Authorities said water -- some of it from recent rain -- began pouring over levees Saturday night and Sunday morning in Holt and Atchison counties, flooding farmland and numerous homes and cabins.
A hole in the side of a Holt County levee continued to grow Sunday, deluging the state park and recreational area of Big Lake, 78 miles north of Kansas City.
U.S. Army Corps of Engineers spokesman Kevin Wingert said engineers would monitor the overtopping to try to determine how much of an effect it will have on water flows downstream.
"It's too early to say what the full impact will be on it," he said.
Meanwhile, the Nebraska Public Power District issued a flooding alert Sunday for its nuclear power plant in southeast Nebraska as the Missouri River continues to rise.
Mark Becker, a spokesman for the Columbus, Neb.-based utility, said the "notification of unusual event" sent to the Nuclear Regulatory Commission was expected as the river swells above record levels. The declaration is the least serious of four emergency notifications established by the federal commission.
The plant was operating Sunday at full capacity, and there was no threat to plant employees or to the public, Becker said.
In Missouri, presiding Holt County commissioner Mark Sitherwood said U.S. 159 is closed south of Big Lake because water is pouring over the road, and most of the west side of the community is underwater.
"It's going through in one place that we know of and overtopped in numerous places and there is seepage everywhere," Sitherwood said.
He said most people evacuated well in advance of the flooding. Those who stayed were told Saturday night that water was flowing into the area. A few people live in cabins that have been built up and decided to stay, Sitherwood said.
"Everyone up here knows the routine," he said.
The Big Lake area, where water has been high for the past couple weeks, has experienced major flooding in three of the last five years. But Sitherwood said this year promises to be much worse following weeks of high flows and increasing releases from the main stem dams in Montana and the Dakotas.
"I know they wouldn't admit it, but this is a manmade event," said Sitherwood, echoing a sentiment common in the area that the Army Corps of Engineers is mismanaging the Missouri River. "Nobody is going to tell me it isn't. It is probably going to be historical."
Sitherwood said his own home is at risk.
"Thank you, Corps of Engineers," he said.
The corps has said unusually heavy rains, not mismanagement, are to blame.
"What we are dealing with is a massive weather system that put a lot of precipitation in the system particularly in Montana and northern Wyoming in the month of May," Wingert said.
"The end result is that water has to go somewhere."