# Chehalis Reservation > Briefs, arguments, decisions, and more. URL: https://www.frixlaw.com/law-library/documents/tribal%3Aconfederated_chehalis%3Aadf9872bdd7a0975 ## Record - **Collection:** Tribal code - **Document type:** Tribal code ## Text Chehalis Reservation Natural Hazards Mitigation Plan 2009 Table of Contents/Introduction Page 1 Table of Contents/Introduction Page 2 This page intentionally left blank Table of Contents/Introduction Page 3 TABLE OF CONTENTS Authorizing Resolution/Table of Contents Authorizing Resolution ............................................................................ 2 Table of Contents ................................................................................... 4 Chapter 1: Introduction Introduction .......................................................................................... 8 Chapter 2: Planning Process Planning Process .................................................................................... 10 Table 1.1 Jurisdiction Adoption and Approval Dates of the 20032008 Hazard Mitigation Plan for the Thurston Region .......... 10 Table 1.2 2008-2009 Hazard Mitigation Planning Workgroup for the Confederated Tribes of the Chehalis Reservation .......... 11 Plan Update 2008-2009 .......................................................................... 12 Chehalis Reservation Community Process .................................................. 13 Natural Hazards Preparedness Questionnaire ............................................. 16 Chapter 3: Chehalis Reservation Profile Tribal Government ................................................................................. 21 Table 2 Chehalis Tribe Employees ......................................... 22 Statistical Profile .................................................................................... 23 Socio –Economic .................................................................................... 23 Tribal Lands .......................................................................................... 24 Historic/Traditions/Culture ...................................................................... 25 Chapter 4: Risk Assessment Risk Assessment Introduction .................................................................. 27 Table 3.1 Hazard/Risk Rating ............................................... 27 P’ucú/Flood – Identification & Profile ......................................................... 30 Table 3.2 Historical Flood Events Table .................................. 32 Identification and Profile ............................................................... 34 Characteristics of Flooding ............................................................. 34 Flood – Historic Profile .................................................................. 36 Table 3.3 USGS Advanced Hydrologic Prediction Service: Seattle, Chehalis River near Grand Mound, Flood Categories 37 Table 3.4 USGS Advanced Hydrologic Prediction Service: Seattle, Chehalis River at Centralia Flood Categories .......... 38 Topography ................................................................................. 40 Soil Types on the Chehalis Reservation............................................ 41 Impacts ...................................................................................... 42 Data/Chehalis Community Awareness ............................................. 44 Yakwa†t&mx/Earthquake - Identification and Profile ................................... 45 Geology ...................................................................................... 47 Earthquake – Historic Profile .......................................................... 49 Table 3.5 FEMA Disaster Assistance Totals July 31, 2001.......... 51 Table of Contents/Introduction Page 4 Future Earthquake Potential........................................................... 52 Impacts ...................................................................................... 52 Chehalis Community Awareness ..................................................... 54 Severe Winter Storm – Identification & Profile ............................................ 55 Severe Storm – Historic Profile....................................................... 57 Future Severe Storm Potential ....................................................... 58 Impacts ...................................................................................... 58 Data/Chehalis Community Awareness ............................................. 59 Volcano – Identification & Profile .............................................................. 60 Volcano – Historic Profile ............................................................... 60 Impacts ...................................................................................... 63 Data/Chehalis Community Awareness ............................................. 63 Wildfire – Identification & Profile .............................................................. 65 Wildfire – Historic Profile ............................................................... 65 Impacts ...................................................................................... 66 Data/Chehalis Community Awareness ............................................. 66 Climate Change ..................................................................................... 67 Assessing Vulnerabilities - Identifying Structures ........................................ 69 Transportation Facilities ................................................................ 70 Table 3.6 Chehalis Reservation IRR Inventory ........................ 73 Table 3.7 Chehalis Reservation Bridge Inventory..................... 84 Estimating Potential Losses............................................................ 90 Table 3.8 Chehalis Tribe 2007-2008 COPE Table ..................... 91 Analyzing Development Trends ...................................................... 101 Land Use Criteria................................................................ 102 Primary Land Use Designations ............................................ 102 Summary of Proposed Development Zones ............................ 104 Summary of Tribal Land Use Goals and Objectives ............................ 106 Assessing Vulnerabilities - Assessing Cultural and Sacred Sites ..................... 107 Plan Incorporation and Coordination ......................................................... 107 Chapter 5: Mitigation Strategy Identification & Analysis of Tribal Mitigation Actions .................................... 108 Mitigation Plan goals............................................................................... 109 Identification and Prioritization of Mitigation Initiatives ................................ 110 Implementation of 2004 Plan Tribal Mitigation Actions ................................. 111 Tribal Capacity Assessment ..................................................................... Apx A Tribal Funding Sources ........................................................................... Apx B Mitigation Strategy ................................................................................. Apx B Implementation of Tribal Mitigation Actions ............................................... Apx B Chapter 6: Plan Maintenance Strategy Adoption by Tribal Governing Body ...................................................................................... 116 Implementation .................................................................................................................... 116 Plan Monitoring & Evaluation ............................................................................................... 116 Plan Maintenance ................................................................................................................. 117 Distribution of Revisions ....................................................................................................... 118 Mitigation Measures and Project Close Outs ....................................................................... 118 Continued Public Involvement .............................................................................................. 119 Table of Contents/Introduction Page 5 APPENDICES A. Tribal Capability Assessment.......................................................... 120 Table 4.1 Chehalis Tribe Hazard Management Policies .............. 121 Hazard Management Plans and Capabilities ................................................ 124 Evaluation of the Tribe’s Policies Related to Development in Hazard Prone Areas .............................................................................................. 125 B. Mitigation Strategy- Tribal capacity assessment and tribal funding sources....................................................................................... 126 C. Mitigation strategy-Identification and analysis of tribal mitigation actions ....................................................................................... 126 D. Mitigation Measures ...................................................................... 127 Structural Mitigation Measures .................................................. 127 Table 4.2 Structural Mitigation Measures ……………………… 128 Mitigation Responsibilities and Timeframes............................. 129 Non-Structural Mitigation Measures ........................................... 131 Table 4.3 Non-Structural Mitigation Measures ............... 132 Non-Structural Mitigation Responsibilities and Timeframes ....... 132 Mitigation Funding Resources …………………………………………………………………………….134 BIBLIOGRAPHY ……………………………………………………………………………………………… 136 Table of Contents/Introduction Page 6 This page intentionally left blank. Table of Contents/Introduction Page 7 Chapter 1: INTRODUCTION The Confederated Tribes of the Chehalis Reservation (Chehalis Tribe or the Tribe) developed this Natural Hazards Mitigation Plan (NHMP) in accordance with the requirements of 44 CFR Part 201 and Section 322 of the DMA 2000, Federal Emergency Management Agency (FEMA). In addition, the Tribe has consulted technical guidance documents provided by FEMA and other agencies in the preparation of our NHMP. This plan is an update. The Chehalis Tribe previously participated in the 2004 Natural Hazards Mitigation Plan, Thurston Region. In this updated plan, the Chehalis Tribe sets forth specific analysis, identification and mitigation of hazards for the Chehalis Indian Reservation. Funding for the development of this plan was provided by the Chehalis Tribe and the Bureau of Indian Affairs, Indian Reservation Roads, Transportation Planning. The Chehalis NHMP was created to assist the Chehalis General Council and Business Committee, Tribal staff and Tribal community members plan for and reduce the human and economic losses and costs of flooding and other natural hazards and disasters. The Chehalis Reservation is located within a large floodplain and subject to minor flooding events up to five times annually. Flooding sufficient to limit access to the reservation, covering one or more reservation access roads, occur with a frequency of about every 2.6 years. Flood events up to and above 15 year frequency cover 75 percent of the reservation lands, with incremental encroachment on roads and homes. The development of a tribal NHMP is essentially to guide future efforts to effectively mitigate flooding and other natural hazards on the Chehalis Indian Reservation and, in coordination with other jurisdiction as appropriate, to mitigate and respond to natural hazards generated and adjacent to the Reservation or those that cross Reservation boundaries. The Comprehensive Emergency Management Plan (CEMP) is the ONLY governing document pertaining to governmental operations during Emergencies/Disasters; effective as of the end of March 2007, with the passing of Confederated Tribes of the Chehalis Reservation Resolution (CEMP; Appendix B; pg. 40.). All additional revisions will become effective once the Business Committee reviews and approves the revisions. This is the primary document for managing emergencies/disasters. Table of Contents/Introduction Page 8 For the Glossary of Terms, Comprehensive Emergency Management Plan (CEMP) See Chehalis CEMP, Appendix A, page 31. The Natural Hazards Mitigation Plan (NHMP) is a supporting document to the Tribal Comprehensive Emergency Management Plan (CEMP), will comply with all standards and guidelines established within, for example: 1. 1. 2. 