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30 homes lost, lessons learned from the 2005 Santa Clara Utah river flood

Kelly Bringhurst, Physical Sciences, Dixie State University

Summary

Water availability in the desert southwest is sporadic, alternating between years of drought and occasional heavy periods of precipitation. Stream channels in these areas have developed broad floodplains and alluvial deposits that are occasionally reworked. Analyzing risk along streams requires knowledge both of flood and stream bank erosion hazards.

A southerly Pacific storm track attributed to a weak El Niño event predominated the weather pattern in January of 2005 in southwestern Utah. Heavy rains fall on snowpack laid down the previous week, resulting in rapidly rising stream discharge. The Santa Clara river, normally a small stream easily jumped became a torrent a hundred yards wide in places. While the discharge was less than expected for the 100-year flood, erosion due to changes in meanders cut into neighborhoods adjacent to the river. Approximately 20 homes were washed away and another 10 were damaged beyond repair. Since most homes were above the 100-year floodplain, most home owners neglected to purchase flood insurance.

The community came together to help those impacted by this disaster. Fund raising over the next year helped compensate those who lost homes. A Master Plan for reconstruction, management, and long-term maintenance of the Santa Clara river channel was developed. Publications detailing the hazard of stream bank erosion along with flooding have been produced. Informational materials produced as a result of this disaster provide critical information for those who seek it. Unfortunately, as with most natural disasters, the public has a short term memory. People again are interested in building near what appears to be a serene, small stream.

Individuals with expertise/responsibilities in the following areas have helped create the case study:

Key teaching points:
  • Floodplain characteristics and understanding FEMA flood hazard maps.
  • Changes to meander patterns of streams, stream erosion and deposition.
  • Variability in precipitation patterns in arid regions.
  • Importance of evaluating risk prior to purchase of property.

How this example is used in the classroom:
Worldwide, average annual death tolls and property damage is highest in flood events when compared to other natural disasters. The local example of flooding in southwestern Utah during January of 2005 led to one death and damage of approximately $200 million dollars. This flood event is then compared to larger floods and the toll it takes on people worldwide.

References

Photos and charitable donations:
http://www.utahfloodrelief.com/need.html

Flood hazard maps:
http://geology.utah.gov/maps/geohazmap/washington.htm

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