The frequency and intensity of flooding in the Central United States is trending upward, according to a 2015 study published in Nature Climate Change.
The study, called “The Changing Nature of Flooding across the Central United States,” states that the “frequency of flooding events has been increasing while the magnitude of historic events has been decreasing, the largest proportion of floods occurred in the spring and summer time with spring being the higher possibility for flooding than the summer, and trends of rising temperature yield an increase in available energy for snow melting and the observed trends in increasing flood frequency can be related to both increasing temperature and rainfall.”
The researchers in the study Iman Mallakpour and Gabriele Villarini of the University of Iowa examined data from 774 stream gauges between the years 1962 and 2011. The 14 states that were examined were Illinois, Indiana, Iowa, Kansas, Kentucky, Michigan, Minnesota, Missouri, Nebraska, North Dakota, South Dakota, Ohio and West Virginia.
Of those 14 states Illinois, Indiana, West Virginia, Kentucky and Ohio make up the Ohio Valley – the area that surrounds the Ohio River, the largest tributary of the Mississippi River. Jim Belles, meteorologist in charge at the National Weather Service Forecast Office in Memphis, said that a majority of the water that the Memphis area receives comes from the Ohio Valley and down the Mississippi River.
“We really scrutinize this area due to the amount of water that travels down to the Mississippi River,” Belles said. “While the snow in the Ohio Valley is not as excessive as the Northeast, the melted snow travels down the Mississippi River but it does not drain the Mississippi River Basin.”
Some events, such as global warming, can be attributed to this increasing trend of flooding in the central United States. Belles said that climate change is something that has always been throughout Earth’s history.
“Flooding all depends on the location of people,” Belles said. “We have always had floods so you have to be cautious about blaming climate change. Now if the frequency of these events increases, then you have to start researching and determine what is the reason behind these events.”
Belles agrees that spring and summer are the most common seasons for flooding – especially springtime – due to the overlapping of seasons which creates these snowmelts.
“The land doesn’t have as much capacity to receive heavy rainfall,” Belles said. “The ground may already be saturated due to the temperature and snow melting. Flooding is more in the springtime because with things such as vegetation emerging, the amount of infiltration increases.”
Belles said that torrential rainfall can also be attributed to flash floods with the high amounts of rain that occur during these events cause brief floods to happen in the area.
The National Weather Service Weather Forecast Office in Memphis also tries to help prevent casualties in times of severe flooding.
“There is a phrase that we have for preparedness during these events,” Belles said. “We call it ‘Turn Around, Don’t Drown.’ Most deaths during floods occur in vehicles; you’ll be surprised how many people perish inside their vehicles.”
