spring caused billions of dollars in damage. (Writing by James B. Kelleher; Editing by Peter Bohan)