The frequency of flooding in the Midwest has increased in the last five decades, researchers at the University of Iowa report based on their analysis of stream gauge stations across the region.
Gabriele Villarini, an assistant professor of civil and environmental engineering at UI, who is also the corresponding author of the research, explained that their research findings were based on the daily analysis of records put together by the U.S. Geological Survey at more than 770 stream gauges located in 14 different states from 1962 to 2011.
The researchers reveal that 34 percent, or 264, stations witnessed an increased flood frequency in the last 50 years. Only 9 percent, or 66, of these stations experienced a decrease in floods.
Villarini explains that the larger floods are not getting larger; however, the occurrences of large floods have increased in the past few decades. Villarini also suggests that the findings may not come as surprise to many people living in the Midwest or surrounding states as large floods afflicted the region in 1993, 2008, 2011, 2013 and also in 2014.
The floods cause large-scale economic and agricultural losses but at the same time can also lead to loss of human and cattle life in the region. The study involved the states of Illinois, Indiana, Iowa, Kansas, Kentucky, Michigan, Minnesota, Missouri, Nebraska, North Dakota, Ohio, South Dakota, West Virginia and Wisconsin.
The study involved linking the number and frequency of large floods to the changes in temperature and rainfall. The researchers suggest they found evidence that areas that experienced high rainfall levels also witnessed an increasing number of big floods. The study also found that the highest number of floods in the upper Midwest occur during spring. Melting snow and rain that falls on the frozen grounds are the key factors that result in floods.
"The findings jibe well with current thinking among climate scientists about how the hydrological cycle is being affected by global warming. In general, as the atmosphere becomes warmer, it can hold more moisture. One consequence of higher water vapor concentrations is more frequent, intense precipitation," per the press release of the study.
Because a warmer atmosphere holds more moisture, as global temperatures rise a pronounced increase in intense rainfall events is included in future climate models. That makes it important to look at whether the magnitude and frequency of flood events is remaining constant or has been changing over recent decades, researchers noted, giving rise to the 50-year survey of flood data.
The study has been published in the journal Nature Climate Change.