Chapter 4 Risk Assessment
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Chapter 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 community’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 identifies the 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 and impacts 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, future development trends, and, where possible, estimates potential hazard losses. ➢ Section 4.4: Capability Assessment inventories existing mitigation activities and policies, regulations, plans, and projects that pertain to mitigation and can affect net vulnerability. This risk assessment covers the entire geographical extent of unincorporated Lake County (i.e., the Lake County Planning Area). And as required by FEMA, this risk assessment for the Lake County Planning Area also includes an evaluation of how the hazards and risks vary across the Planning Area. Lake County Public Review Draft 4-1 Local Hazard Mitigation Plan Update January 2018 This LHMP Update involved a comprehensive review and update of each section of the 2012 risk assessment. As part of the risk assessment update, new data was used, where available, and new analyses were conducted. Where data from existing studies and reports was used, the source is referenced throughout this risk assessment. Refinements, changes, and new methodologies used in the development of this risk assessment update are summarized in Chapter 2 What’s New and also detailed in this risk assessment portion of the plan. 4.1 Hazard Identification 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 Lake County Hazard Mitigation Planning Committee (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. Data Sources The following data sources were used for this Hazard Identification portion of the plan: ➢ HMPC input ➢ National Climatic Data Center Storm Events Database ➢ 2012 Lake County Hazard Mitigation Plan ➢ 2013 State of California Hazard Mitigation Plan ➢ 2017 Draft Lake County Emergency Operations Plan ➢ FEMA Disaster Declaration Database 4.1.1. Results and Methodology Using existing hazards data and input gained through planning meetings, the HMPC agreed upon a list of hazards that could affect Lake County. Hazards data from the California Office of Emergency Services (Cal OES), FEMA, California Department of Water Resources, 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 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. Only the more significant (or priority) hazards have a more detailed hazard profile and are analyzed further in Section 4.3 Vulnerability Assessment. The following hazards in Table 4-1, listed alphabetically, were identified and investigated for this LHMP Update. As a starting point, the 2013 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 2012 plan were profiled in this Plan Update. Some hazards were Lake County Public Review Draft 4-2 Local Hazard Mitigation Plan Update January 2018 reclassified and added to: water shortage was added to the drought hazard, quagga mussels were added with cyanobacterial bloom in as aquatic biological hazard, and geothermal gas release was expanded in the volcano hazard. New hazards include agricultural hazards, climate change, hazardous materials transportation, and subsidence. Table 4-1 Lake County Hazard Identification and Comparison 2017 Hazards 2012 Hazards Comment Agricultural Hazards – New hazard. Aquatic Biologic Hazards: Cyanobacterial Greater analysis was performed based on monitoring cyanobacterial bloom bloom data from the County. Aquatic Biologic Hazards: quagga – New hazard mussel Climate Change – New hazard. Dam Failure Dam Failures Dam inundation analysis was performed. Drought and Water Shortage Drought The water shortage discussion was added. Additional vulnerability discussion was added. Earthquake Earthquake A Hazus analysis was performed to add to the vulnerability discussion. Flood: 1%/0.2% Annual Chance Floods DFIRM flood analysis was performed. Assets at risk, populations at risk, and critical facilities at risk to flooding were analyzed. Flood: Localized/Stormwater Localized Flooding Additional discussions of specific areas of localized flooding were discussed. Hazardous Materials Transportation – New hazard. Landslide and Debris Flows Landslides A greater analysis was performed using GIS. Values at risk, populations at risk, and critical facilities were analyzed. Levee Failure Levee Failure (as The hazard was broken out from the flood hazard and part of flood) a larger discussion of levee failure in the County was added. Severe Extreme Heat – New hazard. Severe Weather: Heavy Rains, Snow, Severe Storms Similar analysis was performed. and Storms (winds, hail, lightning) Subsidence – New hazard. Volcano Volcano Eruption/ Additional discussions regarding vulnerability were Geothermal Gas added. Included additional information on the Release Geothermal Gas hazard. Wildfire Fire Additional analysis was performed on the fire hazard severity zone layer. Assets at risk, populations at risk, and critical facilities at risk to wildfire were analyzed. Lake County Public Review Draft 4-3 Local Hazard Mitigation Plan Update January 2018 Table 4-2 was completed by the County and 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 4-35 in Section 4.2.20 Natural Hazards Summary provides an overview of these significant hazards. Lake County Public Review Draft 4-4 Local Hazard Mitigation Plan Update January 2018 Table 4-2 Lake County Hazard Identification Probability of Climate Geographic Future Magnitude/ Change Hazard Extent Occurrences Severity Significance Influence Agricultural Hazards Significant Highly Likely Limited High Medium Aquatic Biological Hazards: Significant Highly Likely Limited High High cyanobacterial bloom Aquatic Biological Hazards: quagga Significant Likely Critical High High mussel Climate Change Extensive Likely Limited High – Dam Failure Limited Occasional Limited High Low Drought and Water Shortage Extensive Likely Critical High Medium Earthquake Extensive Likely Critical High Low Flood: 1%/0.2% Annual Chance Limited Occasional/Unlikely Limited High Medium Flood: Localized/Stormwater Limited Likely Limited Medium Medium Hazardous Materials Transport Limited Likely Limited Medium Low Landslide and Debris Flows Significant Likely Limited Medium Medium Levee Failure Significant Likely Limited Medium Medium Severe Weather: Extreme Heat Significant Likely Critical Medium Medium Severe Weather: Heavy Rains, Snow, Significant Highly Likely Critical High High and Storms Severe Weather: High Winds Significant Likely Critical High Low Subsidence Limited Occasional Limited Low Low Volcano Significant Unlikely Critical High Low Wildfire Significant Highly Likely Critical High High Geographic Extent Magnitude/Severity Limited: Less than 10% of planning