All Hazard Mitigation Plan Twin Falls County, Idaho
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2008 TWIN FALLS COUNTY ALL HAZARD MITIGATION PLAN OCTOBER 15, 2008 Preface The Twin Falls County All Hazard Mitigation Plan was developed in late fall of 2006 through the spring of 2008. It contains information pertaining to the hazards and hazard vulnerabilities faced by Twin Falls County. This Plan is designed to interface with the State of Idaho Multi-Hazard Mitigation Plan published in November 2004 and updated in November 2007. This Plan has been developed as the Twin Falls County All Hazards Mitigation Plan (AHMP) however; the Plan was developed by an integrated effort from representatives from many of the jurisdictions in Twin Falls County. Each City will therefore be asked to endorse the AHMP and in turn participate in implementation of the Plan as it applies to the hazards in their respective jurisdictions. Further updates of this Plan will seek to increase multi-jurisdiction involvement. Twin Falls 1 All Hazard Mitigation Plan October 15, 2008 This Page Intentionally Blank Twin Falls 2 All Hazard Mitigation Plan October 15, 2008 Twin Falls 3 All Hazard Mitigation Plan October 15, 2008 This Page Intentionally Blank Twin Falls 4 All Hazard Mitigation Plan October 15, 2008 Twin Falls 5 All Hazard Mitigation Plan October 15, 2008 This Page Intentionally Blank Twin Falls 6 All Hazard Mitigation Plan October 15, 2008 This Page Intentionally Blank Twin Falls 7 All Hazard Mitigation Plan October 15, 2008 This Page Intentionally Blank Twin Falls 8 All Hazard Mitigation Plan October 15, 2008 Twin Falls 9 All Hazard Mitigation Plan October 15, 2008 This Page Intentionally Blank Twin Falls 10 All Hazard Mitigation Plan October 15, 2008 Twin Falls 11 All Hazard Mitigation Plan October 15, 2008 This Page Intentionally Blank Twin Falls 12 All Hazard Mitigation Plan October 15, 2008 Twin Falls 13 All Hazard Mitigation Plan October 15, 2008 This Page Intentionally Blank Twin Falls 14 All Hazard Mitigation Plan October 15, 2008 Twin Falls 15 All Hazard Mitigation Plan October 15, 2008 This Page Intentionally Blank Twin Falls 16 All Hazard Mitigation Plan October 15, 2008 Twin Falls 17 All Hazard Mitigation Plan October 15, 2008 This Page Intentionally Blank Twin Falls 18 All Hazard Mitigation Plan October 15, 2008 Twin Falls 19 All Hazard Mitigation Plan October 15, 2008 This Page Intentionally Blank Twin Falls 20 All Hazard Mitigation Plan October 15, 2008 Twin Falls 21 All Hazard Mitigation Plan October 15, 2008 This Page Intentionally Blank Twin Falls 22 All Hazard Mitigation Plan October 15, 2008 Table of Contents Preface ……………………………………………………………. 1 Promulgation of Adoption ……………………………………….. 3 FEMA Final Approval ……………………………………………. 5 Letters of Endorsement ……………………………………………. 7 Section 1 Planning Process ………………………………………. 25 Section 2 Community Description………………………………... 39 Section 3 Public Involvement …………………………………….. 53 Section 4 Risk Assessment ……………………………………….. 65 Section 4.1Weather Hazards ……………………………… 66 Section 4.2 Flooding ……………………………………… 101 Section 4.3 Geological Hazards …………………………... 116 Section 4.4 Other Natural Hazards ……………………….. 130 Section 4.5 Technological (Manmade) Hazards ………… 144 Section 4.6 Vulnerabilities ……………………………….. 161 Section 4.7 Risk Summary ……………………………….. 183 Section 5 Land Use Planning and Hazard Mitigation Integration... 191 Section 6 Mitigation Projects and Implementation Roadmap ……. 193 Attachments ……………………………………………………….. 219 Twin Falls 23 All Hazard Mitigation Plan October 15, 2008 This Page Intentionally Blank Twin Falls 24 All Hazard Mitigation Plan October 15, 2008 Section 1 Planning Process Introduction Twin Falls County, Idaho and the incorporated cities that lie within the County boundaries are vulnerable to natural, technological, and man-made hazards that have the potential to cause serious harm to the health, welfare, and security of its residents. The cost of response to and recovery from disaster events can be lessened when attention is turned to mitigating their impacts and effects before they occur or re-occur. This Plan seeks to identify the County‘s hazards, understand the vulnerabilities to those hazards, and craft solutions that, if implemented, will significantly reduce threats to life and property. The Plan is based on the premise that hazard mitigation works! With increased attention to managing natural hazards, communities can reduce the threats to citizens and, through proper land use and emergency planning, avoid creating new problems in the future. Many solutions can be implemented at minimal cost and social impact. This is not an emergency response or management plan. The Plan can certainly be used to identify weaknesses and refocus emergency response planning. Enhanced emergency response planning is an important mitigation strategy. The focus of this Plan, however, is to support better decision making directed toward avoidance of future risk and to implement activities or projects that will eliminate or reduce current risks. Plan Organization Section 1 of the Plan provides a general overview of the process, the scope, purpose, and overall goals of the plan. Section 2 of the Plan gives a general background or description of the County‘s demographic, economic, cultural, and physiographic characteristics. Section 3 documents the public involvement component of the Plan. Section 4, the Risk Assessment section, provides a brief definition for each natural hazard. All hazards identified as affecting the County are analyzed at the County and incorporated City level and then summarized. For expanded definitions of the analyzed hazards refer to the State of Idaho Hazard Mitigation Plan as adopted in November 2007. Section 5 provides a review of the County Land Use Ordinances and Comprehensive Plan and provides suggestions for integration between this All Hazard Mitigation Plan (AHMP) and the Land Use Planning efforts in the County. Section 6 presents selected Mitigation Alternatives with supporting project descriptions and a ―roadmap‖ to implementation. Twin Falls 25 All Hazard Mitigation Plan October 15, 2008 Plan Use The Plan should be used to help County and City officials plan, design, and implement programs and projects that will help reduce the jurisdiction‘s vulnerability to natural and technological (manmade) hazards. The Plan should also be used to facilitate inter- jurisdictional coordination and collaboration related to all hazard mitigation planning and implementation within the County and at the Regional level. Lastly, the Plan should be used to develop or provide guidance for local emergency response planning. If adopted, this Plan will achieve compliance with the Disaster Mitigation Act of 2000. Hazard Mitigation Hazard mitigation is defined as cost-effective actions that have the effect of reducing, limiting, or preventing the vulnerability of people, culture, property, and the environment to potentially damaging, harmful, or costly hazards. Hazard mitigation measures which can be used to eliminate or minimize the risk to life, culture and property, fall into three categories: 1) Those that keep the hazard away from people, property, and structures, 2) Those that keep people, property, or structures away from the hazard, and 3) Those that reduce the impact of the hazard on victims, i.e., insurance. Hazard mitigation measures must be practical, cost effective, and culturally, environmentally, and politically acceptable. Actions taken to limit the vulnerability of society to hazards must not, in themselves, be more costly than the anticipated damages. Hazard mitigation planning must be based on vulnerabilities and its primary focus must be on the point where capital investment and land use decisions are made. The placement of capital investments, whether for homes, roads, public utilities, pipelines, power plants, or public works, determine to a large extent the nature and degree of a community‘s hazard vulnerability. Once a capital facility is in place, there is little opportunity to reduce hazard vulnerability through correction of errors in location or construction. It is for this reason that often the most effective mitigation tools are zoning and other ordinances that manage development in high vulnerability areas, and building codes that ensure that new buildings are constructed to withstanding the damaging forces of anticipated hazards. Because disaster events are generally infrequent, the nature and magnitude of the threat is often ignored or poorly understood. Thus, the priority to implement mitigation measures is low and implementation is slowed. Mitigation success can be achieved, however, if accurate information is portrayed through complete hazard identification and impact studies, followed by effective mitigation management. The Federal Emergency Management Agency has identified hazards to be analyzed by each jurisdiction, completing an All Hazard Mitigation Plan. The hazards analyzed in this Plan include the following: Twin Falls 26 All Hazard Mitigation Plan October 15, 2008 Natural Hazards Weather: Drought Extreme Heat Extreme Cold Severe Winter Storm Lightning Hail Tornado Straight Line Wind Flooding: Flash Flood River Flooding Dam Failure Geologic: Earthquake Landslide/Mudslide Other: Wildfire Biological Pandemic/Epidemic Bird Flu SARs West Nile Technological (Manmade) Hazards Structural Fire Nuclear Event Hazardous Material Event Riot/Demonstration/Civil Disorder Terrorism Purpose The purposes of this Plan are to: Fulfill Federal and local mitigation planning responsibilities; Promote pre- and post-disaster mitigation measures with short/long