Utah Natural Hazards Handbook

1 1 2 Utah Natural Hazards Handbook Coordinated by Utah Division of Homeland Security Author Agencies Utah Geological Survey National Weather Service Salt Lake City Utah Department of Natural Resources Utah Department of Environmental Quality Forest Service Utah Avalanche Center Utah Division of Water Resources Utah Division of Water Rights Utah Division of Forestry, Fire, and State Lands Utah Division of Homeland Security This Handbook was Completed and Distributed October 2008 3 ACKNOWLEDGEMENTS The Utah Natural Hazards Handbook is a summary of various Hazards that exist within Utah. This Handbook was developed with the intention of providing information about specific hazardous events that will assist local emergency managers and local government officials in the identification and understanding of Hazards that threaten their communities.

2 Compilation of this Handbook would not have been possible without the cooperation of numerous state agencies. Special thanks goes out to the authors of each chapter: Susan Elderedge, Gary C. Christenson, Kimm M. Harty, Richard E. Giraud, and William E. Mulvey (Utah Geological Survey); David Neville and John Hultquist (Utah Department of Environmental Quality); Kevin Barjenbruch and Brian McInerney (National Weather Service, Salt Lake City); Matthew Lindon (Utah Division of Water Rights); Bruce Tremper, Evelyn Lees, and Liam Fitzgerald (Utah Avalanche Center); Brian King (Utah Division of Water Resources); and Tracy Dunford and Tyre Holfeltz (Division of Forestry, Fire, and State Lands). Special thanks also goes out to Brad Bartholomew, Nancy Barr, Judy Watanabe, Bob Carey, John Crofts, Amisha Lester, Sean McMillian, Laura Siebeneck (Utah Division of Homeland Security), and Laura Ault (Forestry, Fire and State Lands) for their assistance in compiling the chapters and editing.

3 In addition, we want to extend our thanks to the members of the State Hazard Mitigation Team for their helpful input and feedback. This version of the Utah Natural Hazards Handbook is an updated version of the Handbook created in July 1991 for use at the Utah Natural Hazards Training Workshop. 4 TABLE OF CONTENTS Introduction .. Laura Siebeneck, Utah Division of Homeland Security 1 Earthquakes .. Sandra N. Eldredge, Utah Geological Survey Gary C. Christenson, Utah Geological Survey 3 Landslides .. Sandra N. Eldredge, Utah Geological Survey Kimm M. Harty, Utah Geological Survey Richard E. Giraud, Utah Geological Survey 16 Problem Soils and Rock .. Sandra N. Eldredge, Utah Geological Survey William E. Mulvey, Utah Geological Survey Gary C. Christenson, Utah Geological Survey 26 Radon Gas.

4 David Neville, Utah Department of Environmental Quality John Hultquist, Utah Department of Environmental Quality 36 Weather Hazards : Lightning, Severe Thunderstorms, and Winter Storms Kevin Barjenbruch, National Weather Service Salt Lake City Brian McInerney, National Weather Service Salt Lake City 45 Kevin Barjenbruch, National Weather Service Salt Lake City Brian McInerney, National Weather Services Salt Lake City Judy Watanabe, Utah Division of Homeland Security Laura Siebeneck, Utah Division of Homeland Security 58 Dam Safety and Risk .. Matthew Lindon, Utah Division of Water Rights 68 Snow Avalanche .. Bruce Tremper, Utah Avalanche Center Evelyn Lees, Utah Avalanche Center Liam Fitzgerald, Utah Avalanche Center 88 Drought.

5 Brian King, Utah Division of Water Resources. 95 Wildfire .. Tracy Dunford, Division of Forestry, Fire, and State Lands Tyre Holfeltz, Division of Forestry, Fire, and State Lands 109 Appendices Glossary .. Selected List of Agencies .. 119 130 1A home destroyed by flooding of the Santa Clara River in the Green Valley area of St. George, Utah, Jan. 12, 2005. (AP Photo/Joe Cavaretta) What is a Natural Hazard? Traditionally, a Natural hazard is defined as an event that causes harm to people and the things they value. It is an environmental phenomenon that can be induced by atmospheric, hydrologic, geologic, and wildfire-related occurrences. The level of risk associated with these Hazards varies by location, season, and probability of a particular hazard occurring. The State of Utah experiences a variety of Natural hazard events that differ in magnitude, duration, and geographic location.

