The upper Mississippi is flooding, but it likely won’t hit those stages around St. Louis
Parts of the Mississippi River north of St. Louis have hit moderate and even major flood stages this year following rapid snowmelt in the Upper Midwest.
But those stages are not as likely around the Gateway City because of the way the river changes near St. Louis.
“The fact that the river is wider there, is used to having more contributions from tributaries. We’re not getting that this year,” said Mike Welvaert, a hydrologist with the National Weather Service. “It’s strictly what’s coming from the Mississippi itself.”
States like Wisconsin, Minnesota and North Dakota had a lot of snowpack that drained into the Mississippi when temperatures jumped after a cooler spring, he said.
The snow melt is essentially over, meaning future risk of flooding will primarily come from any precipitation, Welvaert said.
Many cities in the Upper Midwest have seen the river already reach its crest, as the water moves down through the system.
Closer to St. Louis the Mississippi is forecast to hit moderate flood stage of 22 feet in the Quincy area midweek. It isn’t cause for major concern, said John Simon, the emergency management director for Adams County.
“There’s going to be some roads that start to get flooded,” he said. “No major thoroughfares until we hit about 23 feet. Where we’re at is really in that monitoring phase.”
Simon said some lower-lying park and open land areas will see some flooding too. The county’s actions to respond to flooding mainly center around when the river hits the major flood stage at 26 feet, he added.
Additional rainfall in the coming days and weeks could make the river’s level rise or mean higher levels last longer, Simon said.
“Whether that elongates it or actually makes it rise is yet to be determined,” he said. “Best-case scenario and probably the most probabilistic scenario that we’re looking at right now is, we get around that 22-22.5 feet, and it starts to go back down.”
This year’s flooding is different from near-record levels in 2019 because the high water is primarily in the mainstem of the Mississippi itself, said Welvaert.
“We had all these Iowa tributaries and Northern Illinois tributaries contributing to the flooding,” he said. “Plus there was a pretty significant rain, in fact there were two or three of them.”
Communities along the Mississippi River have also added more flood slack since 2019 and before, said Colin Wellenkamp, executive director of the Mississippi River Cities and Towns Initiative.
“More and more of our cities have been moving folks out of floodplain and giving floodplain back,” he said. “We have more places to move water now that we did before in 2019 and before.”