4 RISK ASSESSMENT Requirement §201.6(c)(2): [The plan shall include] A risk assessment that provides the factual basis for activities proposed in the strategy to reduce losses from identified hazards. Local risk assessments must provide sufficient information to enable the jurisdiction to identify and prioritize appropriate mitigation actions to reduce losses from identified hazards. As defined by the Federal Emergency Management Agency (FEMA), risk is a combination of hazard, vulnerability, and exposure. It is the impact that a hazard would have on people, services, facilities, and structures in a community and refers to the likelihood of a hazard event resulting in an adverse condition that causes injury or damage. The risk assessment process identifies and profiles relevant hazards and assesses the exposure of lives, property, and infrastructure to these hazards. The process allows for a better understanding of a jurisdiction‘s potential risk to natural hazards and provides a framework for developing and prioritizing mitigation actions to reduce risk from future hazard events. This risk assessment followed the methodology described in the FEMA publication Understanding Your Risks—Identifying Hazards and Estimating Losses (FEMA 386-2, 2002), which breaks the assessment down to a four-step process: 1) Identify Hazards; 2) Profile Hazard Events; 3) Inventory Assets; and 4) Estimate Losses. Data collected through this process has been incorporated into the following sections of this chapter: Section 4.1: Hazard Identification: Natural Hazards identifies the natural hazards that threaten the planning area and describes why some hazards have been omitted from further consideration. Section 4.2: Hazard Profiles discusses the threat to the planning area and describes previous occurrences of hazard events and the likelihood of future occurrences. Section 4.3: Vulnerability Assessment assesses the planning areas‘ exposure to natural hazards; considering assets at risk, critical facilities, and future development trends. Section 4.4: Capability Assessment inventories existing mitigation activities and policies, regulations, and plans that pertain to mitigation and can affect net vulnerability. This risk assessment covers the entire geographical extent of the Butte County Planning Area (planning area), including the incorporated communities and other participating jurisdictions. Since this plan is a multi-jurisdictional plan, the Hazard Mitigation Planning Committee (HMPC) is required to evaluate how the hazards and risks vary from jurisdiction to jurisdiction. While these differences are noted in this chapter, they are expanded upon in the annexes of the participating jurisdictions. If no additional data is provided in an annex, it should be assumed Butte County 4.1 Local Hazard Mitigation Plan Update May 2013 that the risk and potential impacts to the affected jurisdiction are similar to those described here for the entire Butte County Planning Area. This Local Hazard Mitigation Plan (LHMP) update involved a comprehensive review and update of each section of the 2007 risk assessment. As part of the risk assessment update, new data was used, where available, and new analyses were conducted. Refinements, changes, and new methodologies used in the development of this risk assessment update are summarized in Chapter 2 What‘s New and detailed in this Risk Assessment portion of the plan. 4.1 Hazard Identification: Natural Hazards Requirement §201.6(c)(2)(i): [The risk assessment shall include a] description of the type…of all natural hazards that can affect the jurisdiction. The Butte County HMPC conducted a hazard identification study to determine the hazards that threaten the planning area. This section details the methodology and results of this effort. 4.1.1 Methodology and Results Using existing natural hazards data and input gained through planning meetings, the HMPC agreed upon a list of natural hazards that could affect Butte County. Hazards data from the California Emergency Management Agency (CAL EMA), FEMA, the National Oceanic and Atmospheric Administration (NOAA), and many other sources were examined to assess the significance of these hazards to the planning area. Significance of each identified hazard was measured in general terms and focused on key criteria such as frequency and resulting damage, which includes deaths and injuries, as well as property and economic damage. The natural hazards evaluated as part of this plan include those that have occurred historically or have the potential to cause significant human and/or monetary losses in the future. The following hazards in Table 4.1, listed alphabetically were identified and investigated for this plan update. As a starting point, the updated California