01:03 ‘Total Disbelief’: Families Isolated as Isaias Washes Away Only Road to Their Homes Heavy rain and rising waters washed away a private road in Huntingtown, Maryland, stranding 7 families on the wrong side of the break.

At a Glance Offutt Air Force Base, home to U.S. Strategic Command, is fighting floodwaters.

Preparations were being made to shut down a nuclear power plant along the rising Missouri River.

Nebraska emergency management spokesman said there is no safety concerns at the plant.

A Nebraska farmer was killed trying to rescue a stranded motorist. Two others are missing.

Another Nebraska man was swept away by floodwaters in Iowa and later died. All along Midwest rivers Sunday, residents and officials prepared for flooding that already has killed at least two people, forced mandatory evacuations, breached dams and levees and flooded a military base.

Thurman, Iowa, began evacuations about 7:30 a.m. Sunday EDT as fast moving water approached the town in the southwest corner of the state. The National Weather Service said the flooding was likely the result of levee breaches on the Missouri River. Areas of other Iowa towns had already evacuated, including Hamburg, Percival, McPaul and Bartlett.

Shortly after 3 p.m. Sunday, water topped a levee west of Hamburg as residents filled sandbags to build a retaining wall.

(MORE: Offutt Air Force Base Inundated by Floodwaters; Runway Closed; 60 Buildings Damaged)

In St. Joseph, Missouri, where the river is expected to crest at 30.1 feet early this week, city officials asked volunteers to help fill sandbags. The goal, city spokesperson Mary Robinson told WDAF-TV, was to have 150,000 sandbags by Tuesday to add a 2-foot wall to the levee.

Farther downstream, the Missouri is expected to crest above major flood stage in Atchison, Kansas, and just below that stage in Leavenworth, according to the National Weather Service. In Kansas City, where banks and levees are higher, it’s projected to crest at 32.4 feet, which is just above minor flood stage.

(MORE: Before-and-After Images Show Ongoing Flood Disaster in Nebraska)

Earlier in the weekend, flooding from the Elkhorn and Platte rivers turned Nebraska's sixth largest city into "an island." Fremont, Nebraska, which lies about 40 miles northwest of Omaha and is home to more than 26,000 residents, was cut off from the rest of the state Saturday when two levees were breached northwest of the city. Volunteers have spent much the weekend filling sandbags and lining them up to block water , the Freemont Tribune reported.

Volunteers also helped set up shelters; Spanish teachers translated for those who didn't speak English, and cooks at the Hy-Vee grocery store worked with the American Red Cross to feed stranded people , the Omaha World-Herald reported. A pilot from Lincoln, Nebraska, landed at Freemont's airport to give three meat cutters at the WholeStone Farms plant a lift home, where they each had children waiting.

“As long as we can help other people, that’s what we’re doing,” Adam Hunnel said.

<img class="styles__noscript__2rw2y" src="https://s.w-x.co/util/image/w/ap19076697745566.jpg?v=at&w=485&h=273" srcset="https://s.w-x.co/util/image/w/ap19076697745566.jpg?v=at&w=485&h=273 400w, https://s.w-x.co/util/image/w/ap19076697745566.jpg?v=ap&w=980&h=551 800w" > The Elkhorn River consumes a section of western Douglas County Sunday, May 17, 2019, in Omaha, Neb. Hundreds of people were evacuated from their homes in Nebraska and Iowa as levees succumbed to the rush of water. (Jeff Bundy/Omaha World-Herald via AP)

Mike Wight, public information officer for the Nebraska Emergency Management Office, told weather.com they are keeping a close eye on the situation in Fremont.

The rising Missouri River in the town of Brownville, Nebraska, meant officials began preparing to shut down the Cooper Nuclear Power Station if it was needed, according to a press release.

Wight told weather.com there is "concern" for the nuclear plant but emphasized that it "is perfectly safe."

"We don't expect any safety issues but we do expect they will get flooding around them and if it gets too far they will shut it down," Wight said, adding that it will not be an "issue with power supply" because they can get power from other sources within the grid.

On Sunday, the Nebraska Public Power District said in a release the plant was still operating at 100 percent and the river's water level had been stable for six hours.

(MORE: Flooding Worsens in the Plains, Midwest)

On Saturday, Black Hawk helicopters were dropping 1.5-ton sandbags to protect wells that serve the city of Lincoln, home to more than 284,000 people. The wells are located on an island in the rising Platte River.

After surveying the extensive flooding from the air, Nebraska Gov. Pete Ricketts said in a Friday press conference that it was the "most widespread flooding damage we've had in the last half-century."

"Even when we were away from the water system, we saw that the fields were very saturated," he added.

<img class="styles__noscript__2rw2y" src="https://s.w-x.co/util/image/w/AP19073731322255.jpg?v=at&w=485&h=273" srcset="https://s.w-x.co/util/image/w/AP19073731322255.jpg?v=at&w=485&h=273 400w, https://s.w-x.co/util/image/w/AP19073731322255.jpg?v=ap&w=980&h=551 800w" > A man works his way through a flooded Galena Street as the Pecatonica River continues to rise in Darlington, Wisconsin, Thursday, March 14, 2019. (Dave Kettering/Telegraph Herald via AP)

The U.S. Coast Guard closed all traffic Friday on a 70-mile stretch of the Missouri River from 50 miles south of Omaha, Nebraska, to St. Joseph, Missouri.

A Nebraska farmer identified as James Wilke, 50, was killed Thursday after the tractor he was using to attempt to rescue a stranded motorist was carried away by floodwaters , the Omaha World-Herald reported. The incident occurred at Shell Creek near Columbus in eastern Nebraska.

A 55-year-old Nebraska man died Friday night after being trapped by flooding in Riverton, Iowa , the Des Moines Register reported. Aleido Rojas Galan of Norfolk, Nebraska, and two other men were in a car that was swept away by floodwaters. All three were rescued, but Galan died on his way to the hospital, the Fremont County Sheriff's office said. The other two men were recovering in an Omaha hospital.

Also in Nebraska, two other men are missing and presumed dead. Scott E. Goodman, 30, of Norfolk was seen at 4 a.m. Thursday on top of his car near a levee that failed. It was reported that he was later seen being carried away by a surge of water , according to the Norfolk Daily News.

A second, unidentified man may have been swept away Thursday when the Spencer Dam collapsed on the Niobrara River.

When the dam failed, it caused a large ice floe to jam a hole in a small electrical plant, where employees were working. No other injuries were reported. The failure also forced the evacuation of dozens of residents along the river.

Chunks of ice from the Niobrara, some up to 2 feet thick, crashed into a gas station, a storage facility and a garage in the town of Niobrara, Nebraska, the World-Herald reported. The ice was left in piles 6 to 10 feet high around town.

“It’s total devastation. The ice just destroyed everything,” said Laura Sucha, who lost the Country Cafe restaurant she has owned since 2015.

Also along the Niobrara, the three bridges that connected Boyd County to the rest of Nebraska were closed. The bridges south of Butte and Spencer were closed because of the flooding, and the so-called “Mormon” bridge in Niobrara washed away.

(PHOTOS: Historic Flooding Strikes Plains, Midwest)

So far, 38 locations in five states across the Midwest have set new flood crests, said weather.com senior meteorologist Jon Erdman , noting that the flooding that is a result of recent heavy rains and snowmelt will continue through the weekend.

As of Friday evening, emergencies had been declared by the governors of three states: Nebraska, Iowa and Wisconsin.