Case Study: The 1993 Upper Mississippi River Basin Floods

Linn Grove,
Iowa. Aug
“The Great Flood of 1993”
Adam Baumeister
ESS 315
Watershed for the Mississippi River
•Compare the average rainfall for
the Mississippi basin (above), with
the averaged precipitation for the
same region From April to
September (right).
•If you add “giant drainage basin”
to “really big river” and multiply it
by “four times as much rain as
usual, you get…
Veenker Golf Course,
Ames, IA, 1993
…Practicing your rowing on a golf course.
Some important facts:
•The vast majority of the Mississippi drainage basin is one big open topped
•Fall of 1992 had dramatically high rainfall throughout the northern Midwest,
leaving the region fairly well saturated when winter set in, and that winter saw
heavy snowfall as well.
•Spring of 1993 started off with heavy rainfall as the snow was melting, raising
concerns of flooding even as early as the first week of April that year.
•A “Flood” as defined by the USGS is “an overflow or inundation that comes from
a river or other body of water and causes or threatens damage. Any relatively
high streamflow overtopping the natural or artificial banks in any reach of a
stream. “
Water Volumes:
• Average Flow for the Mississippi is
450,000 cu ft/s (12,743 m3/s)
• For the Flood of 1993, it peaked at
541,000 ft³/s (15,300 m³/s), and broke 92
different “Crest Records” along the rivers.
St. Louis saw a maximum flood height of
49.47 feet on August 1st.
Damage Report:
Darker shades = Greater $$$
Total Damages:
• Some locations on the Mississippi River flooded
for almost 200 days while locations on the
Missouri neared 100 days of flooding.
• Approximately 10,000 homes were destroyed as
a result of the flooding.
• 15 million acres (60,000 km²) of farmland was
• The floods cost thirty two lives officially;
however, a more likely target is suspected to be
around fifty people.
• An estimated total 20 billion dollars in damages
across all areas.
Some more facts:
• 400,000 square miles of land in the Missouri and Mississippi basins
was officially declared “flooded”.
• Floodwater removed more than 600 billion tons of topsoil from the
heavily agriculturally developed Midwest, and deposited untold
amounts of silt and sand in their place.
• Barge traffic on both rivers was completely stopped for two months.
• Numerous water and sewage treatment plants across the affected
area were flooded and deactivated or destroyed. The water
treatment facility in Des Moines, Iowa, for instance, has its levies
fail, and caused a complete shutdown of service of fresh water for
the entire downtown and southern end of the city of ~350,000
people for 18 days, and running water of any sort for 11 days.