State Hazard Mitigation Plan was consulted to evaluate the applicability of new hazards of concern to the State to the planning area. Building upon this effort, hazards from the past plan were also identified, and comments explain how hazards were updated from the previous plan. Most hazards from the 2007 plan were profiled in this plan, with the exception of the naturally occurring biological threats and the domestic security threat of terrorism, which has been eliminated from further consideration in this natural hazards plan, as they have been addressed in other state, regional, and County planning mechanisms. Butte County 4.2 Local Hazard Mitigation Plan Update May 2013 Table 4.1. Hazard Identification and Comparison 2013 Hazards 2007 Hazards Comment Dam Failure Dam Failure Performed dam inundation analysis in both map and tabular form. Drought & Water Shortage Extreme Weather (drought/heavy Added water shortage discussion rain/hailstorm/windstorm/tornado Earthquakes Earthquake Added liquefaction analysis and discussion. Earth Movements: Landslide Landslide Similar analysis was performed Earth Movements: Erosion – New hazard Floods: 100/500 year Floods* Performed greater analysis on 100 year flood. Added analysis on 500 year flood. Floods: Localized Stormwater – New hazard Hazardous Materials Incidents: Hazardous Materials Incidents A greater focus on transportation routes Transportation was given. Analysis was performed on populations in the hazardous materials routes in the County. Invasive Species: Pests/Plants Insect Infestation Added invasive plant species discussion Levee Failure – New hazard Marine Invasive Species – New hazard Severe Weather: Extreme Heat – New hazard (though mentioned in the 2007 plan drought profile) Severe Weather & Storms: Extreme Weather (drought/heavy Similar analysis was performed. Heavy rain, hailstorm, lightning rain/hailstorm/windstorm/tornado) Severe Weather: Tornado Extreme Weather (drought/heavy Similar analysis was performed. rain/hailstorm/windstorm/tornado) Severe Weather: Windstorms Extreme Weather (drought/heavy Similar analysis was performed. rain/hailstorm/windstorm/tornado Severe Weather: Winter Storm/ – New hazard Freeze Volcanoes – New hazard Wildfires Wildfires Greater analysis was performed. – Naturally Occurring Biological This has been eliminated from this plan. Threats They have been kept for reference purposes in Appendix H. – Terrorism (CBRNE), Chemical, These have been eliminated from this plan, Biological, Radiological, Nuclear, and will be included in County Response Explosive Planning. They have been kept for reference purposes in Appendix H. The worksheet below was completed by the HMPC to identify, profile, and rate the significance of identified hazards. Only the more significant (or priority) hazards have a more detailed hazard profile and are analyzed further in Section 4.3 Vulnerability Assessment. Table 4.29 in Section 4.2.19 Natural Hazards Summary provides an overview of these significant hazards. Butte County 4.3 Local Hazard Mitigation Plan Update May 2013 Table 4.2. Butte County Hazard Identification Worksheet Probability of Geographic Hazard Future Magnitude/Severity Significance Extent Occurrences Dam Failure Significant Unlikely Critical Medium Drought & Water shortage Extensive Occasional Critical Medium Earthquakes Extensive Occasional Critical Medium Earth Movements: Landslide Limited Likely Negligible Low Earth Movements: Erosion Limited Highly Likely Significant Medium Floods: 100/200/500 year Significant Occasional Critical High Floods: Localized Stormwater Extensive Highly Likely Critical Medium Hazardous Materials Significant Likely Critical Medium Incidents: Transportation Invasive Species: Pests/Plants Significant Highly Likely Limited Low Levee Failure Significant Occasional Limited High Marine Invasive Species Limited Occasional Limited Low Severe Weather: Extreme Significant Highly Likely Critical Low Heat Severe Weather: Freeze and Significant Highly Likely Critical Medium Winter Storm Severe Weather: Heavy rain, Significant Highly Likely Critical Medium hailstorm, lightning Severe Weather: Tornado Limited Likely Limited Low Severe Weather: Windstorms Extensive Highly Likely Critical Medium Volcanoes Significant Unlikely Critical Low Wildfires Significant Highly Likely Critical High Geographic Extent Magnitude/Severity Limited: Less than 10% of planning area Catastrophic—More than 50 percent of property severely Significant: 10-50% of planning area damaged; shutdown of facilities for more than 30 days; and/or Extensive: 50-100% of planning area multiple deaths Critical—25-50 percent of property severely damaged; Probability of Future Occurrences shutdown of facilities for at least two weeks; and/or injuries Highly Likely: