Jefferson County - East-West Gateway Coordinating Council

A Regional Overview All-Hazard Mitigation Plan 131
HAZARD ANALYSIS NARRATIVE
Hazard: Flood
Description of Hazard (Type of hazard, pathways/areas likely affected, type of damage,
etc.) A flood is defined as an overflow or inundation that comes from a river or other
body of water or causes or threatens damage, or any relatively high streamflow that
overtops the natural or artificial banks in any reach of stream. The National Flood Insurance
Program defines a flood as a general and temporary condition of partial or complete
inundation of two or more acres of normally dry land or of two or more properties from
inland waters, unusual and rapid accumulation or runoff of waters from any source or a
mudflow. Floods are most likely to occur in the spring, but can occur in any time of the
year. Any person or structure that is present in the path of floodwaters as described above
could be damaged. Damage is most likely to occur within the flood insurance rate map
designated 100 and 500-year areas. The amount of damage depends on 1). The
intensity/strength of the flood, 2). The proximity of the flood to the person/structure.
Damage can range from very slight to total. Hazards range from death to total property
damage from floodwaters.
Historical Statistics (Frequency, strength, # of lives lost, # of injuries, economic losses,
etc.) The East-West Gateway Coordinating Council planning region has many river and
small tributaries in both the unincorporated and incorporated areas that are susceptible to
flooding. Catastrophic floods have occurred in the EWGCC region in 1927, 1951, 1973,
1979, 1982, 1984, 1986, 1993, 1994, 1994, 1995, 1998, 1999 and 2000. In the
Chesterfield Valley of St. Louis County alone, damage from the 1993 flood totaled $200
million. (In the 1993 flood approximately $21 billion dollars in damage and costs and 48
deaths resulted (NOAA.) Multiple lives have been lost from flooding; 49 deaths were
recorded from the 1993 Flood.
Statement of Future Probable Severity (Catastrophic/Critical/Limited/Negligible) Critical
Statement of Probable Risk (Likeliness of future occurrence- (Highly
Likely/Likely/Possible/Unlikely)-Highly Likely to occur in future
Statement of Next Disaster’s Likely Adverse Impact on the Community
(Catastrophic/Critical/Limited/Negligible)
Without mitigation measures: Life Property Emotional Financial
Comments:
Catastrophic Catastrophic Catastrophic Catastrophic
With mitigation measures: Life Property Emotional Financial