Jefferson County - East-West Gateway Coordinating Council

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2003 Statistics:
Number of Missouri state-regulated dams: 638
Number of Missouri dams in National Inventory of Dams: 4,096
Characteristics
Jefferson County – Section 2
The characteristics of a dam failure, based on the International Commission of Large Dams
(ICOLD) include following the three major categories of dam failure: (1) overtopping by
flood; (2) foundation defects; and (3) piping. For earthen dams, the major reason for
failure is piping or seepage. For concrete dams, the major reasons for failure are associated
with foundations. Overtopping has been a significant cause of dam failure primarily in
cases where there was an inadequate spillway. Dam failures are most likely to happen for
one of five reasons:
• Overtopping caused by water spilling over the top of a dam
• Structural failure of materials used in dam construction
• Cracking caused by movements like the natural settling of a dam
• Inadequate maintenance and upkeep
• Piping—when seepage through a dam is not properly filtered and soil particles
continue to progress and form sink holes in the dam
Likely Locations
The National Inventory of Dams, the State of Missouri, and FEMA have summarized the
status of dams in Missouri by hazard classification. Refer to Figure JF51 (located in the
back of the Technical Appendix) that shows the location of the high hazard dams in
Jefferson County, based on MDNR’s inventory. High hazard is defined as dams that are
more than 30 years old, have a high ratio of maximum storage to dam height and/or high
population density downstream. Table J49 identifies the national and state inventory of
dams. Table J50 lists Jefferson County high hazard dams.
TABLE J49 SUMMARY STATUS OF MISSOURI DAMS BY HAZARD
CLASSIFICATION
NATIONAL INVENTORY STATE REGULATED
Hazard Classification Hazard Classification
Total High Significant Low Total High Significant Low
4095 607 912 2576 630 440 127 63
Source: Missouri Department of Natural Resources