3. Authority to Execute Plan Maintenance Review of the Base Document Appendices Change Process NOTE: The following PDM areas are classified as Appendices to this plan, and will comply with all criteria outlined with the Tribal CEMP pertaining to Appendices: A: Tribal Capability Assessment B: Mitigation Strategy 1-Tribal Capacity 2-Tribal funding C: Tribal Mitigation Actions D: Implementation of Tribal Mitigation Actions Table of Contents/Introduction Page 9 Chehalis Reservation Natural Hazard Mitigation Plan Chapter 2: PLANNING PROCESS This section describes how the plan was prepared, who was involved in the process, and how the public was involved. The Natural Hazard Mitigation Plan for the Thurston Region (2004) established multi-jurisdictional hazards for the region, including the Chehalis Indian Reservation. When the first plan was written, 44 CFR did not accommodate for Indian Tribe jurisdiction plans. With the amending of the CFR to include Indian tribal government plans, 207.1, the Confederated Tribes of the Chehalis Reservation (Chehalis Tribe or Tribe) declared their intention to develop a specific hazard plan for the Chehalis Indian Reservation. In May 2008, the Emergency Management Council of Thurston County sent a letter to 39 local stake holders to participate in the update of the Natural Hazards Mitigation Plan for the Thurston Region. A total of 26 jurisdictions actively participated in the plan update process including 18 of the original plan partners plus eight new participating jurisdictions. In Feb 2008, the Chehalis Tribe became aware of the 207.1 amendment to 44 CFR, allowing for Indian tribal government plans and made the decision to pursue development of a Reservation specific hazard plan under the individual tribal jurisdiction. Thurston Regional Planning Council, coordinator of the Thurston Regional Planning Process, was informed of the Tribe’s decision. The following table comprises the Hazard Mitigation Planning workgroup for the 2004 Natural Hazard Mitigation Plan. Table 1.1 Jurisdiction Adoption and Approval Dates of the 2003-2008 Natural Hazard Mitigation Plan for the Thurston Region Jurisdiction Adoption Approval Thurston County Town of Bucoda Town of Lacey City of Olympia City of Rainier City of Tenino City of Tumwater City of Yelm Confederated Tribes Of the Chehalis Reservation Fire District 4- Rainier August 4, 2003 May 24, 2005 September 11, 2003 December 9, 2003 March 2, 2005 July 22, 2003 July 15, 2003 August 13, 2003 July 19, 2003 October 3 2003 August 17, 2005 October 6, 2003 October 6, 2003 April 6, 2005 October 6, 2003 October 6, 2003 October 6, 2003 October 6, 2003 August 12, 2003 October 6, 2003 Chapter 2 Page 10 Chehalis Reservation Natural Hazard Mitigation Plan Fire District 9- McLane Fire District 13- Griffin Intercity Transit Providence St. Peter Hospital School District, North Thurston Public Schools School District, Olympia School District, Rainier School District, Tumwater School District, Yelm Community Schools The Evergreen State College August 14, 2003 August 14, 2003 June 2, 2004 May 6, 2004 January 18, 2005 August 9, 2004 June 12, 2003 November 28, 2004 July 9, 2003 October 6, 2003 October 6, 2003 October 6, 2003 August 25, 2004 February 28, 2005 October 6, 2003 October 6, 2003 October 6, 2003 December 23, 2004 October 6, 2003 Chehalis Tribe representatives for the 2004 workgroup were David Burnett, Tribal Chairman; Lennea Magnus, Planning Director and Ralph Wyman, Public Safety Director. This group also served as workgroup participants between 2003 and 2008. In March 2008, the Tribe recruited additional workgroup members to initiate the process of updating the plan and developing a Natural Hazards Mitigation Plan (NHMP) of specific to Confederated Tribes of the Chehalis Indian Reservation. Table 1.2 2008-2009 Hazard Mitigation Planning Workgroup for the Confederated Tribes of the Chehalis Reservation Name Position Jurisdiction/Agency David Burnett Chairman Lennea Magnus Planning Director Amy Loudermilk Transportation Planner Ralph Wyman Public Safety Director, Chief of Police, Emergency Services Coordinator Natural Resources Director Language Program Coordinator Communications, Newsletter Editor Tribal Elder Confederated Tribes of the Chehalis Reservation Confederated Tribes of the Chehalis Reservation Confederated Tribes of the Chehalis Reservation Confederated Tribes of the Chehalis Reservation Mark White Dan Penn Fred Shortman Catherine Barr Jill Kangus Anne Sullivan Mark Stewart Chapter 2 Emergency Manager Emergency Manager WA State Hazard Mitigation Officer Confederated Tribes of the Chehalis Reservation Confederated Tribes of the Chehalis Reservation Confederated Tribes of the Chehalis Reservation Confederated Tribes of the Chehalis Reservation Lewis County Grays Harbor County WA State Page 11 Chehalis Reservation Natural Hazard Mitigation Plan Diana Coho Kelly D. Cox Sophi Beym CFM, DHS-FEMA Mitigation Hazard Mitigation Officer VP Planning and Technology FEMA FEMA Tribal Emergency Management Systems, LLC PLAN UPDATE 2008-2009 The Regional Plan contained a large volume of material that was not specific to the Reservation culture, community or geography as it was a multi-jurisdictional plan covering a much larger region. The decision was made to rewrite the plan utilizing information very specific to the tribal culture and geographical location of the Chehalis Indian Reservation. The Committee’s role was to: participate in all aspects of the plan update process, meets as needed at the workgroup or within their department/agency to review, update and amend sections of the plan and coordinate comments from their department/agency, review, edit and/or commend on all elements of the draft and final plan. Chapter 1: Introduction was rewritten to clarify governing emergency documents for the Chehalis Tribe. Chapter 2: Planning Process was rewritten to update the material to reflect our current planning process and participants. Chapter 3: Thurston County Profile contained an overview of the greater Thurston County Region. Similar information providing an overview of tribal government, demographic and geography is now found in the Chapter 3 Chehalis Reservation Profile. Chapter 4: Risk Assessment consolidates the risk assessment and the hazard profiles into a single section. The four original hazard profiles included earthquake, flood, storm, and landslide. The Thurston County update contains flood, earthquake, severe storm, volcano and wildfire. In its update, Chehalis Tribe also added wildfire and volcano to its update. Landslide, however, was not included as the Chehalis Reservation is relatively flat, with no mountainous formations, hills, buttes or other threat of landslide. Analysis of structures, including transportation facilities, on the Chehalis Reservation was greatly increased and detailed. Chapter 2 Page 12 Chehalis Reservation Natural Hazard Mitigation Plan Chapter 5: Mitigation Initiatives were substantially modified in the update to the Chapter 5, titled MITIGATION STRATEGY-IDENTIFICATION AND ANALYSIS OF TRIBAL MITIGATION ACTIONS. Specific discussion of Thurston County staff processes, broad statements regarding regional and multi-jurisdictional activities were eliminated to reflect the mitigation planning and strategies specific to the Chehalis Indian Reservation. Discussion of abbreviations and formatting of the plan charts were also eliminated. The number and detail of mitigation strategies specific to the Chehalis Indian Reservation were greatly increased. Chapter 6: Monitoring, Implementation and Maintenance was also revised to reflect the plan’s focus on the Reservation community and to align with tribal procedures and protocols and were also revised to reflect current federal planning requirements. Annexes – The updated plan deleted the sections for multiple jurisdictions outside the Chehalis Reservation. Appendices were revised to serve the needs of the plan update. Chehalis Reservation Community Process The type and outcome of public meetings are as follows. Lennea Magnus, Planning Director for the Confederated Tribes of the Chehalis Reservation, hosted two community open forums. Seven hundred (700) advance notices were mailed out prior to the forums. The mailing list included all enrolled tribal members and nonIndian reservation households. During the public meetings participants were also interviewed one-on-one and were asked to complete a survey (below) identifying the most important natural hazards facing the community. They were also asked to comment on what the Tribe does right, when responding to emergency events, and what could be improved upon. Tribal members and residents had the following opportunities to comment prior to final approval. On June 4, 2008, two open public meetings were held, focused upon the primary natural hazard concerns of the community. Twelve Tribal members and reservation residents attended the first meeting and the second meeting was attended by (16) sixteen Tribal members and reservation residents. The residents were interviewed one-on-one focusing upon the most critical hazards facing the community. The community members commented on the tribal government response to emergency incidents and were asked for their opinion on emergency response improvements. In addition, tribal employees were encouraged to comment and share opinions. Next, research methods based upon guidelines from C.F.R. 44, 201.7 – Tribal Mitigation Plan directed the planning methodology. Comprehensive research conducted online and at the Learning Resource Center at the National Emergency Training Center in Emmitsburg, MD created the opportunity to gather additional resources in data, maps and journal articles. Input gathered from the Chehalis community meetings directed the selections for areas of interest. Each hazard or Chapter 2 Page 13 Chehalis Reservation Natural Hazard Mitigation Plan risk identified during the community meeting determined the mitigation priorities. The timeline to complete the plan is as follows: The Hazard Mitigation Plan was initiated in February of 2008 by the Chehalis Business Committee. They, in turn, directed the Tribal planning department to implement the project with a completion date of October 2008. The type and outcome of public meetings are as follows. Lennea Magnus, Planning Director for the Confederated Tribes of the Chehalis Reservation, hosted two community open forums. Seven hundred (700) advance notices were mailed out prior to the forums. The mailing list included all enrolled tribal members and nonIndian reservation households. During the public meetings participants were interviewed one-on-one and were asked to identify the most important natural hazards facing the community. They were also asked to comment on what the Tribe does right, when responding to emergency events, and what could be improved upon. Tribal members were involved in the planning process by using the Chehalis Tribal newsletter as the primary method of communication and were given the opportunity to review the plan in draft. Tribal residents received copies of the draft plan before the formal review team. They were encouraged to review the plan, and submit their comments to a local phone number. All comments by tribal members were included in the plan. The planning team initiated the process, developed the goals, objectives and timeline, assigned the lead agency and completed the introduction. They provided data to support the reservation profile; geography; and population demographics including languages, culture, history, household size, household characteristics, number of housing units, employment, median income, household income, poverty level, families below poverty, and education. Their contribution also included an overview of the tribal government structure and a comprehensive list of Tribal Land Use and Community Development Ordinances and Plans (1997 – 2008). This list consists of: (8) eight ordinances; (6) phases of the Facilities Master Plan; (1) one culture/historic report and (6) studies and plans for waste water, ground water assessment and long range transportation plans. Each person took personal responsibility to initiate the Natural Hazard Mitigation Plan, review the draft and actively provide comment(s) for accuracy and attention to detail. In addition, outreach to other entities was in the form of telephone conversations requesting a review of the draft. Technical research references Mitigation Plans from other counties; portions of those plans are included. The local county Emergency Managers were given notice of the upcoming document, expectations and due date. Outreach to U.S. Department of Homeland Security (DHS) - Federal Emergency Management Agency (FEMA) officials included telephone conversations to Kelly Cox, Hazard Mitigation Officer – Alaska, and email conversations with Diana Coho, FEMA, Certified Flood Manager (CFM) requesting preliminary review of Chapter 2 Page 14 Chehalis Reservation Natural Hazard Mitigation Plan the NHMP. Stakeholders had the opportunity to review, comment and guide the development of the plan. In addition to the public meetings, a community questionnaire was distributed with a response of 30 completed surveys. Chapter 2 Page 15 Chehalis Reservation Natural Hazard Mitigation Plan NATURAL HAZARDS PREPARNESS QUESTIONNAIRE RESULTS Total number of surveys = 30 Numbers highlighted in blue depict number of people answering. 1. In the past ten years have you or someone in your household experienced a natural disaster such as earthquake, severe winter storm or wind storm, flood, wildfire, or other type of natural disaster? 25 Yes 1.1 2. 83% 0 0% If “Yes”, what type of natural disaster has you or someone in your household experienced? Coastal Erosion Drought 0 1 0% 3% Dust Storm Earthquake 0 16 0% 53% Flood 26 87% Landslide Wildfire 4 0 13% 0% Household Fire Tsunami Volcanic Eruption Windstorm Winter Storm Other 9 0 30% 0% 2 21 7% 70% 18 60% 0 0% How concerned are you personally about each of the following natural disasters affecting the Chehalis Reservation? (1-very concerned, 5-not concerned) #1 3. No #2 #3 % #4 #5 Drought 0 0% 0 0% 3 10% 9 30% 15 50% Dust Storm Earthquake Flood Wildfire House Fire Volcanic Wind Storm Winter Storm Other 0 2 11 0 2 0 1 0 1 0% 7% 37% 0% 7% 0% 3% 0% 3% 0 5 9 4 6 3 11 13 0% 17% 30% 13% 20% 10% 37% 43% 0 12 5 9 8 1 8 9 0% 40% 17% 30% 27% 3% 27% 30% 0 8 2 8 8 8 5 5 0% 27% 7% 27% 27% 27% 17% 17% 30 0 0 8 4 16 3 1 0% 0% 0% 27% 13% 53% 10% 3% Have you ever received information about how to make your family and home safer from natural disasters? Chapter 2 Page 16 Chehalis Reservation Natural Hazard Mitigation Plan Yes 3.1 5 0 8 0 1 7& 40% 17% 0% 6‐12 mo 5‐more 6 0 .5 20% 0% 1‐2 yr 4 13% 27% 0% 3% Govt/Tribal Red Cross Other 2 2 1 7% 7% 3% Insurance Non‐profit 1 0 3% 0% Govt/Tribal Agency Utility Red Cross Not Sure 9 30% 4 13% 5 17% 1 3% 1 3% 19 7 16 2 63% 23% 53% 7% What is the most effective way for you to receive information about how to make your home and family safer from natural disasters? Newspaper Radio 6. 12 Who would you most trust to provide you with information about how to make your family and home safer from natural disasters? News Media Insurance University Non‐Profit Other 5. No From whom did you last receive information about how to make your family and home safer from natural disasters? News media Utility Co Not sure 4. 