For the Midwest, Epic Flooding Is the Face of Climate Change (abridged)
By: MEGAN MOLTENI, 05.24.2019

Source: Wired.com

Scientists say it’s too early to tell to what degree this particularly relentless spring storm season is the result of human-induced climate change. But they agree that rising temperatures allow the atmosphere to hold more moisture—about 7 percent more for every 1 degree rise in Celsius—which produces more precipitation and has been fueling a pattern of more extreme weather events across the US. And perhaps more than any other part of the country, the Midwest has had its capacity to store excess water crippled by human developments like paved or concrete surfaces.

In 2015, researchers at the University of Iowa studied historical records of peak discharges from more than 700 stream gauge stations across the Midwest. Their analysis, reported in Nature, found that between 1962 and 2011, the magnitude of flood events hadn’t changed much. At a third of the locations, however, the number of floods was trending upward significantly.

More recent work, published in February by scientists at the University of Notre Dame, shows that floods aren't just getting more frequent—they'll also get more powerful in the future. Using a statistical method to blend data from global climate models with local information, the researchers predicted that the severity of extreme hydrologic events, so-called 100-year floods, hitting 20 watersheds in the Midwest and Great Lakes region will increase by as much as 30 percent by the end of the century. The approach, called “Hybrid Delta downscaling,” has been used to look at hydrological dynamics in other parts of the country before, but it was never applied to the Midwest. “What we’re seeing is that the past really is not a good predictor of the future,” says the study’s lead author, Kyuhyun Byun. “Especially when it comes to extreme weather events.”

In Byun’s case, the evidence is as much in his computer simulations as it is in his own waterlogged backyard. In South Bend, Indiana, where Notre Dame is located, the city is still recovering from back-to-back biblical deluges—a 500-year flood last spring preceded by a 1,000-year flood in 2016 that broke all historical records. 

Besides all the damage to homes, businesses, and municipal infrastructure, increasingly frequent flooding events in the Midwest would have a huge impact on the nation’s ability to produce food. Wet fields make it difficult for farmers to operate their large, heavy planting machinery without getting stuck. And seedlings struggle to develop root systems when there’s too much moisture in the ground.