Villarini, G., Smith, J.A., Baeck, M.L. and Krajewski, W.F. 2011. Examining flood frequency distributions in the Midwest U.S. Journal of the American Water Resources Association 47: 447-463.
The authors write that the Upper Midwest United States -- consisting of North Dakota, South Dakota, Nebraska, Kansas, Minnesota, Iowa, Missouri, Wisconsin and Illinois -- "has been plagued by flooding over the past 100 years," and they say that "these events are responsible for numerous fatalities and large economic damage (e.g., Changnon, 1997, 1999; Pielke and Downton, 2000; Otto, 2009), in particular over the last two decades, with the 1993 and 2008 floods causing economic losses in excess of one billion dollars."
What was done
In an effort to determine if Upper Midwest U.S. floods have been increasing in recent years, as climate alarmists claim should be happening all around the world in response to global warming, Villarini et al. "analyzed the annual maximum instantaneous flood peak distributions for 196 U.S. Geological Survey streamflow stations with a record of at least 75 years over the Midwest U.S."
What was learned
The four U.S. researchers report that in the vast majority of cases where streamflow changes were observed, they were "associated with change-points (both in mean and variance) rather than monotonic trends," and they indicate that "these non-stationarities are often associated with anthropogenic effects." But rather than increases in anthropogenic CO2 emissions, they cite such things as "changes in land use/land cover, changes in agricultural practice, and construction of dams and reservoirs."
What it means
Based on their findings, and, as they note, "in agreement with previous studies (Olsen et al., 1999; Villarini et al., 2009)," they conclude that "there is little indication that anthropogenic climate change has significantly affected the flood frequency distribution for the Midwest U.S." And as they make doubly clear in the abstract of their paper, they say that "trend analyses do not suggest an increase in the flood peak distribution due to anthropogenic climate change."
Changnon, S.A. 1997. Impacts and responses to the storm. In: Changnon, D. (Ed.). The Record Rainstorm on July 17-18, 1996, in Northern Illinois. Illinois State Water Survey, Champaign, Illinois, United States, pp. 121-140.
Changnon, S.A. 1999. Record flood-producing rainstorms of 17-18 July 1996 in the Chicago metropolitan area. Part III: Impact and responses to the flash flooding. Journal of Applied Meteorology 38: 273-280.
Olsen, J.R., Stedinger, J.R., Matalas, N.C. and Stakhiv, E.Z. 1999. Climate variability and flood frequency estimation for the Upper Mississippi and Lower Missouri. Journal of the American Water Resources Association 35: 1509-1523.
Otto, D. 2009. Economic losses from the floods? In: Mutel, C.F. (Ed.). A Watershed Year: Anatomy of the Iowa Floods of 2008. University of Iowa Press, Iowa City, Iowa, United States, pp. 139-146.
Pielke, R.A. and Downton, M.W. 2000. Precipitation and damaging floods: Trends in the United States, 1932-97. Journal of Climate 13: 3625-3637.
Villarini, G., Serinaldi, F., Smith, J.A. and Krajewski, W.F. 2009. On the stationarity of annual flood peaks in the continental United States during the 20th century. Water Resources Research 45: 10.1029/2008WR007645.Reviewed 3 August 2011