43% If “Yes”, how recently” Last 6 mo 2‐5 yr 3.2 13 12 7 40% 23% Television Other 9 22 30% 73% To help in communicating information to others about how to better prepare for a natural disaster, which phrase best describes how to prepare for a disaster? Natural Disaster Readiness 10 33% Emergency Preparedness 9 30% Disaster Preparedness Natural Hazards Risk Readiness 7 23% 1 3% In the following list, please check those activities that you HAVE DONE in your Chapter 2 Page 17 Chehalis Reservation Natural Hazard Mitigation Plan 8 household, PLAN TO DO in the near future, HAVE NOT DONE, or are UNABLE TO DO. A) Attended meetings or received written information on natural disaster or emergency preparedness. B) Talked with members in your household about what to do in case of a natural disaster or emergency? C) Developed a “Household/Family Emergency Plan” in order to decide what everyone would do in the event of a household emergency? D) Prepared a “Disaster Supply Kit” (stored extra food, water, batteries, or other emergency supplies)? E) In the last year, has anyone in your household train in the first aid or Cardio-Pulmonary Resuscitation (CPR)? 8A B C D E 9. Have Done % 7 23% 10 33% 4 13% 5 17% 17 57% Not Done 17 8 14 10 7 % 57% 27% 47% 33% 23% Unable To Do % 0 0 0 0 0 0% 0% 0% 0% 0% Building a disaster supply kit, receiving first aid training and developing a household/family emergency plan are inexpensive activities that require a personal time commitment. How much time (per year) are you willing to spend on preparing your household for a natural disaster or emergency event? 0‐1 hr 8‐15 hr 10. Plan to do % 4 36% 10 33% 11 37% 12 40% 4 13% 4 8 13% 27% 2‐3 hr 16+ 4 1 13% 3% 4‐7 hr Other 3 3 10% 10% What steps, if any, have your or someone in your household take to prepare for a natural disaster? Food Flashlight Battery Radio Smoke Det. First Aid/CPR Comm. Plan Other Chapter 2 12 19 10 21 16 4 2 40% 63% 33% 70% 53% 13% 7% Water Batteries First Aid Kit Disaster Kit Fire Escape Utility Shut Off 14 15 16 4 3 4 Page 18 47% 50% 53% 13% 10% 13% Chehalis Reservation Natural Hazard Mitigation Plan 11. Does your household have insurance coverage for earthquake events? 6 10 Yes Don’t Know 12. 16 37% 53% No 13 43% 17 2 57% 7% No 8 27% How much money are you willing to spend to better protect your family and home from natural disasters? $5000 15. 11 Would you be willing to spend more money on a home that had features that made it more disaster resistant? Yes N/A 14. No Did you consider the possible occurrence of a natural hazard when you bought/moved into your current home? Yes 13. 20% 33% = 1 3% $100‐499= 2 7% Other 3% = 1 $2500‐ 4999 = 2 $100‐1 = 3 7% 10% $1000‐ 2499 = 3 Nothing = 2 10% $500‐999 = 2 7% 7% Don’t Know =12 40% What nonstructural or structural modifications for earthquake have you made to your home? Anchor Latches Sec. Propane Other Sec. Home Br. Chimney None 4 4 2 2 8 2 14 16. Indicate your age. 17. Indicate your gender. Chapter 2 13% 13% 7% 7% 27% 7% 47% Secure Heater Flex. Conn. None 6 1 15 20% 3% 50% Brace Sheathing Brace Masonry Other 2 2 2 7% 7% 7% Median age of 35 Page 19 Chehalis Reservation Natural Hazard Mitigation Plan Male 18. 4 13% 20 67% Please indicate your level of education. 0 7 6 0 Grade School HS Grad/GED College Deg Other 19. Female 0% 23% 20% 0% Some HS Some College Post Degree 0 14 2 0% 47% 7% 4 4 13% 13% How long have you lived on the Chehalis Reservation? Less than 1 5‐9 years 20 years 0 4 14 0% 13% 47% 1‐5 years 10‐19 years 20. If you have lived on the Chehalis Reservation for less than 1 year, in what state did you live before your move to Chehalis. 21. Do you have access to the Internet or World Wide Web? Yes 22. 83% No 4 13% 63% No (rent) 9 30% No Apartment 3‐4 Manf. Home 0 0 6 0% 0% 20% Do you own your home? Yes 23. 25 19 Do you live in a single-family home? 17 57% Yes Duplex 4 13% Apartment 5 0 0% Other 1 3% Chapter 2 Page 20 Chehalis Reservation Natural Hazards Mitigation Plan Chapter 3: CHEHALIS RESERVATION PROFILE Tribal Government The Chehalis tribal governing body is the General Council, which is comprised of all enrolled members 18 years of age and older. The Business Committee, a fivemember body elected by the General Council for two-year terms, oversees tribal administration and business. The Business Committee is composed of the Tribal Chairman, Vice Chairman, Secretary, Treasurer, and Fifth Council Member. The tribe’s administrative functions are overseen by the general manager who reports directly to and receives policy direction from the Business Committee. The general manager oversees tribal operations through a departmental structure. The tribe’s organizational structure and management system promote a separation of policymaking and management functions, and establish clear lines of authority within the organization. The Chehalis Tribe provides a wide variety of public services to the community including Law Enforcement, Corrections, a Tribal court system, Medical/Dental Services, Head Start/Early Head Start, Elders meals and center, Vocational Rehabilitation, Education, Planning, Natural Resources, cultural and heritage programs and mental and behavioral health services including substance abuse counseling. Chapter 3 Page 21 Chehalis Reservation Natural Hazards Mitigation Plan A variety of federal and state grant and contract awards are administered throughout the tribal departments. During the most recently completed audit report, ending December 31, 2008, the Chehalis Tribe expended $30,237,359 on federal services and programs. Department of Interior (DOI) and Department of Health and Human Services (DHHS) encompass about 74% of revenues, with state and other federal grants and contracts contributing 26% of grant/contract revenues. Current grant awards being implemented include the following: two projects in IHS Special Diabetes Program for Indians, COPS Tribal Resources Program, ACF Indian Head Start/Early Head Start, Dept of Justice Indian Alcohol and Substance Abuse grant, Department of Education Indian Education and BIA Transportation Planning and Indian Reservation Roads Construction. The Chehalis Tribe operates several successful entertainment enterprises including the Great Wolf Lodge Resort, a 400 room hotel, convention center and indoor water park; the Lucky Eagle Casino, 106,000 sq ft casino and Eagles Landing Hotel, a 70room hotel. The Tribe also owns and operates three convenience stores, two with a gas station; a cigarette stamping business and two construction companies. The Lucky Eagle Casino is very successful and has been in operation since 1996. The Chehalis Tribe opened the Great Wolf Lodge in 2008. The Chehalis Tribe has a total of 1,498 employees. Table 2 Chehalis Tribe Employees Chehalis Tribe Employees Chehalis Tribal Administration and Services 143 Lucky Eagle Casino 667 Great Wolf Lodge 593 Eagle’s Landing Hotel 24 Chehalis Tribal Enterprises 71 Total tribal employment 2009 1,498 Source: Chehalis Tribe Human Resources Department, Feb. 2009 Chapter 3 Page 22 Chehalis Reservation Natural Hazards Mitigation Plan Statistical Profile: Confederated Tribes of the Chehalis Reservation Population, 1990 ----------------------------- 491 Population, 2000 ----------------------------- 691 Average Annual Population Growth ----------- 3.5% Tribal Enrollment 2000------------------------- 629 Tribal Enrollment 2009------------------------- 828 Service Population, 2000 ------------------ 2,143 Service Population, 2006 ------------------ 3,453 Households, 2000 ---------------------------- 194 Average Household Size, 2000 ---------------- 3.56 19 and under ------------------------------303 _______ 44% 20 - 64 ------------------------------------- 347 ________ 50% 65 and over --------------------------------- 41 ________ 6% Median Age --------------------------------- 25 Race and Ethnic Categories, 2000: White --------------------------------------- 239 32.2% Black/African American --------------------- 3 0.4% American Indian & Alaska Native ------------------------------ 388 52.2% Asian ------------------------------------------0 0.0% Native Hawaiian & Other Pacific Islander ----------------------- 0 0.0% Other Race ---------------------------------- 12 1.6% Two or More Races ------------------------- 49 6.6% Hispanic* ----------------------------------- 52 7.0% Housing Units, 2000 Single-Family ------------------------------ 139 Multifamily ---------------------------------- 25 Manufactured Homes ---------------------- 51 Median Household Income 1989 (Census 1009 in 1999 $’s) -----$18,556 1999 (Census 2000) ------------------ $30,000 Explanation: *Person of Hispanic Origin can be of any race Source: Thurston Regional Planning Council, Profile 2009 Socio-Economic Figures from the 2000 U.S. Census confirm the Chehalis Reservation population of 691 persons. This is an increase of 41% over the 1990 U.S. Census. In direct comparison, Grays Harbor County population increased a mere 4.7%, Thurston County population increased 28.6%, and Washington State American Indian/Alaska Native populations increased 29%. According to The U.S. Bureau of Indian Affairs, U.S. Labor Force Report, 2006 there are 728 enrolled members of the Chehalis Tribe. The same report accounts for a service population of 3,453; a service population is defined as “enrolled and non-enrolled Native Americans living on and near the Reservation and non-Native American with familial or economic ties to the Reservation and receiving services”. Census 2000 data indicate a majority of the Chapter 3 Page 23 Chehalis Reservation Natural Hazards Mitigation Plan population, approximately 44%, under the age of 19, with a median age of 24.5 years. By contrast, Grays Harbor County has a median age of 36.8 and Thurston County a median age of 36.5. Tribal Lands The Chehalis Reservation is located in southwestern Washington State in a river valley formed by the confluence of the Black River and the Chehalis River. The Reservation is approximately 5,000 acres in size and consists of agricultural areas, residential neighborhoods and forested stands. The mountains of Capitol Forest and the Doty Hills to the north border the valley. The current and historical paths taken by the Chehalis and Black rivers dominate the Chehalis Reservation. The current river channels within the Reservation contain approximately (10) ten miles of the Chehalis River and the principal fish harvested are Spring Chinook Salmon, Coho Salmon, Fall Chum Salmon, Fall/Summer Chinook Salmon and Winter Steelhead. Historically surrounded by thick forests, the Chehalis Reservation currently has over 2,700 acres of forested stands. There are many stands of White Oak and Douglas Fir as well as riparian areas consisting of a mixture of Western Red Cedar, Big Leaf Maple, Cottonwoods and Alder trees. Many of the stands are second growth populations due to the heavy logging that occurred here within the past 100 years. The regular flooding of the rivers has created fertile soils in the valley. The rich soils combined with the long growing season provide a productive agriculture zone. Agriculture became prevalent in the valley and on the Reservation once European settlers moved to the area in the late 1800s. At the peak of farming activities on the Reservation, there were approximately 1,100 acres of land used for raising crops like hay or alfalfa or pasturelands for livestock. The large quantity of wetlands, riparian areas and water features along with unique land features such as acres of natural prairie lands, provide habitat for a great variety of flora and fauna. Some of the major animal species found in the area include: elk from the Olympic Elk Herd, white-tailed deer, river otter, opossum, raccoon, bald eagle, great blue heron, kingfisher and approximately (3) three miles of the Black River, upstream from the mouth of the river. Many wetlands, sloughs and oxbow ponds are remnants of old river channels. Tribal members utilize the river in many ways but primarily for harvesting salmon in customary fishing sites. Unique flora found on the Reservation includes camas, shooting stars, wild strawberries and white oak. Since the adoption of the Chehalis Comprehensive Plan, 2004, the Tribe has pursued a policy of purchasing farmland located primarily on the floodplain for conservation purposes including reforestation, wildlife habitat and wetlands development. Chapter 3 Page 24 Chehalis Reservation Natural Hazards Mitigation Plan Historic/Traditions/Culture Historically, the indigenous population of the Chehalis originally occupied a specific geography within the Chehalis watershed. This watershed encompasses a region from the foothills of the Cascade mountain range to the Pacific Ocean in the southwest region of the state of Washington. “Chehalis” is a collective name for several Shalishan Tribes living on the Chehalis River, its affluent, and in Grays Harbor. The Chehalis people have lived on a reservation since the 1850s; however, important archaeological, cultural, and historic sites are scattered throughout the original indigenous geography. The Chehalis Tribe did not sign a treaty but in 1864, by executive order, land was set aside for the Chehalis reservation. In 1939, the Confederated Tribes of the Chehalis reservation was formed and approved by the federal government and its Constitution was amended in 1973 (Chehalis). “In the old days we gathered sacred roots and berries. We fished the Chehalis, Black, Cowlitz, Satsop, Wynoochee, Elk, Johns, Skookumchuck and Newaumkum rivers. Our people fished and hunted from the mountains, across the prairie, to Grays Harbor and the lower Puget Sound. In the old days, the baskets carried and stored our foods. We relied upon the baskets, the rivers, the land, the roots, the berries, the fish, and the animals. Our lives were tied together by the Creator” (Bellon, Francis and Hicks). At one time, there were many villiages in the Upper Chehalis region, principal ones being located in the Upper Chehalis region, principal ones being located at the mouths of rivers and creeks. Elders of the Tribe have identified major village sites as