Record Floods Could "Test the Limits" of Midwest Defenses
Low-lying communities from Minnesota to Missouri are bracing for what could be the Mississippi Basin’s worst flooding since 1993 as temperatures rise and rainstorms continue to track over areas with deep winter snowpack.
The weekend brought some of the worst flooding in decades to towns along the Missouri River and its tributaries in Nebraska and Iowa, killing two and forcing evacuations from communities south of Omaha, Neb.
By yesterday, the focus was shifting south and east toward Kansas City and then to the confluence of the Missouri and Mississippi rivers north of St. Louis.
“We’re expecting some considerable impacts over the next few weeks,” said Colin Wellenkamp, executive director of the Mississippi River Cities and Towns Initiative based in St. Louis. “This is going to test the limits of some of our member cities.”
Col. Doug Guttormsen, commander of the Army Corps of Engineers Kansas City District, cautioned residents along the lower Missouri to be “very mindful of high water” and prepare to quickly evacuate if ordered by state and local emergency managers.
The Army Corps was also working with local levee districts on sandbagging and other temporary flood control measures along the river as far east as Alton, Ill. Officials reported at least nine levee breaches along the Missouri south of the Platte River and four breaches of nonfederal levees closer to Kansas City.
The National Weather Service said it expected the Missouri to crest later this week in St. Joseph, Mo., at the third-highest level ever recorded.
Hundreds of homes were flooded in Nebraska and Iowa as of yesterday afternoon, and many thousands of acres of corn and soybean fields are inundated with water, according to local media reports.
Much of the weekend flooding was attributed to the recent “bomb cyclone” that brought late-season snow, rain and hurricane-force winds to the Great Plains and Midwest. But weather experts say a second wave could come this week as 50-plus-degree temperatures extend into Minnesota and Wisconsin, melting what remains of the region’s record February snowfall.
NOAA reported earlier this month that the winter of 2018-19 was the wettest on record, and it was accompanied by marked swings in temperature.
Spring thaw and snowmelt are routine in the northern half of the country. But experts say the current flood crisis is exacerbated by several conditions occurring at once. Heavy rain is falling onto a dense layer of snow atop frozen ground. With little or no soil absorption, the water is forced to run off into streams and rivers.
Scientists say such events may become a greater concern with climate change, as rising average temperatures mean precipitation may fall more variably—as both rain or snow—over the northern half of the country. Climate projections also suggest that heavy precipitation events will become more severe in many places.
The 2014 installment of the National Climate Assessment cites the northern Great Plains as one region expected to see an increase in winter precipitation in the future. It notes that “increased snowfall, rapid spring warming, and intense rainfall can combine to produce devastating floods.”
Some scientists have suggested that climate change may affect major atmospheric circulation systems in ways that could affect weather patterns and severity. For example, some believe the jet stream is becoming prone to wider up-and-down fluctuations in its flow over time—and that these atmospheric changes may be linked to rapid warming in the Arctic.
A wavier jet stream could also cause an increase in severe weather events, like the bomb cyclone, or cause severe weather to linger in one place for longer periods, potentially causing more damage. Such ideas, though, remain a point of debate among climate scientists.
What is not debatable is the amount of water flowing south from the nation’s snow-covered regions into the middle of the country, where the Missouri, Ohio and other smaller river basins meet an already swollen Mississippi River.
While dozens of cities, large and small, face higher flood risk this spring along the Mississippi, Wellenkamp said the basin’s mayors have worked individually and collectively to better prepare for floods and to adapt to climate change risks. For instance, Dubuque, Iowa, and Grafton, Ill., have taken steps to restore large wetland areas in their cities’ floodplains to allow the river more room to swell during flood tides.
Mayors have also improved flood response coordination so that upstream communities don’t worsen conditions for cities downstream.
“Mayors up north are not dumping snow into the river the way they used to,” Wellenkamp said. “They are placing it outside the watershed.”
River communities have also become more engaged in relocating residents out of floodplains where they face much higher risks to life and property.
“After 1993, we started moving people out, and we’re still doing that today,” Wellenkamp said. “It’s very expensive, but the cost of rebuilding flooded homes is much higher.”
Reprinted from Climatewire with permission from E&E News. E&E provides daily coverage of essential energy and environmental news at www.eenews.net.