Vehicles sit stranded in flood waters in rural Missouri Valley, Iowa June 17, 2011. [Photo/Agencies]

KANSAS CITY - Several levees in northern Missouri were failing Sunday to hold back the surge of water being released from upstream dams, and officials and residents braced themselves for more breaches as the Missouri River dipped but then rose again.

In Nebraska, a flooding alert was issued for a second nuclear power plant, but officials said it was the least serious emergency notification issued and the public and workers are not threatened.

The alert issued by the Nebraska Public Power District for the Cooper Nuclear Station near Brownville, Nebraska, didn't stop the plant from operating at full capacity Sunday.

The Fort Calhoun Station, another nuclear plant along the Missouri River in eastern Nebraska, issued a similar alert June 6. That plant near Blair, Nebraska, has been shut down since April and will not be reactivated until the flooding subsides.

Jodi Fawl, spokeswoman for the Nebraska Emergency Management Agency, said water was flowing over a levee in the Brownville area and into farmland, but the levee was being built up to alleviate that.

A hole in the side of a Holt County, Missouri, levee continued to grow, deluging the state park and recreational area in Big Lake, a community of less than 200 people located 78 miles (125 kilometers) north of Kansas City.

The water - some from recent rain - started pouring over levees Saturday night and Sunday morning in Holt and Atchison counties, flooding farmland, numerous homes and cabins.

Jud Kneuvean, chief of emergency management for the US Army Corps of Engineers' Kansas City District, said the Missouri River dipped by almost 1 foot (30 centimeters) after the Big Lake breach in Missouri but that the water started to rise again by Sunday afternoon.

He said Big Lake is seeking permission to cut a relief hole in an already-damaged county levee to allow water trapped behind the levee to flow back into the river.

Most people left their homes well in advance of the flooding. Those who stayed were told Saturday night that water was flowing into the area.

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. 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.