they remembered from years previous, including the mouths of Lincoln Creek, Scatter Creek, Skookumchuck River, Black River, Cedar Creek and at Grand Mound. A very large settlement once stood at Grand Mound; its name was ‘aqáygt, meaning “long prarie”. About a mile above the mouth of the Skookumchuck was a village called ‘tè·’wt’n, meaning “fording place”. Where the Black River enters the Chehalis near Oakville there was a village called s ‘àc l’t, or “made lake”. Continuing down river, there were villages at the mouth of Cedar Creek and below Porter. Near Malone was ‘nsxà·wm or “carrot place” indicating a place where wild carrots were plentiful (Bellon, Francis and Hicks). Within the village lived one or more extended families or “house groups”, each occupying it’s own large (from 80-100 feet long) house constructed from cedar planks. The house group included a headman, his wives and relatives, and may have included some slaves, either captured or traded from other Tribes. Each family within the longhouse had its own fire, and cattail mats were often hung as partitions. Around the inside walls of the house was a double row of cedar platforms used for sleeping and sitting, covered with several thicknesses of mats. Above the platforms were shelves for storing household goods and provisions. Smoke left the building through a hole in the roof covered with a hinged board that could be opened or closed with a pole. Unlike Puget Sound, where the houses had shed-type roofs, the Chehalis house had a gabled roof and verticle wall boards. During the summer months when the house was not lived in, the boards were lowered and fresh air let in (Bellon, Francis and Hicks). Gaining a livlihood from the resources of the land and waters demanded adjustment to seasonal patterns. Chapter 3 Page 25 Chehalis Reservation Natural Hazards Mitigation Plan The Upper Chehalis like all tribes in the area, followed the natural cycle of the flora and fauna of their territory and moved about a great deal during the course of the year to collect certain kinds of foods. Various species of fish were caught at certain places. Elk hunting took place when travel in the mountains was easiest. Large quantities of fish, meat, roots and berries were dried or smoked, then stored inside the longhouse. Women gathered and prepared all the vegetable foods. Camas bulbs, roots of bracken fern, wild sunflower, wild carrots, acorns, and hazelnuts formed a part of the Chehalis diet. Berry picking was an important activity during summer months. Entire families might camp at the berry-picking grounds, the women and children picking and preparing the fruit while the men went to fish, hunt and compete in horse races. This was a time that people looked forward to, a chance to meet friends and relatives and to enjoy games and feasting when the work was complete (Bellon, Francis and Hicks). In order to encourage the growth of berries and camas, the Upper Chehalis would burn the prarie lands every two or three years. In this way they were assured of a good suppply in those areas. Such resource areas were not used exclusively by one village but rather shared by serveral villages and even among people of different tribes. Fishing occupied the men beginning in late spring and ending in late fall. Four kinds of salmon, (Chinook, pink, silver and dog) as well as steel head frequented the waters of the Upper Chehalis territory. Small fish like suckers and trout could be caught year round. Eels migrate up the Chehalis River in late spring and at Rainbow Falls, caught on the rocks as they attemped to assend. In June, eels could be found also in Lincoln Creek just before the fishing began in the Skookumchuck. The resources of nearby salt-water areas supplemented the diet of the Upper Chehalis; they went up the Black River to Mud Bay to gather clams and to catch flounder. The Upper Chehalis used a combination of spears, hooks, nets, traps and weirs to obtain their year’s supply of salmon. Members of two or more families shared in the catch. When one group had caught enough for its needs, another group came and fished the site. Spears and gaff hooks were essential fishing gear throughout this area. The spear was generally used in shallow water or at traps and weirs, the hooks in deeper water. The Upper Chehalis used a variety of nets, including seine nets, tubular nets and dip nets. A strong reliance on fish in the subsistence economy of the Upper Chehalis is typical of a river people, but they also relied heavily on deer, elk and smaller game that frequented their terriroty. When an elk was killed, the hunting party butchered and dried the meat before packing it all the way to the villiage. The successful hunter gave a feast at which he shared the elk meat with his friends and relatives. Elk tallow was used like butter on dried fish and meat, and also rubbed on the face to prevent chapping. Chapter 3 Page 26 Chehalis Reservation Natural Hazards Mitigation Plan Chapter 4: RISK ASSESSMENT Risk Assessment Introduction The Confederated Tribes of the Chehalis Reservation (Chehalis Tribe) developed this plan to meet the requirements of C.F.R.44, 201.7, Tribal Mitigation Plan. More importantly, the plan was created to reduce future loss of life, land and property due to natural hazards that affect the Tribe. It is difficult to predict when natural hazards will affect the Reservation; however, it is accurate to say they will. The Chehalis Tribe is a small, tightly knit community. The Tribe, Tribal community, contractors, Tribal employees, and others worked closely together to assess create this risk assessment. The largest and most costly disasters to occur in the area of the Reservation have been floods. The most recent disaster occurred in December of 2007. The Reservation faces many natural and manmade hazards. Although some are on a seemingly small scale, they often prove disabling to the Reservation community. During one of the community meetings, tribal members were invited to list all the possible hazards that they thought might impact the community. Work group members were also invited to list all potential hazards that they believed could possibly occur. The hazards listed are the result of these brainstorming sessions. Once listed, the work group ranked the probably of occurrence, vulnerability of the community and overall risk rating. Table 3.1 Hazard/Risk Rating Hazard Probability of Occurrence Flooding High Earthquake High Severe Storm High Volcano Low Wildfire High Drought Medium Landslide Low Tsunami Low Vulnerability Overall Risk Rating High High High High Low High Medium Low High High High Medium Medium Medium Medium Low Risk Rating: and adjective description (High, Medium, or Low) of the overall threat posed by a hazard is assessed for the next 25 years. Risk is the subjective estimate of the combination of a given hazard’s probability of occurrence and the reservation’s vulnerability to the hazard. Chapter 4 Page 27 Chehalis Reservation Natural Hazards Mitigation Plan • High: There is a strong potential for a disaster of major proportions during the next 25 years; or history suggests the occurrence of multiple disasters of moderate proportions during the next 25 years. • Medium: There is a medium or moderate potential for a disaster of less than major proportions during the next 25 years. • Low: there is little potential for a disaster during the next 25 years. Probability of Occurrence: An adjective description (High, Medium, Low) of the probability of a hazard impacting the Chehalis Reservation within the next 25 years. • High: there is great likelihood that a hazardous event will occur within the next 25 years. • Medium: There is a medium likelihood that a hazardous event will occur within the next 25 years. • Low: There is little likelihood that a hazardous event will occur within the next 25 years. Vulnerability: Vulnerability can be expressed as a combination of the severity of a natural hazard’s effect and its consequential impacts to the community. An adjective description (High, Medium, Low) of the potential impact a hazard could have on the Chehalis Reservation. It considers the population, property, commerce, infrastructure and services as risk relative to the surround region and counties. • High: The total population, property, commerce, infrastructure and services of the reservation that are uniformly exposed to the effects of a hazard of potentially great magnitude. In a worst case scenario, there could be a disaster of major to catastrophic proportions. • Medium: The total population, property commerce, infrastructure and services of the reservation that are exposed to the effects of a hazard of moderate influence; or the total population, property, commerce, infrastructure and services of the reservation are exposed to the effects of a hazard of moderate influence, but not all to the same degree; or an important segment of the total population, property, commerce, infrastructure and services of the reservation are exposed to the effects of the hazard. In a worst case scenario, there could be a disaster of moderate to major, though not catastrophic, proportions. • Low: A limited area or segment of the population, property, commerce, infrastructure and services of the reservation is exposed to the effect of a hazard. In a worst case scenario, there could be a disaster of minor to moderate proportions. The following hazards were identified for further study: 1. 2. Flood Earthquake Chapter 4 Page 28 Chehalis Reservation Natural Hazards Mitigation Plan 3. 4. 5. Severe Winter Storm Volcano Wildfire The hazards selected for study were identified as most likely to occur, based on reservation history and experience and are of the most concern to community residents. All hazards with a “high” probability of occurrence – Flooding, Earthquake, Severe Storm and Wildfire were selected for study. Volcano was also selected as the reservation is within 75 of Mount St. Helens which has erupted several times in the past 30 years. While the likelihood of eruption is “medium”, the vulnerability of the reservation is considered “high” as the pyroclastic eruptions of this volcano are likely to reach the reservation and particularly detrimental and harmful to mechanical and electrical equipment. Pyroclastic or ash eruption also carries heightened health risk for persons with certain medical conditions which are prevalent on the reservation. RISK ASSESSMENT Above map of flood affected areas, December 2007 incident. Chapter 4 Page 29 Chehalis Reservation Natural Hazards Mitigation Plan P’ucú­ (Kinkade) Flood The Great Spirit, angry about the wickedness of people and animals, decided to rid the earth of all but the good animals, one good man, and his family. At the Great Spirit's direction, the man shot an arrow into a cloud, then another arrow into that arrow, and so on, making a rope of arrows from the cloud to the ground. The good animals and people climbed up. Bad animals and snakes started to climb up, but the man broke off the rope. Then the Great Spirit caused many days of rain, flooding up to the snow line of Takhoma (Mount Rainer). After all the bad people and animals drowned, the Great Spirit stopped the rain, the waters slowly dropped, and the good people and animals climbed down. To this day, there are no snakes on Takhoma. [Clark, pp. 31-32] Once a big flood came, people made ropes of twisted cedar limbs and used them to fasten their canoes to mountains. The flood covered the Olympic Mountains. Some of the ropes broke, and the canoes drifted to the country of the Flatheads. That is why the Skokomish and the Flatheads speak the same language. [Clark, p. 44] (Clark 44) http://blog.americanrivers.org/wordpress/index.php/2007/12/06/lessons‐from‐flooding‐in‐the‐pacific‐ northwest/ Definitions Cfs = Cubic Feet per Second NWS = National Weather Service Flood stage is the elevation of a river’s surface at a gauging station, determined by NWS, at which overflow of the natural banks of a river begins to cause damage in the local area by flooding. Flow is the amount of water flowing in a river past the gauging station, usually stated in cubic feet per second - sometimes called stream flow or discharge. Gage height is the elevation of a river’s surface at a gauging station, in reference to an established elevation point – sometimes called stage. (USGS) PROBABILITY Grays Harbor County is the most vulnerable county to floods in Washington State (Washington State Hazard Mitigation Plan, 2004, Tab 7.1.4 – p. 17) and floods are the most common natural disaster to occur in the County. The frequency of a moderate or higher flood event in the County from 1956 to 2004 was every three years. Recent studies have identified the frequency and peak flows of floods have increased since 1990. The probability of future flooding, based on long-term trends, can be assumed to be at least once every three years. The probability could be higher if present trends continue given there were seven major floods from 1990 to 2003 included in Federal Disaster Declarations. The cause of flooding in Grays Harbor County is a combination of climate, topography, and land development. A predominately marine climate with mild wet winters dictates weather patterns in the County. Flood season usually begins in early November when heavy rainfall occurs. Pacific frontal systems become stationary over the region, bringing long periods of rainfall through February and often extending into March. Chapter 4 Page 30 Chehalis Reservation Natural Hazards Mitigation Plan Annual precipitation is 65” to 75” on the coast, 80” to 90”near the foothills, 125” to 150” on the windward slopes of the Olympic Mountains, and 100” for the Willapa Hills. During long periods of rainfall, river and stream channels fill to overflowing. Intense precipitation combined with mild temperatures will cause snowmelt on the south slopes of the Olympic Mountains which can also induce or increase flooding. Extensive floodplains and wetlands contribute to the regional