6 Some of these events can be forecasted while others occur with little or no warning. Depending on their location, citizens of Utah are at risk to a wide array of Natural hazard events including weather-related events, floods, dam failures, snow avalanches, earthquakes, slope failures, landslides, wildfires, radon gas exposure, and drought. Utah s Natural Hazards Throughout the last decade, Utah has experienced numerous hazard events. The events described below are disasters in which a Presidential disaster Declaration was issued. - On August 11, 1999, an F-2 tornado struck downtown Salt Lake City. The tornado developed on the western side of downtown and moved northeast before expiring near Memory Grove Park. This event resulted in one death and 80 injuries. In addition, 300 buildings or houses were damaged, 34 of the homes were rendered uninhabitable, and 500 trees were destroyed.

7 Total damage estimates for this storm were $170 million and federal assistance was provided. - On the dates of January 8-12, 2005, a stalled storm-system containing abundant moisture caused significant flooding in Washington and Kane counties in Southern Utah. This event caused an estimated $300 million dollars in damage along the Santa Clara and Virgin Rivers in Washington County, including the Green Valley area of St. George as well as homes in the town of Santa Clara, Utah. Thirty homes were destroyed in the flood and another 20 homes were significantly damaged (NCDC, 2005). One fatality was associated with this event and six other injuries were reported. In addition, avalanches due to a considerable amount of wet, heavy snow that fell in the Salt Lake City Tornado, August 11, 1999. (Photo courtesy of KTVX News 4 Utah) 2higher mountain elevations during these storms also resulted in two fatalities.

8 A Presidential disaster Declaration was declared February 1, 2005. - Between April 28, 2005 until June 29, 2005, frequent rainfall events, warm spring temperatures, and abundant snowpack melting at accelerated rates resulted in significant flooding and landslide events in nine Utah counties and two Indian Reservations. Peak discharge in the Little Bear River exceeded the 100-year recurrence interval. Large peak discharges in spring of 2005 in the Duchesne and Sevier River basins were the result of near record snowpacks (USGS, 2005). Total damage resulting from the flooding and landslide incidents are estimated to be over million dollars. No deaths have been attributed to the flooding and landslide events, though there was substantial damage to public and private property, roads, and bridges. In addtion, concerns of health risks such a vector born diseases transmitted by mosquitoes arose.

9 A Presidential disaster Declaration was declared on August 1, 2005 and included Beaver, Box Elder, Iron, Kane, Sevier, Tooele, Uintah, and Wasatch counties and the Uintah and Ouray Indian Reservations. How to Reduce Risks As demonstrated above, losses associated with Natural Hazards can be costly. Efforts can be made to reduce the amount of losses sustained to a community prior to the onset of the disaster . While many Natural Hazards cannot be avoided, damage to property, infrastructure, and loss of life can be reduced through effective implementation of mitigation strategies. The Division of Emergency Services and Homeland Security Hazard Mitigation Section is working with local communities, governments, and businesses to develop and promote hazard mitigation activities in the state. Efforts include active participation and support of the Utah Earthquake Preparedness Information Center (EPIC enter) which promotes seismic safety statewide through community outreach programs, Utah Seismic Safety Commission, National Flood Insurance Program, Hazard Mitigation Grant Program and the Pre- disaster Mitigation Program.

10 The Homeland Security website includes information about specific hazard mitigation programs, Hazards specific to Utah, mitigation publications, The State hazard mitigation Plan, and links to other hazard mitigation-related web sites. This site can be found at the following address: Purpose and Use of the Handbook This Handbook is comprised of nine chapters, each related to a specific Natural hazard and one technological hazard (dam failure). The chapters were written by experts from various Utah agencies and compiled by the Utah Division of Homeland Security. The goal of this Handbook is to provide a useful synthesis of Natural Hazards in Utah that can be used by local government officials (elected officials, public works personnel, land-use planners, etc.) as well as local emergency managers to better understand and identify what Natural Hazards pose greatest risk to their communities.