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This year marks the 10 year
anniversary of the great 1993 flood. Its size and impact was
unprecedented and has been considered the most costly and devastating
flood to ravage the U.S. in modern history. The number of record river
levels, its aerial extent, the number of persons displaced, amount of
crop and property damage and its duration surpassed all earlier U.S.
floods in modern times.
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The Missouri River at Saint
Louis, Missouri |
Uniquely extreme weather and hydrologic
conditions led to the flood of 1993. The stage was set in 1992 with a
wet fall which resulted in above normal soil moisture and reservoir
levels in the Missouri and Upper Mississippi River basins.
These conditions were followed by
persistent weather patterns that produced storms over the same
locations. Their persistent, repetitive nature and aerial extent
throughout the late spring and summer, bombarded the Upper Midwest with
voluminous rainfall amounts. Some areas received more than 4 feet of
rain during the period.
In the St. Louis National Weather
Service (NWS) forecast area encompassing eastern Missouri and southwest
Illinois, 36 forecast points rose above flood stage, and 20 river stage
records were broken. The 1993 flood broke record river levels set during
the 1973 Mississippi and the 1951 Missouri River floods.
In April, the Mississippi River had
crested 6 to 10 feet above flood stage and once again near the same
levels during the month of May. In the beginning of June the rivers
dropped below flood stage and were receding. During the second week of
June, river levels rose to near flood stage before yet again beginning
their slow recession. By the end of June, the Mississippi River was four
feet below flood stage at St. Louis, while many other river locations in
the region were near flood stage. Precipitation for the month averaged
from one inch above normal at Kansas City, to nearly four inches above
normal at Springfield.
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The view at the riverfront |
Starting as early as June 7, reports
of levees being overtopped and levee breaks became common. These
breaches acted to delay the flood crests, temporarily storing excess
water in the adjacent lowlands, but the rain kept falling.
July brought more heavy rain to the
Missouri and upper Mississippi River basins in Missouri, Iowa, Kansas,
Nebraska, North and South Dakota, Illinois and Minnesota. Rainfall
amounts of 5 to 7 inches in 24 hours were common. Precipitation for the
month averaged from one inch above normal at St. Louis and Springfield,
to between six and seven inches above normal at Columbia and Kansas
City, Missouri. The copious rain amounts during July sent record setting
crests down the Mississippi and Missouri Rivers, causing river gages to
malfunction along the way. Both record crests met each other at their
confluence near St. Louis within days of each other.
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Water encroaching on the City
of Alton, Illinois |
The Mississippi River stalled a few
days at the April 1973 record stages, seemingly waiting for the Missouri
River to arrive, before pushing levels upwards again, breaking levees,
driving people and their possessions to higher ground and causing havoc
with anything in its path.
The crests, now combined as one,
moved downstream through St. Louis and Chester on its way to the
confluence with the Ohio River at Cairo, IL. Only minor flooding
occurred below the Ohio due to the drought the eastern U.S. was facing
the same time.
Major sandbagging activities were
underway on the lower Missouri River, the River Des Perre in St. Louis,
the Mississippi River south of St. Louis and on many other tributaries
across Missouri and Illinois. Some of these efforts were successful
while others were not as the river continued to spawn destruction.
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Volunteers sandbagging to
protect life and property |
Over 1,000 flood warnings and
statements, five times the normal, were issued to notify the public and
need-to-know officials of river levels. In places like St. Louis
Missouri, river levels were nearly 20 feet above flood stage and had
never been this high in its 150 year history. The 52 foot St. Louis
Flood wall, built to handle the volume of the 1844 flood, was able to
keep the 1993 flood out with just over two feet to spare.
On August 1, levee breaks near
Columbia, Illinois flooded 47,000 acres of land, inundating the towns of
Valmeyer and Fults, Illinois. The released water continued to flow
parallel to the river, approaching the levees protecting historic
Prairie du Rocher and Fort de Chartres, Illinois. On August 3, the Corps
of Engineers made the tough decision to break through the stronger
Mississippi River levee to allow the water back into the river. The
innovative plan worked and the historic areas were saved.
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Eads Bridge at St. Louis,
Missouri |
On the Missouri River it was
estimated that nearly all of the 700 privately built agricultural levees
were overtopped or destroyed. Navigation on the Mississippi and Missouri
River had been closed since early July resulting in a loss of $2 million
(1993) dollars per day in commerce.
The Mississippi River at St. Louis
crested at 49.6 feet on August 1, nearly 20 feet above flood stage and
had a peak flow rate of 1.08 Million cubic feet per second. At this
rate, a bowl the size of Busch Stadium would be filled to the brim in 69
seconds.
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Head for higher ground |
Some locations on the Mississippi
River were in flood for almost 200 days while locations on the Missouri
neared 100 days of flooding. On the Mississippi, Grafton, Ill., recorded
flooding for 195 days, Clarksville, Mo, for 187 days, Winfield, Mo., for
183 days, Hannibal, Mo., for 174 days, and Quincy, Ill., for 152 days.
The Missouri River was above flood stage for 62 days in Jefferson City,
Mo., 77 days at Hermann, Mo.; and for 94 days at St. Charles in the St.
Louis metropolitan area. On October 7, 103 days after it began, the
Mississippi River at St. Louis finally dropped below flood stage.
In the 10 years since 1993, the NWS
has made many improvements to their river forecasting and information
delivery systems. Improved science, computing power, model calibration,
higher density, more frequent and timely river and rainfall data, along
with the Advanced Hydrologic Prediction Service (AHPS) have increased
our timeliness and service to the public. AHPS is now available on our
website at http://www.crh.noaa.gov/lsx. By clicking 'River Info/AHPS' in the
left Margin under 'Hydrology', it is quick and easy to assess the
current hydrologic situation, accessing current and forecast hydrologic
conditions in addition to historic flood and low water information.
For more information visit our
National
and Regional
Flood accounts
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