nature of flood events in the County. River floods happen most often when winter storms bring heavy rains from the southwest. The heavy precipitation causes the main river or stream channel’s flood capacity to be exceeded. The effect of this is overflowing rivers and streams allowing water to flow from the floodway onto the floodplain. The Chehalis River, a dominant factor in floods in the County, meanders east to west along a broad, flat river valley terminating in Grays Harbor. The largest tributaries of the Chehalis are the Satsop and Wynoochee Rivers originating on mountain slopes north of the river. The Chehalis River Basin is the second largest river basin in the state of Washington outside the Columbia River Basin. The total drainage area of the Chehalis River Basin is 2,660 square miles of which approximately 85% is forest lands. Approximately 257 square miles (164,000 acres), or 9.7% of the basin is agricultural land. Approximately 75 percent of the Chehalis Reservation is located in the drainage of the Chehalis River Basin, creating an active floodplain that is subject to minor levels of flooding annually, with moderate or higher flooding occurring every three years. In the last three decades, the Chehalis Reservation has experienced several very large floods, including the 1986, 1990, 1996 and 2007 floods, each of which ranked as a flood of record at the time of its occurrence. Flooding within the Chehalis Reservation restricts access to the Reservation for periods of one or more days, isolating portions of the Reservation, and may cause failure of individual water and waste water systems. Flooding of Chehalis Reservation lands requires immediate evacuation of non-residents, invacuation of residents (that is, keeping people within a building or other location while a dangerous situation exists outside the building or location), and severely limits access to basic goods and services. Severe flooding also can contribute to the formation of swift-moving water in floodways that is capable of significantly endangering residents and their property. Flooding of this type can affect more than two-thirds of the Chehalis Reservation. The consequences of floods within the Chehalis Reservation have been very costly in terms of human life, property and economic health. Significant damage has occurred to public and private investments, interrupted public services and schools and closed businesses. Flooding from 15-year and greater recurrence interval storms is severe, and endangers roads and many structures within the floodplain. (Chehalis Comprehensive Flood Hazard management Plan, 2009) Typically, high water levels occur between November and February. Moderate flooding occurs when the flow rate exceeds about 26,000 cfs. Since 1972, this has occurred more than 20 times. Major flooding occurs when the rate exceeds about Chapter 4 Page 31 Chehalis Reservation Natural Hazards Mitigation Plan 50,000 cfs. This has happened six times since 1972. In February 1996, the record flow rate was 75,000 cfs. The Black River is a slow, meandering stream that flows through Thurston County for approximately 19 miles. Extending from Black Lake, marshland lines the river and the water table is perennially at or above the ground surface. Back-flow from the Chehalis River causes the preponderance of flooding along the Black River and similar recurrence intervals are expected. The reservation, because of the relative land area and population affected, is exposed to high vulnerability. The frequency of flooding, the potential for simultaneous flooding events, involving both the Black and Chehalis rivers, plus the historical record of recurrent flooding and cumulative costs, all suggest the assignment of a high-risk rating. (Thurston County IV-26). Probability, likelihood and frequency of flood incidents in Chehalis Reservation are high, with moderate to severe intensity. The histories of floods are as follows: A review of USGS flood gauge data shows that over a 37 year period, 1970-2008, there have been twelve major flood events on the Chehalis Reservation. Since 1990, seven major flood events have occurred. Table 3.2 Historical Flood Events Table Historical Flood Events Flood Gage @ Centralia December 2007 74.78 KCSF* 74.31 73.5 72.4 71.99 71.65 71.3 71.17 70.2 Flood Gage @ Grand Mound 20.23 KCFS* 19.98 19.34 18.18 18.41 18.21 18.12 17.73 February 1996 January 1990 January 2009 November 1986 January 1972 November 1990 December 1975 January 1971 April 1991 17.66 December 1996 70.18 February 1990 69.91 17.46 *KCFS (Thousands of Cubic Feet Per Second) for a particular stage at that river location A Recent flood event, December 4, 2007, set a new record in peak stream flow in the upper watershed of the Chehalis River. The stream flow indicates a pattern resulting from a very intense rainstorm, according to the U.S. Geological Survey. Peak stream flow was recorded at 51,100cfs before floodwater swamped the instruments and destroyed equipment at Doty, WA. The previous record peak flow recorded at Doty was 28,900 cfs during the February 1996 flood. (USGS) Chapter 4 Page 32 Chehalis Reservation Natural Hazards Mitigation Plan (USGS, Chehalis Basin) Thurston County in its Natural Hazards Mitigation Plan, September 2009, Table 4.3.4, notes the following probability of Chehalis River flooding as follows: Flood Severity Events 1968 to 2009 Annual Probability Rate of Occurrence (years) Minor 62 151/2% .7 Moderate 23 56.1% 1.8 Major 9 22.0% 4.6 Chapter 4 Page 33 Chehalis Reservation Natural Hazards Mitigation Plan Identification and Profile Floods cause loss of life and damage to structures, crops, land, flood control structures, roads and utilities. Floods also cause erosion and landslides and can transport debris and toxic products that cause secondary damage. Flood damage in Washington State exceeds damage by all other natural hazards. There have been 28 Presidential Major Disaster Declarations for floods in Washington State for flooding since 1970. While not every flood creates enough damage to merit such a declaration, most are severe enough to warrant intervention by authorities. Since 1980, to repair public facilities, help individuals recover from flood disasters and pay measure to prevent future flood damage required a $522 million dollar investment. That is nearly 40% of the $1.37 billion dollar amount spent on disaster relief and hazard mitigation during this time. The magnitude of most floods in Washington depend on particular combinations of intensity and duration of rainfall, pre-existing soil conditions (i.e. was ground wet or frozen before the storm), area of basin, elevation of rain or snow level and amount of snow pack. Synthetic changes to a basin can also affect the size of floods. (Pudlo 7.1.4 p1) A flood is a general or temporary condition of partial or complete inundation of normally dry land areas from (1) overflow of inland or tidal waters (2) the unusual and rapid accumulation of runoff or surface waters from any source, or (3) mud flows or the collapse of shoreline land. (County 77) Several factors determine the severity of floods, including rainfall intensity (or other water source) and duration. A large amount of rainfall over a short time span can result in flash flood conditions. In locations where soil is saturated from a previous wet period or if rain is concentrated in an area of impermeable surfaces, such as a large parking lot, paved roadway or other impervious developed area, a small amount of rain can also result in floods. Topography and ground cover are also contributing factors for floods. Water run-off is greater in areas with steep slopes and little or no vegetative ground cover. The frequency of inundation is affected by climate, soil and channel slope. Characteristics of Flooding 1. Stationary frontal systems 2. Heavy precipitation 3. Increasing frequency of events 4. Saturated soils 5. Erosion 6. Flooding in association with another hazard event Types of flooding common in the Chehalis area are: 1. River or stream building floods, 2. Flash floods, 3. Groundwater flooding River and stream building floods occur because of prolonged heavy rainfall, a rapidly melting snow pack or a combination of these. According to the Natural Hazards Mitigation Plan for Thurston County, “historically, Thurston County must Chapter 4 Page 34 Chehalis Reservation Natural Hazards Mitigation Plan experience two or three days of rainfall averaging 2-5 inches per day for this type of flooding to occur”. (T. County IV-21) The Chehalis River has flooded because of events in their watersheds outside of the reservation. River floods happen most often when winter storms bring heavy rains from the southwest. Heavy precipitation events occur when water exceeds the main river or stream channel’s flood capacity. The effect of this is over flooding rivers and streams allowing water to flow from the floodway onto the floodplain. In addition, solid saturated with moisture will weaken and destabilize banks contributing to more flooding and erosion. The Chehalis River, a dominant factor in floods, meanders east to west along a broad, flat river valley terminating in Grays Harbor. The largest tributaries of the Chehalis are the Satsop and Wynoochee Rivers originating on the mountain slopes north of the river. River and stream building floods are the most common because of many river and stream and development patterns along them. (T. County IV-21) There are three types of river flooding: 1. Nuisance/Minor flooding: The River exceeds bank-full conditions at one or more locations, generally flooding fields and forests. Some roads may be covered but passable. There may be enhanced erosion of some riverbanks. 2. Moderate flooding: Individual residential structures are threatened and evacuation recommended for selected properties. Some roads may be closed. Moderate damage may be experienced. 3. Major flooding: For neighborhood and community residents living on specific areas along the river the risk is higher and evacuation recommended. Major through fares may be closed and major damage is expected A flash flood is a quick rise and fall of water level. Flash floods generally result from intense storms dropping large amounts of rain within a short period onto watersheds that cannot absorb or slow the flood. The natural terrain and vegetation of the Chehalis reservation help to reduce the potential for flash floods. As development continues, increasing the distribution and proportion of impervious surfaces, the threat from flash floods will increase. (T. County IC-22) Ground water flooding occurs when there is a high water table and persistent heavy rains. An upper, thin layer of permeable soils overlaying an impermeable layer of hardpan causes this situation. As the ground absorbs more and more rainwater, the groundwater table rises and shows itself as flooding in areas where the land surface is below the water table. The conditions have historically been most severe in the second and subsequent years of consecutive wet years. According to the Army Corps of Engineers, the frequency of a groundwater flooding disaster is every 25 years. (T. County IV-22) FEMA has mapped most of the known floodplains in the United States. The Chehalis River extends for only 8.6 miles in Thurston County has an extensive floodplain, covering over (8) eight square miles. Land use is primarily agriculture, houses are scattered sparsely over the area. Some flooding occurs nearly every Chapter 4 Page 35 Chehalis Reservation Natural Hazards Mitigation Plan year, but damage is usually light. Historically, minor/nuisance flooding occurs when the flow rate exceeds about 14,000 cfs. Since 1972, the river has exceeded the flow rate 48 times. Groundwater has historically been most severe in the second and subsequent years of consecutive wet years. According to the U.S. Army Corps of Engineers (“Corps”) post even report on the storm of 1996-97, the frequency of groundwater flooding disaster is every 25 years. This was the first widespread flooding disaster event since 1972 and the worst on record until the winter of 1996, which was considered the “event of record” until December 2007. The 2007 event set a new record in peak stream flow in the upper watershed of the Chehalis River. The stream flow indicates a pattern resulting from a very intense rainstorm, according to the U.S. Geological Survey. Peak stream flow was recorded at 51,100 cfs before floodwaters swamped the instruments and destroyed equipment at Doty, WA. The previous record of peak stream flow recorded at Doty was 28,900 cfs during the February 1996 floor. (USGS) Statistically, the Corps estimates there is approximately a 70% chance that the 1996-97 flooding will be equaled or exceeded at least once during a 30-year mortgage cycle. According to FEMA records for the March 1997 high groundwater flood event, only 15 of 237 damage sites (6%) occurred within the mapped 100year floodplain. When added together, the 100- and 500- year floodplains it increased to 9%. (T. County IV-24) Flood – Historic Profile Data gathered from the United States Geological Survey (USGS); NWS; Thurston County; Grays Harbor and Washington State Mitigation plans created this section of the NHMP. The data limitations were few. Technical data in the form of real-time surface water sites are available for download from the USGS website. The following chart indicates real-time surface-water sites monitored by the USGS. Identification No: 12027500 is Chehalis River near Grand Mound, WA and Identification No: 12025100 is Chehalis River at Centralia. USGS river gauging stations form the backbone of flood-warning systems in the state. Federal agencies such as the Corps of Engineers and the NWS and others, use the real-time stream flow data from USGS river gauging stations to monitor the rivers closely to protect people and property. (Clemen) Chapter 4 Page 36 Chehalis Reservation Natural Hazards Mitigation Plan (FEMA, Debris after Washington Flood) Table 3.3 USGS Advanced