Researchers say modern technology has contributed to making flooding along the Mississippi River worse.
Research from a group of geoscientist headed by Samuel Munoz, an assistant professor of marine and environmental sciences at Northeastern University, has shown that the river’s levees and floodways have contributed to flooding along the waterway rather than protecting nearby land and people. The study, published in the science magazine Nature, shows that the construction along the river's banks has led to an increased in the degree of flooding by 20 percent during the past 100 years.
"The obvious culprit is that we have really modified the river itself," Munoz said. His team of eight researchers found that climate change and an increase in rainfall over the recent past hasn’t been enough to account for the uptick in massive floods along this major U.S. waterway.
Using tree rings and sediment from the river’s oxbow lakes - lakes that form off of large rivers, which can receive flood runoff from the river - the researchers created a 500-year record of Mississippi River floods.
The 1930s engineering projects profoundly altered the river’s shape and sediment content, the group of researchers found. "The early 20th century got a lot of flooding," but climate patterns can explain only 25 percent of the increase in flood magnitude over the past century, Munoz says, the other 75 percent were from the levees and floodways, he concludes.
The researchers also accounted for the major U.S. weather patterns - El Niño-Southern Oscillation and the Atlantic Multidecadal Oscillation, and considered that amount of rainfall in the past century could be affected by warmer weather along the Mississippi River.
The 500-year flood record "gives a long-term perspective on the Mississippi, which you really need to understand a river of its size and majesty. … This approach can help take the pulse of a river and determine how unprecedented, such changes might be," Muñoz added.