Historic floods push Minnesota dam on the brink of failure; heatwave bakes Central US


Historic flood in the Midwestern U.S. in recent days has caused widespread damage and has pushed Minnesota's Rapidan Dam to the brink failure as officials warned residents of potential evacuations on Monday.

Across the northern and central Plains, communities reeling from record-breaking floods over the weekend remained under threat of rising rivers as floodwaters headed downstream and forecasts project more rain this week. Floodwaters breached the Rapidan Dam in southern Minnesota and local officials warned Monday that the dam is in "imminent failure condition."

Authorities asked residents to watch out for possible evacuations. Blue Earth County Emergency Management said it was made aware of "accumulating debris" at the dam on Sunday, which is currently being monitored by Blue Earth County Public Works and law enforcement.

"We do not know if it will totally fail or if it will remain in place, however we determined it was necessary to issue this notification to advise downstream residents and the correct regulatory agencies and other local agencies," the Blue Earth County Sheriff's Office said on Facebook early Monday.

By Monday afternoon, the sheriff's office reported a "partial failure" of the dam on the west abutment but noted that the dam was still intact and there were current plans for a mass evacuation. Residents who were in "imminent danger" were notified, according to the sheriff's office.

Scattered, fast-moving showers were slated to impact the region early this week before more organized thunderstorms bring heavy rain by Thursday, according to the National Weather Service. Last week, parts of the region were hit with a month's worth of rain in a span of 48 hours. Sioux Falls, South Dakota, received 6.33 inches of rain from Thursday to Saturday, with 10.8 inches of rain so far in June, AccuWeather said.

"So much rain has fallen in a zone from southwestern Minnesota to northeastern Nebraska, including northwestern Iowa and southeastern South Dakota, that multiple rivers are on the rampage," said AccuWeather Senior Meteorologist Alex Sosnowski.

Meanwhile, heat advisories warning of potentially record-breaking temperatures remained active on Monday across a vast swath of the U.S. Tens of millions of people across the country, from South Dakota to Texas to parts of northern Florida and Georgia, face heat indices – temperatures that take humidity into account – in the high 90s and up to 110 degrees, according to the weather service.

Minnesota dam breached by floodwaters

On Monday, the department of emergency management in Le Sueur County said the Rapidan Dam was "breached," and urged residents to prepare for potential evacuations. The dam is located downstream from Mankato, Minnesota, about 80 miles southwest of Minneapolis.

"Residents of Le Sueur County in low-lying areas of MN River Valley communities of Kasota, Le Sueur, St. Peter and Ottawa are advised to closely monitor situation and potentially evacuate. This does not effect residents of Waterville or surrounding area."

The Blue Earth County Sheriff's Office said in an update Monday afternoon that a portion of the river flow was diverted "around the west side of the dam and water continues to flow."

Authorities evacuated homes on Birch Avenue and Neubert Lane, which is just northwest of the dam. Various roads in Mankato were also closed due to flooding.

North Mankato declared a flood emergency earlier as city crews rushed to construct a temporary earth wall levee, city officials said in a Facebook post.

An Xcel Energy substation at the dam was washed away early Monday after heavy rain over multiple days caused the Blue Earth River to flood. The utility company said nearly 600 customers were without power as a result and crews were working to replace the substation and restore power.

A U.S. Geological Survey gauge tracking water in the area also lost power, according to the weather service.

Minnesota Gov. Tim Walz said on Monday afternoon agencies are in close contact with county and local officials about the dam. "Emergency management is on the ground and acting quickly to ensure the safety of Minnesotans as the situation develops," he posted on X.

Water flow of Minnesota river rapidly increased over the weekend

Water flow in the Blue Earth River at the dam grew by 3.5 times between Friday morning and Monday morning, its flow increasing from 9,530 cubic feet per second to 34,500 cubic feet per second, according to USGS data.

The river’s height at the gage rose from 8.2 feet at 5 a.m. on Friday to 16 feet at 10:30 p.m. on Sunday. By Monday morning, it had risen another two feet, the third-highest level on record.

The record height was set at 23.63 feet on Jan. 18, 2020, according to the USGS data. The previous record height had been 21.36 feet on April 9, 1965. Records for the location date back to at least 1951.

The Rapidan Dam was constructed between 1908 and 1910 and measures about 475 feet in length and about 87 feet from the top of the dam to the stream bed, according to the Blue Earth County government website.

High temperatures continue in parts of U.S.

Lows will mostly remain in the mid-to-upper 70s, "bringing little relief from the heat overnight," the weather service said.

Meanwhile, east-central South Carolina could experience a heat index of 110 degrees, and a stretch of Southern California is forecast to bake under temperatures between 90 to 100 degrees on Monday.

"The arrival of this more intense heat early in the Summer season leads to a higher level of heat-related stress, especially for those outdoors and without reliable air conditioning available," according to the weather service.

The shift west for the scorching heat comes as a cold front brings relief to millions across New England and the mid-Atlantic regions, where record-breaking afternoon highs reached the high 90s and surpassed 100 degrees throughout last week and over the weekend.

The heat will bear down on the central U.S. before concentrating mostly on the South by the latter half of the week, the weather service said.

Hundreds rescued; nearly 2K buildings damaged in Iowa floods

Between Friday and Sunday, some areas of northwest Iowa – where the ground was already saturated – recorded up to 15 inches of rain, a deluge that damaged public infrastructure and triggered hundreds of evacuations and rescues. At least 16 flood gauges recorded historic river levels as waterways across the northwest region of the state rose several feet above previous record levels.

At least 250 people were rescued over the weekend while 1,900 properties were "impacted" and hundreds were destroyed, said Iowa Gov. Kim Reynolds at a news conference on Sunday.

Iowa Gov. Kim Reynolds speaks during a news conference addressing the flooding in northwest and north central Iowa on Sunday at the Iowa National Guard Joint Forces Headquarters in Johnston.
Iowa Gov. Kim Reynolds speaks during a news conference addressing the flooding in northwest and north central Iowa on Sunday at the Iowa National Guard Joint Forces Headquarters in Johnston.

"The devastation is severe and it's widespread," Reynolds said. "While we're still very early in the response, the projected damage is staggering."

Officials reported at least 10 city water systems and 21 waste water systems have been disrupted by the floods, leaving many residents without drinkable water. Well over 1,000 Iowans took to shelters over the weekend.

John Benson, Iowa director of Homeland Security and Emergency Management, said at the news conference the "flood" is not over, warning that as the water recedes, much of it will flow into larger waterways, including the Missouri, Big Sioux, South Fork and Mississippi rivers, which are expected to reach "major flooding" stages in the coming days. The expected rain this week only adds to the flood threat.

"(The flooding) is not going to cease, it is going to blossom across the state," Benson said.

Contributing: Gabe Hauari, Cybele Mayes-Osterman, Dinah Pulver, USA TODAY

This article originally appeared on USA TODAY: Heat wave to bake central US as Plains faces more rain, flooding