CLIMATE IMPACTS

Record floods worsened by warming and levees. 'How idiotic'

Is climate change exacerbating record flooding along the Mississippi River that's ravaging parts of Iowa, Illinois and Missouri?

Yes, it is, experts say.

A snow-slogged and rainy springtime in the Midwest has helped drive the river to heights not seen since the Great Flood of 1993. But the exact role that rising temperatures are having on this year's flooding is an open question.

"There's no question in my mind that there's something going on," Gerald Galloway, a civil engineering professor at the University of Maryland's Center for Disaster Resilience and one of the nation's foremost experts on the Mississippi River's hydrology, said in a telephone interview.

"And to those who ask, 'Would this flood have happened with or without climate change?' I say, what difference does it make?" he added. "We know good scientists are telling us that climate change is having an impact, and that's worth taking into account."

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But how much?

Galloway and other experts say the causes of one of the worst floods in a generation will not be fully understood for years. By that time, there will likely have been at least one flood, and maybe more, along the Mississippi that will challenge 1993 or 2019 as the "flood of record."

"It's clear climate change is going to be a huge factor, without a doubt," said John Barry, the journalist and historian who wrote what many consider to be the definitive book on the origins of Mississippi River flooding, "Rising Tide: The Great Mississippi Flood of 1927 and How It Changed America." But, he added, "it remains to be seen whether that will turn out to be the case here," noting that the long history of Mississippi River flooding is shaped by contradictory events.

"These could all be random events piled on top of one another," Barry added. "Long-shot events come in every day."

That doesn't mean climate change should be discounted.

A growing body of scientific evidence, including last year's National Climate Assessment, made clear that "increasing precipitation, especially heavy rain events," across the Midwest "has increased the overall flood risk, causing disruption to transportation and damage to property and infrastructure."

And in large river basins like the Mississippi and Missouri rivers, the report found that floodwaters could inundate more populated areas, "resulting in drinking water contamination, evacuations, damage to buildings, injury, and death."

Four people died in Davenport, Iowa, over the weekend from causes attributed to rising floodwater, according to news accounts, and hundreds were evacuated yesterday after a levee was breached in St. Charles, Mo., west of St. Louis. The river was expected to crest in St. Louis yesterday at 41.2 feet, 11 feet above flood stage and the eighth-highest on record since the 1700s, according to the National Weather Service.

Rising risks from stormwater pollution, property inundation and exposure to life-threatening floods are among the reasons that American Rivers, the national nonprofit group, designated the Upper Mississippi as No. 3 in its 2019 list of most endangered rivers, said Olivia Dorothy, associate director for the organization's Upper Mississippi River Basin campaign.

She watched the river rise to record highs over the weekend from her home in East Moline, Ill., just upstream from Davenport, where river water poured into a section of downtown one week ago after a temporary flood barrier gave way (Climatewire, May 3).

"Preliminary data show that we've surpassed 1993, both in river stage and duration," Dorothy said yesterday. "So this is already a bigger and a longer flood event, and it's definitely not over. We're expecting significantly more rain this week."

Dorothy attributed the high water to "predictable changes in weather patterns" forecast by climate experts, along with a very large snowpack in Minnesota, Wisconsin and northern Iowa that saturated soils in the Upper Midwest when it melted.

"We also have water being moved off the landscape much more quickly through expansion of drainage tiles in Iowa and Minnesota," she said. "All of these things have culminated to create the worst-case flood event that we're seeing on the Upper Mississippi river, and we're going to be seeing this more and more frequently."

That's not to say climate change is the only problem. Other factors are playing a role.

Robert Criss has been studying flood gauge data along the Upper Mississippi for years. The emeritus professor of earth and planetary sciences at Washington University in St. Louis said, "Our flood statistics are way off."

"For us to be setting a record flood again, this is just absurd," Criss said, noting that the Mississippi has hit 40 feet at St. Louis four times since 2013, compared to just seven 40-foot crests between 1785 and 2012.

He said the Mississippi has become "more flashy," essentially rising and falling more erratically, in recent decades, elevating flood risk not only for main-stem river towns like Davenport; Quincy, Ill.; Hannibal, Mo.; and Grafton, Ill., but for communities along the river's tributaries, where backwater flooding has become a growing problem (Climatewire, Aug. 8, 2018).

Criss stopped short of placing too much emphasis on climate change. For him, people are causing a different set of problems: navigation and commercial development up and down the Mississippi.

"This is heavy rain, there's no question about it, and that's going to aggravate the problem," he said. "I'm not saying climate change is immaterial. I'm saying it's not the elephant in the room. The elephant in the room is river constriction. Short of that, we'd have floods, but they wouldn't be record floods."

Criss places much of the responsibility for the more persistent Mississippi flooding at the feet of elected officials and river managers who have allowed the floodplain to be converted for farmland and residential and commercial development. They have done so on the promise that levees and other flood control structures will keep people and property safe, even as the Mississippi has shown time and again it respects no such boundaries.

"Our problem isn't not enough river control. It's too much river control," said Criss, who has frequently clashed with the Army Corps of Engineers over river channelization and flood control measures.

"We've messed with the rivers too much, and we've got to start going backwards and lower some of these levees to allow the river to spread out," Criss added. "A few old river cities, sure, they need their floodwalls. I get that. But trying to wall off both sides of the river for a thousand miles — how idiotic."

Twitter: @dcusickmpls Email: dcusick@eenews.net

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