Minnesota Water Resources Conference - Water Resources Center ...

Plenary Session 8:10–9:30
The SE Minnesota Floods of August 2007: In Historical and Future Context
Mark Seeley, University of Minnesota Extension Climatologist, University of Minnesota, mseeley@umn.edu
BOOK OF ABSTRACTS
Wednesday, Tuesday, October 24 28 23
The severe thunderstorms of August 18–20, 2007, produced unprecedented amounts of rainfall in some
southeastern Minnesota counties. Observers in Fillmore, Winona, and Houston Counties reported 36 hour
rainfall amounts of 14 inches or greater. For historical context, the observer at Hokah (Houston County)
reported all-time state records for 24-hour rainfall (15.10 inches), storm total rainfall (16.27 inches), and
monthly total rainfall (23.86 inches). The resulting flash floods on the Root River and Whitewater River in SE
Minnesota were fast, fierce, and highly destructive. The gage at Houston along the Root River registered the
highest flash flood crest on record there, 18.15 feet ( flood stage is 15 ft). Historically, this was only exceeded
by the destructive spring snowmelt flood crest of 1965 when a crest of 18.32 feet was measured on March 2nd.
Upstream from Houston, the town of Rushford was almost wiped out. Additionally, a flood crest of 19.24 feet,
highest of record was recorded on the Whitewater River at the state park in northwestern Winona County.
This caused severe damage to the popular state park. For future context, it is important to understand that
the Minnesota climate is changing and producing amplified variation in precipitation. In addition there is a
problematic character change in precipitation that manifests itself as a higher contribution from thunderstorm
rainfall to the annual hydrologic cycle. These changes in climatic attributes and their implications are deserving
of widespread community discussion as adaptation is required to sustain economic stability and protect our
land and water resources from dramatic degradation.
(More on Minnesota’s weather history can be found in the new book by Mark Seeley, Minnesota Weather
Almanac, available at all bookstores or through the Minnesota Historical Society Press.)
Minnesota Water Resources Conference, October 27–28, 2008 58