Hydrologic Prediction Service: Seattle, Chehalis River near Grand Mound, Flood Categories (in feet) (USGS) Major Flood Stage Moderate Flood Stage Flood Stage Action Stage 17 15.5 14 12.2 Historical Crests 20.23 feet 19.98 feet 19.34 feet 18.41 feet 18.39 feet 12/04/2007 02/09/1996 01/10/1990 11/25/1986 12/29/1937 Flood Impacts (Chehalis River near Grand Mound): At 19.0 feet, the Chehalis River will cause severe near record flooding, with deep and swift floodwaters inundating the Independence Valley. Flooding will occur all along the river including headwaters, tributaries and other streams within and near the Chehalis River Basin. Chapter 4 Page 37 Chehalis Reservation Natural Hazards Mitigation Plan At 17.5 feet, the Chehalis River will cause major flooding, inundating roads and farmlands in Independence Valley. Deep and swift floodwaters will cover SR-12 and Independence and Moon Roads. Flooding will occur all along the river including headwaters, tributaries, and other streams within and near the Chehalis River Basin. At 15.5 feet, the Chehalis River will flood several roads in Independence Valley with swiftly moving water including SR-12 and James, Independence, Moon and Anderson Roads. Floodwaters will cut off access to and from Chehalis reservation and inundate nearby farmlands and some residential structures may be threatened. At 14.0 feet, the Chehalis River will flood several roads in Independence Valley including James Road, Independence Road and Moon Road. Floodwaters will also cover nearby farmlands At 12.5 feet, the Chehalis River will locally spill out of its banks into nearby fields and over a few roads. (USGS) Table 3.4 USGS Advanced Hydrologic Prediction Service: Seattle, Chehalis River at Centralia Flood Categories (in feet) Major Flood Stage 72 Moderate Flood Stage 68.5 Flood Stage 65 Action Stage 61 Historical Crests 72.78 feet 74.31 feet 73.5 feet 71.99 feet 71.65 feet 12/04/2007 02/09/1996 01/10/1990 11/25/1986 01/21/1972 Flood Impacts (Chehalis River at Centralia): At 73.4 feet, the Chehalis River will cause severe near record flooding with deep swift floodwaters inundating residential and business areas, roads including I-5 and farms. Flooding will occur all along the river including headwaters, tributaries and other streams within and near the Chehalis River Basin. At 72.0 feet, the Chehalis River will cause major flooding inundating residential and commercial areas, farms and many roads including I-5. Floodwaters will be deep and swift in some areas. Flooding will occur all along the river including headwaters, tributaries and other streams within and near the Chehalis River Basin. At 68.5 feet, the Chehalis River will flood some residential and commercial areas with water encroaching upon the first floor of some homes and businesses. Swift floodwaters will cover some roads. At 65.0 feet, the Chehalis River will cause shallow flooding of farmlands and some roads. Chapter 4 Page 38 Chehalis Reservation Natural Hazards Mitigation Plan At 53 feet, the Chehalis River will spill over its banks into nearby pasturelands around Chehalis and Centralia. (FEMA, Road Damage from Washington Floods) Chapter 4 Page 39 Chehalis Reservation Natural Hazards Mitigation Plan Topography Geological formations determine the topology of the Chehalis reservation. The geological map show older terraces forming “islands” of higher ground surrounded by alluvial floodplain. The higher terraces are 10 – 20 feet above surrounding lands and are the only areas of the reservation that do not flood. The reservation land has an elevation of up to 115 feet above mean sea level on the highest eastern terrace. The surrounding floodplains average around 95 feet. The elevations drop on the western end of the reservation corresponding to the fall in the Chehalis River. The western terrace averages about 88 feet in elevation while the floodplains near the river, average about 70 feet. With the exception of a few relatively steep escarpments between the terraces and the floodplain, the land slopes at a very gradual rate. Chapter 4 Page 40 Chehalis Reservation Natural Hazards Mitigation Plan Soil Types on the Chehalis Reservation The Chehalis Reservation holds six soil classifications: CLASS I: Very little Class I land occurs in Western Washington. There is one small section subject to flooding and not currently used for agriculture. Symbol Name Class Woodland Ce Chehalis Loam 0-2% I 2o CLASS II: Class II is the largest soil class, subject to annual flooding good for agriculture. Symbol Name Class Woodland Suitability 8a Abiqua Silty Clay Loam IIw F4-Ig, F4G Arta silt loam IIw 30Hp Ca Camas clay loam IIs 3c 12A Chehalis silt loam IIw OwHp Cf Chehalis silty clay loam IIs 2o 13A Cloquqato silt loam IIw OwHp CLASS III: Class III are generally found next to Class II soils and are generally found near the river or lower and are subject to more frequent and deeper flooding. In some cases, there is winter ponding and they are found narrow, lower, flood channels that interface with Class II soils. Symbol Name Class Woodland Suitability 22A Bear Prairie Silt Loam IIIs 20Hp Cb Camas gravelly loam IIIs 3c Nb Newberg sandy loam, 20% IIIs 3c 59A Newberg silt loam IIIw 2o 87A Rennie silty loam clay loam IIIw OwHp Wc Wapato silty clay loam IIIw OwLp Chapter 4 Page 41 Chehalis Reservation Natural Hazards Mitigation Plan CLASS IV: Class IV is caused by frequent and severe flooding, is generally clayey, or silty, and is poorly drained. There are few narrow bands found. Symbol Name Class Woodland 77L Klone gravelly silt loam IVe 2fHp 18A Nemah gravelly silt loam IVw OwLp Ra Reed clay IVw CLASS V: Class V is the second largest types of soils found. Class V soils are composed of gravelly terrace soils and excessively drained. They are typical prairie soils become very dry in the summer season. Symbol Name Class Woodland Fa Fitch gravelly 0-3% VIs 4f sandy loam Fb Fitch gravelly sandy loam 3-15% VIs 4f 30A Sol Duc gravelly loam Vis 3fHp 8A Spanaway very gravelly sandy loam Vis 3fMp Sh Spanaway gravelly sandy loam Vis 3f Class VII & VIII: These soils are essentially gravelly bars or sandy bars along the river. Symbol Name Class Woodland Rw Riverwash VIIIw Ow Ma Alluvial Land VIIIw OwHp Impacts Approximately 75 percent of the Chehalis Reservation is located on an active floodplain that is subject to significant flooding up to five times annually. Flooding within the Chehalis Reservation restricts access to the Reservation for periods of one or more days, isolating portions of the Reservation, and may cause failure of individual water and waste water systems. Severe flooding also can contribute to the formation of swift-moving water in floodways that is capable of significantly endangering residents and their property. Flooding of this type can affect more than two-thirds of the Chehalis Reservation. The high frequency of flooding is caused by the unique geologic and physical environment of the Chehalis Reservation. These minor floods occur on the west, central, and eastern areas of the Chehalis Reservation, and cover up to half of the Reservation for periods of one or more days. December 2007 Flood. Source: Chehalis Tribe Chapter 4 Page 42 Chehalis Reservation Natural Hazards Mitigation Plan Flooding of local roads limits access to and from higher ground atop the two glacial terraces. These two areas become isolated “islands” during most flooding events. Flood-related impacts to the Chehalis Reservation typically increase with an increase in the significance of the flood event. Moderate events jeopardize roads, bridges, property fences, outbuildings, wells and septic systems, and other structures (including private residences) constructed before the adoption of the Chehalis Flood Damage Prevention Ordinance. During such floods, residents of the central part of the Chehalis Reservation must be evacuated to higher ground. During past events, flooding has resulted significant damages to private and commercial properties and the evacuation of people from homes built on low ground. During such events, it may be difficult or impossible to leave the reservation for up to seven days. A tragic example of the isolation created by flooding occurred during the 1996 flood, when the Tribe experienced a fatality resulting from the inability to access emergency medical care. Major floods resulting in severe impacts, including evacuation of people from residences in low-lying areas, and the inundation of major access roads, such as U.S. Highway 12, has historically occurred every 9 to 11 years. Consecutive years of major flooding (double floods) occur about every 20 years. The 1996 flood covered 75 percent of the reservation with measured flood depths up to 10 feet. All access routes, including Howanut Road, Anderson Road, and Moon Road were under one to four feet of fast-moving water. U.S. Highway 12, which provides access to many secondary roads, also was flooded, and Interstate 5 was flooded and closed for several days. To improve emergency access, in 2002 the Tribe rebuilt Anderson Road. They elevated and straightened portions of the road and fitted it with nineteen (19) culverts to allow passage of most flood waters beneath the road. A hydraulic model was prepared prior to engineering and design of the road, assuring that the road construction resulted in no net loss of floodplain storage During the 2007 flood, homes in the central area of the reservation were inundated with up to four feet of water. The water moved swiftly and covered the reservation to record water depths within 24 hours of notification of flooding. At the east end of the Chehalis Reservation, water overtopped Anderson Road. Up to two feet of water overtopped U.S. Highway 12 and flowed into the Black River east of Anderson Road. Southeast of the Reservation, Independence Road was overtopped near the bridge and a section of the Chehalis River channel migrated south and eroded a portion of the abandoned railroad grade. The central portion of the Chehalis Reservation, at the confluence of the Chehalis and Black rivers, was flooded from U.S. Highway 12 south to the abandoned railroad grade. Floodwater ponded upstream of the western glacial terrace and rose high enough to overtop Blockhouse Road and flow down Harris Creek. Between the glacial terrace and Oakville, bridges and culverts were overtopped, road pavement was damaged, and houses were flooded. At the west end of the Reservation, portions of Balch Road were damaged and the east approach to the Sickman-Ford Bridge was overtopped and damaged. Elsewhere within the Chehalis Reservation, gravel driveways and rural roads were scoured clean of gravel. Chapter 4 Page 43 Chehalis Reservation Natural Hazards Mitigation Plan Reservation flooding has frequently damaged homes, including flooring, walls, electrical, plumbing, wells, septic, heating. Flooding destroys vehicles and mechanical equipment. Residents lose household items including furnishings, clothing, appliances, food, personal keepsakes and household pets. They become homeless for weeks or months until their homes are repaired or they can find other lodging. The Chehalis Reservation has a housing shortage and replacement housing can be difficult to locate. Cleanup and recovery is stressful and further traumatizes flood victims. Children miss schools days; parents may lose income during the disruption. Reservation enterprises are closed during moderate to major flooding and lose revenue as customers and workers are unable to access businesses due to road closures and damaged roads. Residents living on high ground on the reservation are unable to leave during major flooding to go to work. Children cannot leave the reservation to attend school. Access to specialty medical care is completely blocked. Firefighters cannot access the reservation for medical assistance calls or to fight fires. Homes that are not flooded are still likely to lack clean domestic water or sewer services due to overtopping of well heads and damage to pumps. Data Data limitations were not found, historic data, National Weather Service, USGS information on floods in the area nearby the Chehalis Reservation. Telephone conversations with Ted Buehner, Warning Coordination Meteorologist, National Weather Service, and Seattle/Tacoma added open invitations to educate the public on StormWatchers and methods to incorporate the Tribe into “StormReady” program. CHEHALIS AWARENESS Twenty-two (22) of 22 people interviewed, ranked flooding as the number one hazard on the Reservation. Chapter 4 Page 44 Chehalis Reservation Natural Hazards Mitigation Plan Yakwałt&mx (K ink ade) Thunderbird and Whale Thunderbird is a bird of monstrous size and lives in a dark hole under the foot of t h e O l y m p i c g l a c i a l f i e l d . T h u n d e r b i r d s o a r e d f r o m h e r d ar k h o l e i n t h e m o u n t a i n s , far out over the placid waters and there poised herself high up in the air and waited for Whale to come to the surface of the water. Whale came and as quick as a flash, the powerful bird darted and seized it Whale in her flinty talons. Then, above the watery surface she lifted Whale and with great effort soared away toward the land areas. Passing beyond the oceans with her ponderous load, she was compelled to alight and rest her wings. Each and every time Whale was allowed to reach solid land there was a terrible battle; for Whale was powerful and fought for its life with terrible energy. Again Thunderbird would seize Whale; again Whale would escape. Again Thunderbird caught Whale. High into the air Thunderbird carried Whale over the land, dropping it to the land surface. Then, at this place there was another great battle. Thunderbird finally carried Whale to its nest in the lofty mountains, and there was the final and terrible contest fought. There was shaking, jumping up and trembling of the earth beneath, and a rolling up of the great waters... (Sciences) Earthquake Probability Based upon data collected from the Pacific Northwest Seismic Network, in the last 129 years the average earthquakes had a magnitude of 5.716, a range of 7.1 – 4.9 magnitude with 27 occurrences making it a 20.9% probability in the next 129 years. The King County Hazard Mitigation Plan simply states Moderate Probability/High Impact (p 5-21). Grays Harbor County Hazard Mitigation Plan scored earthquake an 11 out of possible 12. (p75) Thurston County gave earthquake a “high probability of occurrence with high vulnerability” (p IV-6). However, according to Mazzotti and Adams, the last great earthquake along the Cascadian Subduction Zone was ~1700 A.D. and future occurrence “shows an interesting bimodal pattern of recurrence interval with long (more than 700 years) and short (less than 450 years) intervals” (p1956). That would estimate their probability dates of occurrence, for a great (M~9) earthquake along the Cascadian Subduction Zone, at 2150 A.D. to 2150 A.D. (+/-130 years). Nevertheless, our communities should prepare for a seismic event no matter WHAT the simple and complicated statistics predict. Because according to Huff, “common errors, both intentional and unintentional, associated with the interpretation of statistics, and these errors can lead to biased or inaccurate conclusions.” Identification and Profile According to Rogers, “the principal hazards from earthquakes are surface faulting, ground failure and ground shaking”. (Rogers) Rogers states, “Surface faulting accompanies many large earthquakes, particularly in the western United States, and occurs when rock on either side of a fault is displaced at the earth’s surface. The slip may be vertical, horizontal, or a combination of both. In major earthquakes, the movement along a fault can be as much as (35) feet and the length of the surface rupture as great as 250 miles. Even small amounts of slip can Chapter 4 Page 45 Chehalis Reservation Natural Hazards Mitigation Plan disrupt power, water supply, and communication lines. In an area where the fault line and roads cross, vertical slip greater than a few inches can completely disrupt transportation infrastructure. In addition, faults that pass under structures are likely to cause severe structural damage if slippage occurs. (Rogers 113) Ground failure (which includes landslides, liquefaction and settlement) is induced by earthquake shaking in some geologic materials having unfavorable physical properties. (Rogers 113) Liquefaction occurs when ground shaking produces high water pressure under the earth’s surface and causes sand layer to act as liquid. (Rogers 115) Settlement is simply compaction of loose soils. This phenomenon can be damaging to roadways, particularly near bridge abutments, where the roadbed may settle while the bridge remains fixed. (Rogers 115) Although all of these earthquake-induced phenomenon’s can play an important part in causing damage, it is possible to experience an earthquake in which the damage is caused solely by ground shaking. In fact, in most earthquakes, ground shaking is the greatest hazard, causing the largest percentage of damage. Ground shaking is caused by earth waves that travel away from the earthquake source and may cause damage at distances of as much as 50-75 miles. (Rogers 116) Site conditions are a major element affecting the likely intensity of ground shaking. Thick soils overlying solid rock intend to increase the level of ground shaking and prolong the duration of shaking. The degree to which this effect takes place is dependent on certain physical properties of the soil, especially its velocity, density, and thickness relative to the underlying rock. (Rogers 117) Larger and longer ground motions could cause total collapse”. (Rogers 118) Chapter 4 Page 46 Chehalis Reservation Natural Hazards Mitigation Plan Geology Map of the Chehalis Valley LEGEND Qal ‐ Alluvium, deposits of silt, sand and clay left by flood waters QV ‐ Vashon drift – the older, higher terraces of outwash sand and gravel from the Vashon glacier Geology Geology of the Chehalis River Valley is a thick deposit of glacial sand and gravel filling the entire area between the Black Hills to the North and the Doty Hills to the South. Recent geomorphology created rich bottomland in between higher gravelly terraces. Ground water percolates easily through the permeable gravelly outwash deposits and the underlying bedrock serves to conserve this water at depths of less than 100 feet. The porous gravelly outwash deposits allow easy lateral as well as vertical movement of the water. Depths of the largest Washington earthquakes are not precisely known because the calculations of depth require a number of seismograms for each earthquake. Before 1949, the number of earthquakes and their locations and sizes were determined Chapter 4 Page 47 Chehalis Reservation Natural Hazards Mitigation Plan almost entirely using newspaper accounts of reported damage. As a result, information about early earthquakes is incomplete, the locations, depths and sizes of these earthquakes is less precise than those earthquakes recorded after 1969 by the University of Washington multi-station seismograph network (Linda Noson). Exceptions include the 1949, magnitude 7.1, Olympia earthquake and the 1965, magnitude 6.5 earthquake as they were large enough to be recorded at many seismograph stations around the world. An interesting fact about this pair of earthquakes is the lack of aftershocks. According to Algermissen and Perkins, a lack of aftershock is considered a characteristic of a deep earthquake. Most of the early large earthquakes in the Puget Sound region were deep. (Perkins) The size of an earthquake is indicated by a number called magnitude. Magnitude is calculated from a measurement of either amplitude or duration of specific types of recorded seismic waves recorded on seismograms. The Richter scale assigns numerical estimates of the size of an earthquake. The unit assigned to the logarithmic relation to recorded ground motion increase in size by a factor of 10. The force at which an earthquake shakes the ground is measured with the Richter scale, which rates the earthquake's actual force on a scale from 0 to 9. A 0 level Richter rating cannot even be felt by a person, while a rating of 8 shakes hard enough to crumble buildings. The Richter scale is based on a reading from a seismograph — a device that detects the waves sent out by an earthquake. Each number on the Richter scale indicates an increase of ten times the force of the previous number. For example, the Richter scale rating of 2 is ten times the force of a level 1. A Richter scale level of 3 is ten times more powerful than a level two and one hundred times more powerful than a level l, etc. The intensity of an earthquake is indicated by the amount of ground shaking at a particular site, and determined from reports of human reaction to shaking, damage done to structures and other effects. The Modified Mercalli Intensity (MMI) scale is the most commonly used scale to rank earthquakes in the United States. Modified Mercalli Intensity (MMI) Scale (Wood) 1. 2. 3. 4. 5. 6. 7. Not felt by a very few under especially favorable circumstances. Felt only by a few persons at rest, especially on upper floors of buildings. Delicately suspended objects may swing. Felt quite noticeably by persons indoors, especially on upper floors of buildings. Many people do not recognize it as an earthquake. Standing motor cars may rock slightly. Vibration is similar to the passing of a truck. Duration estimated. Felt indoors by many, outdoors by few during the day. At night, some awakened. Dishes, windows, doors disturbed; walls make cracking sounds. Sensations like a heavy truck striking a building. Standing motor cars rocked noticeably. Felt by nearly everyone; many awakened. Some dishes and windows broken; unstable objects overturned. Pendulum clocks may stop. Felt by all; many frightened. Some heavy furniture moved; a few instances of fallen plaster. Damage slight. Damage negligible in buildings of good design and construction; slight to moderate in wellbuilt ordinary structures; considerable damage in poorly built or badly designed structures; some chimneys broken. Noticed by persons driving in motor cars. Chapter 4 Page 48 Chehalis Reservation Natural Hazards Mitigation Plan 8. 9. 10. 11. 12. Damage slight in specially designed structures; considerable in ordinary substantial buildings with partial collapse. Damage great in poorly built structures. Fall of chimneys, factory stacks, columns, monuments, walls. Heavy furniture overturned. Damage considerable in specially designed structures; well-designed frame structures thrown out of plumb. Damage great in substantial buildings, with partial collapse. Buildings shifted off foundations. Some well-built wooden structures destroyed; most masonry and frame structures thrown out of plumb. Rails bent. Few, if any masonry structures remain standing. Bridges destroyed. Rails bent greatly. Damage total. Lines of sight and level distorted. Objects thrown into the air. Therefore, earthquake hazard can be defined as the probability of occurrence of a specified level of ground shaking in a specified period of time. Earthquake risk is defined as the expected or probable life loss, injury, or building damage, given the probabilities that specific levels of ground shaking occur. (Rogers 120) Earthquake – Historic Profile Historically, strong earthquakes have occurred in the Puget Sound region between Olympia and the Canadian border, in the Cascade Mountains and along the Washington-Oregon border. (Linda Noson) On December 14, 1872, a MMI VI earthquake in the Cascade Mountains was felt over 390,000 square kilometers, extending as far south as Eugene, Oregon and north into British Columbia and possibly into Alaska. (Hake) On January 11, 1909, a MMI VI earthquake in Blaine, Washington, near the northern border of Washington, was felt over 65,000 square kilometers. (Hake) On January 23, 1920, a MMI VII earthquake occurred near the Strait of Georgia, in the northern region of Washington, and was felt as far away as Anacortes and Bellingham, north to Vancouver Island, British Columbia. (Hake) On July 15, 1936, a magnitude 5.75 or MMI VII earthquake was centered in the southeastern region, near Walla Walla, Washington and Milton, Oregon. The total damage amounted to about $100,000 and was felt over 272,000 square kilometers, including most of Washington, Oregon and northern Idaho. (Hake) On April 29, 1945, a MMI VI – VII earthquake was reported causing minor damage, about 100 miles from Chehalis, in North Bend, Palmer and Stampede Pass. The earthquake was felt over the 130,000 square kilometers or over the greater portion of Washington, a small section of western Idaho and in the vicinity near Portland, Oregon. (Hake) On February 14, 1946, a MMI VII earthquake caused a few deaths and damage estimated at $250,000. The damage included cracked plaster and slight chimney failure with a few cases of building damage in Seattle, less than 100 miles from Chehalis. The earthquake was felt over 182,000 square kilometers from southwestern British Columbia to northwestern Oregon. (Hake) Chapter 4 Page 49 Chehalis Reservation Natural Hazards Mitigation Plan On June 23, 1946, a 7.3 magnitude earthquake was reported in the Strait of Georgia, less than 100 miles from Chehalis, causing one death, heavy damage and tsunamis. Damage reports included flooding of fields and highways, fallen chimneys, and damage to industrial and residential buildings. The earthquake was felt at Bellingham, Olympia, Raymond, Tacoma, areas in Canada and an estimated 260,000 square kilometers. (Hake) On April 13, 1949, a MMI VIII earthquake caused an estimated $25 million dollars in property damage near Olympia, less than 100 miles from Chehalis. Eight deaths were caused, nearly all buildings in Olympia were damaged, water and gas mains were broken, and property damage included toppled chimneys and cracked walls. Power and communication networks were interrupted, transportation was suspended for several days, and railway bridges were ordered out of commission. The earthquake was felt in western Canada, eastward to western Montana and southward to Cape Blanco, Oregon. The total area affected was 400,000 square kilometers. (Hake) On November 5, 1962, a MMI VII earthquake caused minor damage in Vancouver, Washington, and was located about 100 miles from Chehalis; the earthquake also affected Portland, Oregon. Numerous chimneys were damaged, several buildings reported fallen ceiling tiles, cracked plaster and broken windows. The total area affected was over 52,000 square kilometers of Washington and Oregon. (Hake) On April 29, 1965, a MMI VII – VIII earthquake caused about $12.5 million in damage throughout 340,000 square kilometers in northeastern region of Washington, parts of Oregon, northern Idaho, northwestern Montana and part of British Columbia. Three persons were killed by falling debris and four elderly women perished from heart failure attributed to the earthquake. (Hake) On December 20, 1973, the largest earthquake in eastern Washington was a shallow 4.4 magnitude incident. The earthquake was located near Othello, located about 300 miles from Chehalis. (Linda Noson) On May 16, 1976, a 5.1 magnitude earthquake was located in the Puget Sound area, located about 100 miles from Chehalis. (Linda Noson) On September 8, 1976, a 4.5 magnitude earthquake was centered in the southern Puget Sound basin, about 100 miles from Chehalis. (Linda Noson) On March 11, 1978, a 4.6 magnitude earthquake was centered near Bremerton, Washington, located less than 100 miles from Chehalis. The main shock was followed by 44 aftershocks. (Linda Noson) Beginning on March 24, 1980 through May 21, 1980, Mount St. Helens, located about 100 miles from Chehalis, generated 312 earthquakes with an average magnitude of 4.5. (Network) Chapter 4 Page 50 Chehalis Reservation Natural Hazards Mitigation Plan On February 13, 1981, a magnitude 7.3 earthquake was felt over 102,000 square kilometers and had more than 1,000 aftershocks distributed over the St. Helen’s Zone. Weaver and Smith estimate that the St. Helen’s Seismic Zone could be capable of generating a magnitude 7.0 + earthquake. (Linda Noson) On February 28, 2001, a magnitude 6.8 earthquake struck western Washington at 10:55 am local time. The epicenter was located approximately 11 miles northwest of the capitol, Olympia, located less than 30 miles from Chehalis, and 36 miles southwest of Seattle. Two aftershocks of magnitudes higher than 2.5 were recorded during the first 48 hours after the main shock. (Filiatrault A.) On March 1, 2001, a Presidential declaration (FEMA-1361-DR, Washington) was issued for 22 declared counties and 24 Tribal Nations. (FEMA) On July 31, 2001, FEMA released a summary of the Disaster Assistance totals from this incident. Washington residents and businesses received $129.7 million in recovery aid and 41,032 registrations from this disaster exceed the combined total of all other previous Washington disasters. Since the March 1, 2001 Presidential declaration, $50.02 million in aid has been approved for temporary disaster housing assistance and minimal repair grants. Inspectors have completed 36,808 damage verifications in the declared counties. The Small Business Administration has approved $76.82 million in low interest loans to homeowners, renters and businesses of all types. The Individual and Family Grant program has approved $2.86 million for residents affected by the earthquake. The Chehalis Tribe government was reimbursed for $30,000 damage to tribal governmental facilities. Table 3.5 FEMA Disaster Assistance Totals July 31, 2001 County Registrations Grays Harbor Lewis Thurston Chehalis Tribe Totals Chapter 4 2,075 Approved Temporary Housing Assistance $3,556,692 SBA Approved Disaster Loans $2,166,400 1,215 5,386 0 $1,797,346 $5,632,584 0 $2,073,400 $12,916,900 0 8,676 $10,986,622 $17,156,700 Page 51 Chehalis Reservation Natural Hazards Mitigation Plan FUTURE EARTHQUAKE POTENTIAL Cascadia Subduction Zone The Cascadia Subduction Zone (CSZ) is a very long sloping fault that stretches from Vancouver Island to Northern California. It separates the Juan de Fuca and North American plates. CSZ is where the two plates meet. Great Subduction Zone earthquakes are the largest earthquakes in the world and can exceed 9.0. Earthquake size is proportional to fault area – the last known great earthquake in the northwest was in January 1700, just over 300 years ago. Geological evidence indicates that great earthquakes may have occurred at least (7) seven times in the last 3,500 years suggesting a return time of about 400 to 600 years. Impacts The impact from earthquakes to communities is well-evidenced by the catastrophic events around the world; San Franciso in the United States; Kobe, Japan; Chengdu, China and Kashmire, Pakistan. Failed bridges, building and other structures can tran or bury people causing injury or death. Damage to community infrastructre is common and distrupts public and private commerce and services. Disruptions are Chapter 4 Page 52 Chehalis Reservation Natural Hazards Mitigation Plan widespread and include communication, electrical, heat fuel, auto fuel and domestic water. Structural fires are a secondary hazard from earthquakes. Individuals may be displaced due to damaged homes or lack heat, light, water and/or sewer facilities. Major earthquakes may prevent travel to obtain services or aid. Subsequent econmic impacts to businesses are likely following an earthquake. Structures built since 2002 on the Chehalis Reservation are built to modern code, but structures built prior are likely to be vulnerable to ground shaking. Fire fighters and law enforcment can quickly become over-extended with response and recover operations. All fire assistance comes from outside the reservation and may face barriers due to disruption of transportation facilities or maybe unable to respond to the reservation community due to priority calls within their primary response area. Tribal services can expect a high number of requests for assistance to law enforcement, health and social services. Building and structural inspections will become priorities for planning and permitting services personnel and disrupt other operations. Tribal government may also be expected to house and feed tribal members is their residences are unihabitable due to damage or until residences are inspected. Disruption to phone and transportation services may leave some residences stranded or trapped and unable to call or send for assistance making search and rescue operations necessary. Data There were no issues of data limitations and data was obtained though the use of internet, library, journal, and scientific sources available to the public. An analysis of Tribal vulnerabilities focuses upon the public meeting input. The Tribal community members were more concerned with floods in the area and not actively concerned with earthquake. Chapter 4 Page 53 Chehalis Reservation Natural Hazards Mitigation Plan CHEHALIS AWARENESS From the Household Natural Hazards Preparedness Questionnaire, 83% of the reservation has experienced a natural disaster; however, only 53% of the reservation had experienced an earthquake. When asked the level of concern regarding earthquakes, with choices from (1) extremely concerned; (2) very concerned; (3) concerned; (4) somewhat concerned to (5) not concerned, a majority (40%) of the surveyed population chose (3) concerned. Only 7% of the surveyed population said that they were, “extremely concerned” about earthquake danger. Chapter 4 Page 54 Chehalis Reservation Natural Hazards Mitigation Plan SEVERE WINTER STORM PROBABILITY According to Washington State Mitigation Plan, Counties Most Vulnerable to High Winds, with a recurrence rate of >100% - at least one occurrence per year, Thurston County is vulnerable to meteorological conditions, with a 175% recurrence rate; Grays Harbor County is vulnerable to meteorological conditions with a 170% recurrence rate. (Pudlo) According to Washington State Mitigation Plan, Counties Most Vulnerable to Winter Storms, with a recurrence rate of >100% - at least one occurrence per year, Thurston County is vulnerable to meteorological conditions, with a 50% recurrence rate; Grays Harbor County is not vulnerable to meteorological conditions with a 40% recurrence rate. (Pudlo) Hazardous Weather Seasons 1. Flood season: Western Washington – November through February 2. Windstorm season: October through March. 3. Snow season: Western Washington – mid November through mid March. High winds – The National Weather Service defines high winds as sustained winds of 40 mph or gusts of 58 mph or greater, not caused by thunderstorms, expected to last for an hour or more. Areas most vulnerable to high winds are those affected by a strong pressure difference from deep storms originating over the Pacific Ocean; an outbreak of very cold, Arctic air originating over Canada; or air pressure differences. Areas considered most vulnerable to high winds are 1) those most affected by conditions that lead to high winds, as described above, and 2) those with a high wind recurrence rate of 100 percent, meaning the area experiences at least one damaging high wind event every year. (Pudlo) Winter storm – The National Weather Service defines a winter storm as having significant snowfall, ice, and/or freezing rain; the quantity of precipitation varies by elevation. Heavy snowfall is 4 inches or more in a 12-hour period, or 6 inches or more in a 24-hour period in non-mountainous areas; and 12 inches or more in a 12-hour period or 18 inches or more in a 24-hour period in mountainous areas. Areas most vulnerable to winter storms are those affected by convergence of dry, cold air from the interior of the North American continent, and warm, moist air off the Pacific Ocean. Typically, significant winter storms occur during the transition between cold and warm periods. Areas considered most vulnerable to winter storm are 1) those most affected by conditions that lead to such storms, as described above, and 2) those with a recurrence rate of 50 percent, meaning the area experiences at least one damaging winter storm event every two years. (Pudlo) FEMA reports four severe storm disaster declarations in 2006 and 2007 for Grays Harbor County that caused damage or threats to the reservation population (Disaster Numbers 1734, 1682, 1671, 1641). Chapter 4 Page 55 Chehalis Reservation Natural Hazards Mitigation Plan IDENTIFICATION AND PROFILE A severe storm is an atmospheric disturbance that results in one or more of the following phenomena: strong winds and large hail, thunderstorms, tornados, rain, snow, or other mixed precipitation. Typically, major impacts from a severe storm are to transportation infrastructure, services and loss of utilities. Most storms move into Washington from the Pacific Ocean. Considered for this profile are the following severe storm elements (using National Weather Service definitions): 1. High winds – Storms with sustained winds of 40 mph or gusts of 58 mph or greater, not caused by thunderstorms, expected to last for an hour or more. 2. Winter storm – A storm with significant snowfall, ice, and/or freezing rain; the quantity of precipitation varies by elevation. Heavy snowfall is 4 inches or more in a 12-hour period, or six or more inches in a 24-hour period in non-mountainous areas; and 12 inches or more in a 12-hour period or 18 inches or more in a 24-hour period in mountainous areas. Precipitation is recorded 20 to 25 days or more each month and December and January are the wettest months. Snowfall is light in the lower elevations. During the wet season, rainfall is usually of light to moderate intensity and continuous over a period. The strongest winds are generally from the south or southwest and occur during the fall and winter. In interior valleys, wind velocities reach 40 to 50 mph each winter, and 75 to 90 mph a few times every 50 years. The highest summer and lowest winter temperatures generally occur during periods of offshore easterly winds. During most of the year, the prevailing wind is from the southwest or west. The frequency of northeasterly winds is greatest in the fall and winter. Wind velocities ranging from four to 12 mph can be expected 60 to 70 percent of the time; 13 to 24 mph, 15 to 24 percent of the time; and 25 mph or higher, 1 to 2 percent of the time. The highest wind velocities are from the southwest or west and are frequently associated with rapidly moving weather systems. Extreme wind velocities can be expected to reach 50 mph at least once in two years; 60 to 70 mph once in 50 years; and 80 mph once in 100 years. (Pudlo) According to the National Weather Service, there are three ingredients for a storm to develop cold air, moisture and lift. Cold air below freezing temperatures is necessary to make snow or ice. Air blowing over a body of water is an excellent source of moisture to form clouds and precipitation. To raise the moist air to form clouds and cause precipitation requires lift. An example of lift is warm air colliding with cold air and raising over the cold dome. The boundary between the warm and cold air masses is a front. Severe storms are dangerous and cause deaths in by traffic accidents on icy roads, death by hypothermia from prolonged exposure to cold and heart attacks from shoveling snow. (Pudlo 5-7 p3) According to the Center for Disease Control, carbon monoxide poisoning was a major health consequence of the severe storm in January of 1993. Because of the use of alternative sources of energy for indoor cooking and home heating, the risk of exposure to CO increased. (Control) Chapter 4 Page 56 Chehalis Reservation Natural Hazards Mitigation Plan Severe Storm – Historic Profile January/February 1916 – Seattle's Greatest Snowstorm was one of the top 10 weather events in Washington during the 20th Century, according to the National Weather Service, Seattle Forecast Office. Seattle’s snowfall in January was 23 inches, and February snowfall was 35 inches, for a two-month total of 58 inches. Seattle recorded its maximum snowfall ever in a 24-hour period, with 21.5 inches on February 1. Other parts of western Washington received between two to four feet of snow. Winds created snowdrifts as high as five feet. The region was crippled, with transportation essentially halted. January 13, 1950 – The January 1950 Blizzard was one of the top 10 weather events in Washington during the 20th Century, according to The National Weather Service, Seattle Forecast Office. On this date, 21.4 inches of snow fell in Seattle, the second greatest 24-hour snowfall recorded with 25-40 mph winds. January had 18 days with high temperatures of 32 degrees or lower. The winter of 1949-50 was the coldest winter on record in Seattle, with an average temperature of 34.4 degrees. October 12, 1962 – The Columbus Day Wind Storm was the top weather event in Washington during the 20th Century, according to the National Weather Service, Seattle Forecast Office. This storm is the greatest windstorm to hit the Northwest since weather recordkeeping began in the 19th century, and called the mother of all wind storms” in the 1900s. All windstorms in the Northwest are compared to this one. The Columbus Day Storm was the strongest widespread non-tropical windstorm to strike the continental U.S. during the 20th century, affecting an area from northern California to British Columbia. The storm claimed seven lives in Washington State; 46 died throughout the impacted region. One million homes lost power. More than 50,000 homes were damaged. Total property damage in the region was estimated at $235 million (1962 dollars). The storm blew down 15 billion board feet of timber worth $750 million (1962 dollars); this is more than three times the timber blown down by the May 1980 eruption of Mount St. Helens, and enough wood to replace every home in the state. Highest recorded wind speeds (before power went out at recording stations): 1. 2. 3. 4. