Study finds that flood patterns are changing across the U.S.


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The threat of moderate flooding is generally increasing in the northern U.S. and decreasing in the southern U.S. (American Geophysical Union.)
Jake Slobe | May 3, 2017

The risk of flooding is changing by region throughout the United States and two of the reasons could be shifting rainfall patterns and changes in groundwater.

University of Iowa engineers, in a new study, have determined that the threat of flooding is growing in the northern half of the U.S. while declining in the southern half. The American Southwest and West are experiencing decreasing flood risk.

UI engineers Gabriele Villarini and Louise Slater compiled water-height information from 2,042 stream gauges operated by the U.S. Geological Survey. They then compared the data to satellite information gathered over more than a dozen years by NASA’s Gravity Recovery and Climate Experiment mission showing the amount of water stored in the ground.

The study found that northern sections of the country have an increased amount of water stored in the ground and are at increased risk for minor and moderate flooding. Meanwhile, flood risk is decreasing in the southern portions of the U.S., where stored water has declined.

Why some sections of the nation are getting more, or less, rainfall is not entirely clear. The researchers say one cause could be the redistribution of rains as the regional climate changes.

The researchers hope their findings can change how flood patterns are discussed. In the past, flood risk trends have typically been discussed using stream flow, or the amount of water flowing per unit time. The UI study views flood risk through the lens of how it may affect people and property and aligns the results with National Weather Service terminology understood by the general public.

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