Heavy Rains, Extreme Flooding Doubled In Midwest Over 50 Years
May 17, 2012

Heavy Rains, Extreme Flooding Doubled In The Midwest Over 50 Years

The Midwest has experienced an increase in extreme rainfall and severe flooding over the last half century and authorities need to take steps now to minimize the impact of these events, two environmental groups said in a report released Wednesday.

The Rocky Mountain Climate Organization (RMCO) and Natural Resources Defense Council (NRDC) in their report -- Doubled Trouble: More Midwestern Extreme Storms -- said severe storms that led to devastating and costly flooding in many Midwestern states are part of a growing trend.

And the trend of more intense rainfall will worsen in the years ahead, said the two-organization report. RMCO and NRDC associated the increasing number of extreme rainstorms -- precipitous events that dump 3 inches or more of rain in a single day -- with a rise in manmade greenhouse gas emissions.

“Global studies already show that human-caused climate change is driving more extreme precipitation, and now we´ve documented how great the increase has been in the Midwest and linked the extreme storms to flooding in the region,” said Stephen Saunders, president of the Rocky Mountain Climate Organization and the report´s lead author.

The RMCO analysis indicates the Midwest (encompassing the states of Illinois, Indiana, Iowa, Michigan, Minnesota, Missouri, Ohio, and Wisconsin) had an increasing number of large storms since 1961. And the largest of the storms, those dumping three inches or more in a day, have increased the most, with annual frequency more than doubling over the last 50 years.

States in the upper Midwest fared worse than their southern counterparts, according to the study. In Wisconsin, the number of severe rain events rose by 203 percent; in Michigan, 180 percent; and in Indiana, 160 percent. Ohio and Iowa saw the smallest percentage increase in severe rainstorms, with 40 percent and 32 percent, respectively.

Overall annual precipitation for the region rose 23 percent in the last 50 years, the study found.

The worst flood year during the period was 2008, followed by 1993. Those two years saw the worst flooding in the Midwest since the 1930s, Saunders told Reuters in an interview by phone.

Extreme flooding devastated the city of Cedar Rapids, Iowa in 2008; and in 2011, the US Army Corps of Engineers blew up Mississippi River levees to protect Cairo, Illinois from a similar fate.

“A threshold may already have been crossed, so that major floods in the Midwest perhaps now should no longer be considered purely natural disasters but instead mixed natural-unnatural disasters. And if (fossil fuel) emissions keep going up, the forecast is for more extreme storms in the region,” Saunders told Reuters by phone.

Climatologist Harry Hillaker responded to the report, agreeing that there is not much doubt that Iowa has had more rain since the 1950s, accompanied by more storms of all types, with the wettest years on record occurring between 2007 and 2010.

But, Hillaker noted, Iowa has had significant precipitation in the past as well. From the late 1840s to the early 1880s, Iowa was “very, very wet, even wetter than what the recent period has been,” he added.

Karen Hobbs, a senior policy analyst for NRDC, said the new report “confirms what most of us in the Midwest have known for a while: Violent storms are becoming more frequent. And the nation´s crumbling water infrastructure just makes the problem worse.”

Saunders pointed to global studies projecting more extreme rainstorms and floods as a result of climate change, which is a product of increased emission of heat-trapping greenhouse gases like carbon dioxide. Carbon dioxide is emitted by natural and human sources, notably the burning of fossil fuels.

James M. Taylor, a senior fellow for environmental policy at The Heartland Institute, said that other factors could also be blamed for the increase in flooding, including development near rivers and streams.

“When you look at national and global precipitation and flooding data, we don´t see anything alarming,” said Taylor, noting skepticism of the report´s claims. The Heartland Institute has challenged previous reports on manmade climate change as well.

WHIO-TV Chief Meteorologist Jamie Simpson said better estimations in recent years of total rainfall could be a factor in the study´s conclusion. “We capture more of the 2 or 3-inch rainfalls. Also we now have the ability to estimate rainfall from radars, which we did not have in the 60s or 70s.”

The report states that local authorities should develop long-term plans that include preventing storm-water runoff and minimizing hard surfaces like blacktop and concrete, preserving existing vegetation, and introducing green space into urban design. Also, in order to protect from more extreme storms, the federal government should enact mandatory limits on fossil fuel emissions.

The report also urges support of the Clean Air Act of the U.S. Environmental Protection Agency.