Highways close as rivers rise across southern Minnesota. More storms in forecast
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Rivers across southern Minnesota continued rising Tuesday, leading to highway closures — with more rain in the forecast.
Meanwhile, across northern Minnesota, a line of storms packing winds in excess of 65 mph knocked down trees and power lines early Tuesday.
Another round of strong, possibly severe thunderstorms is possible across the state Tuesday afternoon and evening.
River flooding
The Minnesota River is among the southern Minnesota waterways on the rise in the wake of recent heavy rain.
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The Minnesota Department of Transportation said State Highway 19 east of Henderson will likely close Tuesday as the river continues to rise.
Sibley County has closed County Highway 6 north of Henderson, too. And State Highway 93 south of Henderson is closed as MnDOT works to raise the roadway for a long-term flood fix —but that work won’t be done until 2026.
That leaves Highway 19 west of Henderson as the only main route to and from town until the river recedes — meaning a lengthy detour for residents needing to reach Le Sueur, Mankato or the Twin Cities.
“It’s a nuisance more than a threat to the city,” Henderson Mayor Keith Swenson said. “It probably adds 30 miles to most people’s commutes, because you have to go way west, or cut through gravel roads that won’t stand up to the traffic anyway.”
Flooding and road closures are familiar to Henderson residents — but Swenson said officials are keeping a close watch on the rainy forecast.
“We’re in a cycle right now, a weather cycle, that — these recurring rains, it’s a new projection every morning when we look at the graphs and say, ‘Oh my God, it’s gonna be another foot higher than they thought it was yesterday,’ ” he said.
Downstream from Henderson, MnDOT said the State Highway 41 bridge across the Minnesota River at Chaska is slated to close at 9 a.m. Thursday as flood waters move along the river.
And in the Twin Cities, parts of Fort Snelling State Park along the Minnesota and Mississippi rivers are already closed due to ongoing high water levels.
Flood warnings remain in effect for the Crow River, which is forecast to reach major flood stage at Mayer and Delano later this week, and moderate flood stage at Rockford.
Public works staff in Delano are preparing for the rising water. The city reported Monday that it has closed storm sewer valves to prevent river water from backing up into the system.
The rising river has prompted officials to close Carver County Highway 123 between Watertown and Mayer.
Flood warnings are also in place for parts of the Cannon, Cottonwood and Redwood rivers.
Tuesday morning severe storms
After strong storms caused damage and widespread power outages across southern Minnesota early Monday, the northern part of the state was hit early Tuesday.
A line of storms prompted severe thunderstorm warnings and produced winds in excess of 65 mph as it barreled through the Red River Valley and eastward across Minnesota.
Utility companies reported scattered power outages affecting more than 2,000 homes and businesses early Tuesday. That number fluctuated through the morning.
More strong storms are possible across the state on Tuesday afternoon, with a threat for large hail, damaging winds and heavy rain.
Find forecast updates on MPR Weather’s Updraft blog.
Future of the floodplain amid climate change
After two years of drought patterns, farmers now face saturated soil and waterside cities are bracing for rivers to breach their banks. Much of Minnesota is in a floodplain, “but everywhere that it rains, it can flood,” said Ceil Strauss, state floodplain manager, during Tuesday’s Morning Edition. “Especially in more recent years, we’re seeing more and more urban flooding and more flooding outside of FEMA-mapped areas.”
In Minnesota, rain events of 6 inches or more are four-times more common since 2000 compared with the previous three decades; events with more than 3 inches of rainfall have gone up 65 percent since the turn of the century, the Department of Natural Resources reports. These massively wet storms are causing more erosion and stream instability, thus leading to more damage to sewers, bridges, roads and other utilities.
As climate changes, so does floodplain management. There haven’t been as many major floods in the news lately because of successful mitigation, according to Matt Bauman, Minnesota Flood Hazard Mitigation Grant Assistance Program manager. Strauss agrees, citing limiting development in higher-risk areas of the state, solid municipal floodplain ordinances and more thoughtful water management.
Out of devastation arose innovation and increased safety. The 1997 spring flooding on the Upper Minnesota and Red rivers caused an estimated $2 billion in damage and economic impact and led to 58 of Minnesota’s 87 counties being declared federal disaster areas. Afterward, the Fargo-Moorhead community began work on a diversion to prevent more catastrophic damage. The project is on track to completion by 2027.
The Red River basin was hit with another round of major flooding in 2009, prompting Moorhead to take action. Since then, and with the help of about $100 million in state grant assistance, the city has bought more than 250 properties and converted them into open public spaces and erected 12 miles of levee and floodwall, the DNR reports.
In the summer of 1978, flash flooding in and around Rochester claimed several lives, set an all-time record high of 23.36 feet for the Zumbro River and put at least a quarter of the city six feet underwater, according to the National Weather Service.
In response, the U.S. Army Corps of Engineers and the Natural Resources Conservation Service built a control system to prevent a 200-year flood event. Strauss said a flood of similar magnitude hit the area in 2019, but the reservoirs did their job, and no lives were lost.
Still, though, Strauss says mitigation and prevention must continue.
“Because of climate change, more of the rain we’re seeing is coming in those intense storms. So the 8, 9, 10-inch storms we’re seeing around the state, we are doing more capturing of that water, trying to do more projects, having our critical facilities be outside the 500-year floodplain, even,” she said. “We’ve done a lot of good work but there’s going to be more to do because we are seeing more of those big flashy storms.”