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Town of Lyons Hazard Identification and Risk Assessment August 2017 Town of Lyons Hazard Identification and Risk Assessment August 2017 TABLE OF CONTENTS 1 Background and Purpose ..................................................................... 1 1.1 Overview .......................................................................................................................... 2 2 Hazard Identification .............................................................................. 3 2.1 Planning Area Extent ....................................................................................................... 3 2.2 Hazards Not Included ....................................................................................................... 5 2.3 Declaration History .......................................................................................................... 6 3 Asset Inventory ...................................................................................... 7 3.1 Total Values and Assets at Risk ....................................................................................... 7 4 Hazard Analysis and Risk Assessment.............................................. 16 4.1 Dam Failure .................................................................................................................... 18 4.2 Drought........................................................................................................................... 23 4.3 Earthquakes .................................................................................................................... 34 4.4 Extreme Temperatures ................................................................................................... 44 4.5 Floods ............................................................................................................................. 50 4.6 Hail ................................................................................................................................. 63 4.7 Hazardous Materials Incidents ....................................................................................... 70 4.8 High Winds and Downbursts ......................................................................................... 74 4.9 Landslides, Debris Flows and Rockfalls ........................................................................ 81 4.10 Lightning .................................................................................................................... 87 4.11 Severe Winter Weather ............................................................................................... 93 4.12 Tornadoes ................................................................................................................. 101 4.13 Wildfire ..................................................................................................................... 107 5 Mitigation Action Plan ....................................................................... 122 5.1 Status of Implementation of Mitigation Actions in Related Planning Mechanisms .... 133 5.2 Mitigation Capabilities ................................................................................................. 135 5.3 Implementation............................................................................................................. 137 APPENDIX Appendix A: Public Survey Results Town of Lyons i Hazard Identification and Risk Assessment TOWN OF LYONS HAZARD IDENTIFICATION AND RISK ASSESSMENT 1 BACKGROUND AND PURPOSE The Town of Lyons prepared this Hazard Identification and Risk Assessment (HIRA) to understand areas of vulnerability to hazards and to identify and refine actions which can be taken to reduce the local risk from potential hazards. The HIRA identifies and provides detailed data regarding hazards; inventory assets; analyze risks (potential impacts and estimated losses of each hazard); and assess the Town’s overall vulnerability to hazards. The HIRA is intended to be a resource for planning and resilience capacity building, developed in accordance with the Disaster Mitigation Act of 2000. This document was developed through a planning process between February and July 2017. The development of the HIRA was guided by a HIRA Advisory Committee (Advisory Committee) consisting of staff representing individual Town departments, with assistance and guidance from a consultant, Amec Foster Wheeler. Amec Foster Wheeler was responsible for facilitating the planning process, conducting the general research, developing the risk assessment, and guiding the mitigation strategy to comply with the state and federal mitigation planning regulations and guidance. The Advisory Committee met three times as a group to develop and advise the HIRA. The Advisory Committee included the Town staff from the following departments and interested stakeholders: • Planning • Engineering • Building • Police • Administration • Lyons Prepared • Boulder County Office of Emergency Management • Lyons Fire Protection District • Colorado Department of Local Affairs As part of the HIRA development process a public survey was developed to gather input on hazards and potential mitigation strategies. The results are summarized in Appendix A. Relationship to Other Planning Mechanisms Coordination with other community planning efforts that relates to mitigation of hazards helps build resiliency. The following related statewide, regional, and local planning documents were Town of Lyons 1 Hazard Identification and Risk Assessment August 2017 referenced during the HIRA development including: State of Colorado and Boulder County Hazard Mitigation Plans, Lyons Long-Term Recovery Plan, the St. Vrain Watershed Master Plan, Town of Lyons Recovery Plan and the Town of Lyons Sustainability Action Plan. Other referenced documents include the American Planning Association’s Community Planning Assistance Team final report on ‘Living with the St Vrain,’ developed following the 2013 flood. The HIRA was developed in accordance with FEMA’s 2013 Local Mitigation Planning Handbook as it pertains to conducting a risk assessment and developing a mitigation strategy. 1.1 Overview Risk, as defined by the Federal Emergency Management Agency (FEMA), is a combination of hazard, vulnerability, and exposure. Risk 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 builds upon the methodology described in the 2013 FEMA Local Mitigation Planning Handbook, which recommends a four-step process for conducting a risk assessment: 1) Describe Hazards 2) Identify Community Assets 3) Analyze Risks 4) Summarize Vulnerability Data collected through this process has been incorporated into the following sections of this document: Section 2: Hazard Identification - identifies the natural hazards that threaten the Planning Area and describes why some hazards have been omitted from further consideration. Section 3: Asset Summary - describes the methodology for determining vulnerability of the planning area to the identified hazards. Section 4: Hazard Analysis and Risk Assessment - discusses the threat to the Planning Area and describes previous occurrences of hazard events and the likelihood of future occurrences (2013 FEMA Local Mitigation Planning Handbook Risk Assessment Step 1). It also includes an assessment of the Planning Areas’ exposure to natural hazards; considering assets at risk, critical facilities, and future development trends (2013 FEMA Local Mitigation Planning Handbook Risk Assessment Steps 2, 3 and 4). Town of Lyons 2 Hazard Identification and Risk Assessment Section 5: Mitigation Action Plan – This section discusses a review and update of the mitigation actions specific to the Town, based on the Lyons Annex to the Boulder County Hazard Mitigation Plan. 2 HAZARD IDENTIFICATION Using existing natural hazards data and input gained through planning meetings, the Advisory Committee agreed upon a list of natural and man-made hazards that could affect the Town of Lyons. As a starting point the Advisory Committee reviewed the hazards list from the 2014 Boulder County Hazard Mitigation Plan and the 2013 Colorado Natural Hazards Mitigation Plan. Hazards data from a variety of 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 and 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 hazards worksheet in Table 2.1 was completed by the Advisory Committee to identify, profile, and rate the significance of identified hazards. The hazards of most concern for Lyons includes flood, windstorms and wildfire. Dam failure, drought, hailstorms and winter storms can also have significant impacts. There are also traffic concerns associated
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