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Midwest flooding more frequent

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Originally appeared in IowaNow, 2015.02.09. Story by GARY GALLUZZO.
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Iowa River flooding, June 2014.

The U.S. Midwest and surrounding states have endured increasingly more frequent flood episodes over the past half-century, according to a study from the University of Iowa.

The UI researchers based their findings on daily records collected by the U.S. Geological Survey at 774 stream gauges in 14 states from 1962-2011, a data-collection period in common for all the stations.

They found that 264 (34 percent) of the stations had an increase in frequency in the number of flood events, while only 66 stations (nine percent) showed a decrease.

Gabriele Villarini

Gabriele Villarini

“It’s not that big floods are getting bigger, but that we have been experiencing a larger number of big floods,” says Gabriele Villarini, UI assistant professor of civil and environmental engineering and corresponding author on the paper, published Feb. 9 in the advance online edition of the journal Nature Climate Change.

The findings likely come as no surprise to millions of people in the Midwest and bordering states. During the past several decades, large floods have plagued the region in 1993, 2008, 2011, 2013 and again in 2014. The floods have caused agricultural and economic losses in the billions of dollars, displaced people and led to loss of life.

Iman Mallakpour

Iman Mallakpour

“There is a pattern with increasing frequency of flood events from North Dakota south to Iowa and Missouri and east into Illinois, Indiana and Ohio,” says Iman Mallakpour, UI graduate student in civil and environmental engineering and lead author on the paper.

“We related this increasing number of big floods to changes in rainfall and temperature. There was an overall good match between the areas with increasing frequency of flood events and areas experiencing increasing frequency of heavy rainfall events,” adds Villarini, who is also assistant research engineer at IIHR – Hydroscience & Engineering.

He notes that seasonal analysis revealed that most of the flood peaks in the upper Midwest occur in the spring and stem primarily from snow melt, rain falling on frozen ground and rain-on-snow events. Interestingly, spring—in addition to being a season with increasing frequency of heavy rainfall—also has the strongest increase in temperature over most of the northern part of the region studied, he says.

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.

Villarini says the current study did not attempt to link the increase in the number of episodes to climate change.

“What causes the observed changes in precipitation and temperature is not something we have addressed because of the difficulties in doing so just based on observational records,” Villarini says.

The study region included: Iowa, Illinois, Indiana, Wisconsin, Ohio, Michigan, Minnesota, Kansas, Nebraska, Missouri, West Virginia, Kentucky, North Dakota and South Dakota.

The methodology used in the study involved establishing a threshold level of two flood events per year, on average, for each of the 774 stream gauges in the study, so as to focus on the larger flood events. In order to avoid counting the same event twice, the researchers allowed for the recording of only one event within a 15-day period.

The paper titled, “The Changing Nature of Flooding across the Central United States,” can be found on Nature’s website.

The U.S. Army Corps of Engineers Institute for Water Resources, the Iowa Flood Center and IIHR-Hydroscience & Engineering funded the work. Funding also came from the National Science Foundation, under NSF CAREER Grant #AGS-1349827.

Current Flood Conditions

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If you have questions related to current flood conditions, please contact the Iowa Flood Center at 319-384-1729.

The Iowa Flood Center (IFC) at the University of Iowa has an online tool, the Iowa Flood Information System (IFIS), allowing all Iowans to access the latest community-based flood conditions, including current stream and river levels at nearly 300 US Geological Survey and IFC gauges across the state.

To access IFIS, go to http://ifis.iowafloodcenter.org.  From this page, users can launch IFIS.

IFIS, developed by the Iowa Flood Center, is a user-friendly online application based on a Google Maps-interface.  IFIS displays up-to-the-minute community-specific information on rainfall, stream levels, and more, including:

  • Real-time stream levels at nearly 300 locations in Iowa;
  • Current flood warnings and stream forecasts;
  • Real-time rainfall maps displaying current conditions and past rainfall accumulation; and
  • Flood inundation maps for select communities, including Ames, Cedar Rapids, Charles City, Des Moines, Iowa City, Mason City, Ottumwa, Spencer, and Waterloo/Cedar Falls.
IFIS_inundationmap

One tool in IFIS allows users to view possible inundation in some communities.

IFIS_rain&conditions

Another tool allows users to view daily rainfall alongside current river conditions.

The Iowa Flood Center is part of IIHR—Hydroscience & Engineering, a research institute based at the University of Iowa’s College of Engineering. The IFC was established in 2009 to provide accurate, state-of-the-science-based information to help Iowans better understand their flood risks. It is the nation’s first academic center devoted solely to the study of floods.

CONTACT:
Sara Steussy, Iowa Flood Center, 319-384-1729, sara-steussy@uiowa.edu

Flood of 2013 in Boulder, Colorado

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Guest editorial by Vijay K. Gupta, University of Colorado, Boulder

Vijay K. Gupta

We experienced the evolution of an extreme rainfall event and the flood that followed during the week of September, 11-18, 2013. The devastation was widespread in the Front Range, Colorado, but Boulder got the brunt of it. It was a rare opportunity to experience first hand an extreme geophysical event.

Prof. P. E. O’Connell, University of Newcastle, UK, was invited as the Arthur Boase Lecturer to the University of Colorado in 2008. During his visit, he presented me with a poster of Boulder’s great flood of 1894. A historical description of the flood is given here. Scenes of the flood and its aftermath were captured by two Boulder photographers, Lawrence Bass and Joe Sturtevant. My poster is a photo by Bass. It appears from a visual inspection that the 2013 flood is comparable in its severity to the 1894 great flood.

Floods are among the extreme geophysical events. An AGU Chapman conference on “Complexity and Extreme Events in Geosciences” was held in India in February, 2010. The newly developing nonlinear geophysical science is providing an interdisciplinary forum for different sections of AGU to exchange common ideas. This perspective is explained in an overview article coauthored by 12 colleagues from different AGU sections, and published in an AGU monograph on Complexity and Extreme Events in Geosciences, 2012. My talk at the conference was devoted to a nonlinear geophysical theory of floods (Gupta et al., Geophys. Res. Lett., 37, L11402, doi:10.1029/2009GL041540, 2010.), but our paper in the AGU monograph addresses a long-standing open problem on droughts.

What caused such an extreme rainfall event that led to the flood? In a new article published in New Scientist quotes an atmospheric scientist from the National Center for Atmospheric Research in Boulder saying, ”[…] that huge volume was due in part to a lingering heat wave that for months blocked tropical moisture from the Gulf of Mexico from reaching the Rocky Mountains. When that heat wave began to move east last week, weak winds allowed the growing storm system to sit above the Colorado peaks for days. Once that deluge hit the ground, more trouble awaited. Because of Colorado’s mountainous terrain, the region is flood-prone anyway but recent wildfires exacerbated things near Boulder and Fort Collins, two areas hardest hit by floodwaters. The fires had cleared land of vegetation that would normally absorb rainwater.”

The USGS designated it as a 100-year flood. It means that a flood of this magnitude has a chance of 1/100 to occur in any year. Standard calculations show that a 100-year flood has about 2/3 probability to occur at least once in 100 years. How does USGS assign such probabilities is an important question because data on extreme events are few and far between? The science of floods remains a challenging and a fascinating topic despite many advances that have taken place in the last three decades. I hope that new graduate students would give it a serious consideration in selecting their dissertation research topic.

Vijay K. Gupta is a professor of Civil, Environmental and Architectural Engineering at the University of Colorado in Boulder. He developed the theoretical foundation of the flood forecasting models that the Iowa Flood Center is pursuing in order to provide alerts to over 1,000 communities in Iowa via the Iowa Flood Information System. 

Support Colorado Disaster Relief Efforts

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Sen. Rob Hogg

Sen. Rob Hogg

“Based on our flood experiences, we know that outside charitable help has a critical, positive role to play in addressing flood disasters. Flood victims need federal, state, and local help, too, but they also need charitable assistance. Please give generously to disaster relief for Colorado. Contributions can be sent to the American Red Cross, 6300 Rockwell Drive NE, Cedar Rapids, IA 52402, and other relief agencies.”  – Sen. Rob Hogg, Cedar Rapids

Last week, devastating floods ravaged Colorado’s Front Range, especially the communities of Boulder, Fort Collins, and those in the surrounding counties and rural communities. People lost lives, families lost homes, and many people are still unaccounted for. As the people of Iowa remember the numerous floods that affected us in the past five years, the Iowa Flood Center joins Senator Rob Hogg in his call for donations for the Colorado floods.

Boulder has a special place in the short history of the Iowa Flood Center. It was Vijay K. Gupta, professor at the University of Colorado in Boulder, who developed the theoretical foundation of the flood forecasting models that we are pursuing in order to provide alerts to over 1000 communities in Iowa via our Iowa Flood Information System. His former student is Ricardo Mantilla, now a Research Engineer at the IFC and the main architect of the state-wide modeling system we use in our studies.

And more recently, during the field campaign we hosted, the Iowa Flood Studies, or IFloodS, many participating scientists were from Colorado State University in Fort Collins. These experts on radar and satellite remote sensing of precipitation are helping us improve our state-wide maps of rainfall. Many former students of IIHR—Hydroscience & Engineering reside in Boulder, Fort Collins, Denver and the nearby communities. All these ties provide additional significance to the recent events in Colorado.

krajewski

Witold Krajewski

The Iowa Flood Center was an outcome of the 2008 flood in eastern Iowa, and we work tirelessly to help Iowans be better prepared for future weather events. While it is too soon to tell what approach the state of Colorado will take to rebuilding in the wake of these extraordinary floods, we stand ready to share our expertise. But for now, we can all help by donating.

The Colorado Division of Homeland Security and Emergency Management has partnered with the Colorado Voluntary Organizations Active in Disaster to provide a website to help those affected by the flooding. To make a financial contribution or learn more, visit helpcoloradonow.com.

Witold F. Krajewski
Director, Iowa Flood Center