Jefferson County - East-West Gateway Coordinating Council

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Statement of Probable Future Severity
Jefferson County – Section 2
According to SEMA’s Severity Ratings Table, the 1993 floods would qualify as critical.
During the 1993 floods, some facilities were closed for more than 24 hours. Other flood
events had minimal impact on quality of life, no critical facilities or services were shut down
for more than 24 hours, and property damage for the county was about 11%. Therefore,
the probable severity of future floods could range from critical in the floodplain areas to
negligible in the areas outside of the floodplains.
Statement of Probable Risk
Flooding in Jefferson County is likely to occur in the future. Jefferson County faces two
major factors for flooding. First, the land that forms Jefferson County is included the area
that drains to the Mississippi and Meramec River. Secondly, according to the FIRM, 11% of
the land for the Jefferson County lies within the 100-year floodplain. The majority of that
land lies adjacent to the Mississippi River levees and the Meramec River. The Mississippi
River has experienced 14 major flood events since 1785. The Meramec River has
experienced 15 flood events in the last 22 years.
Statement of Next Disaster’s Likely Adverse Impact on the Community
The next flood to invade Jefferson County would follow the pattern of the 1993 floods.
However, post-1993 mitigation measures already have been tested in the 1995 and 2001
flooding along the Mississippi and Meramec River. Despite high river levels, damages were
relatively minimal due to relocation of many homes and businesses. Adverse impacts of
future Mississippi and Meramec River floods are discussed below.
Without Mitigation Measures:
Life: Limited
Property: Limited
Emotional: Limited
Financial: Limited
Comments: The above impacts assume conditions at the time of the 1993 floods over
the entire county. Impacts within the floodplain would be catastrophic; impacts outside of
the floodplain would be negligible.
With Mitigation Measures:
Life: Negligible
Property: Negligible
Emotional: Negligible
Financial: Negligible
Comments: Mitigation measures have already begun in the wake of the 1990s floods.
Further mitigation measures should be directed at improving land use practices and
redesigning vulnerable highways.