By David Bailey
MINNEAPOLIS (Reuters) - Stretches of the rising Missouri River in South Dakota were closed to boaters by Wednesday to protect newly built levees, while the states of Iowa, Nebraska and Missouri downstream rushed to prepare for the flood.
The U.S. Coast Guard has closed the river to recreational traffic for 260 miles from where Iowa, Missouri and Nebraska meet at its southern point, to the Gavins Point Dam in South Dakota.
Water releases from the Gavins Point Dam are closely watched by communities all the way to the Missouri River's confluence with the Mississippi River at St. Louis because it is the release point for the last reservoir on the river.
Heavy rains in May across Montana and North Dakota at the upper reaches of the river, coupled with a deep melting winter snowpack, have left reservoirs near capacity from Montana through South Dakota, the U.S. Army Corp of Engineers said.
The Corps has planned to double previous record release volumes to bring down reservoir water levels. It expects to reach maximum planned release rates by mid June and hold those rates through at least mid August.
The Corps on Tuesday night said it had raised its maximum planned release rate from the Fort Peck, Montana, reservoir to 55,000 cubic feet per second from 50,000.
The increase at Fort Peck is not expected to force any change in the planned maximum release rates at the other five reservoirs, which are expected to reach 150,000 cubic feet per second by about mid June.
Overall, thousands of residents in North Dakota and South Dakota have voluntarily left flood-threatened areas.
Sandbags and berms were going up along the river in Iowa, Nebraska and Missouri. In Iowa, parts of Interstate 29 that runs parallel to the east bank of the river were expected to be closed as flows peak later in June.
Contractors raced to build a secondary levee to protect the south side of Hamburg, Iowa, now threatened by a failing levee miles to the south on the swelling Missouri River. Hamburg is in the southwest corner of Iowa near Missouri and Nebraska.
A partial breach in that levee was patched by sandbags dropped from a helicopter over the weekend. Federal officials expect the fix to hold until the secondary levee is finished, but not to withstand the full might of the river's crest.
The Corps believes more levee breaches on the lower Missouri River are likely given the varying strengths of the flood protections and the height, speed and duration of planned releases of water from reservoirs.
Miles north of Hamburg in Nebraska City, Nebraska, dirt and sand were stacked more than eight feet high around a gas station and a fast-food restaurant.
In Bellevue, Nebraska, just south of Omaha, water reached up nine feet, touching the nets on the basketball hoops in a city park along the Missouri River.
North of Omaha, in Washington County, authorities restricted civilian river traffic after reports of looters trying to take items from abandoned homes.
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.
Sandbagging continued on Wednesday in northwest Missouri. In Parkville on the edge of Kansas City, residents were resigned to flooding and the city asked for volunteers to fill 40,000 more sandbags to protect downtown streets.
"It's going to happen, we know it's going to happen," said Pam Todd, who was fielding calls while Parkville city officials toured levees. "Everyone remembers 1993 and so many volunteers have come out. Every entity you can think of is helping us."
(Additional reporting by Michael Avok in Hamburg, Iowa, and Kevin Murphy in Kansas City)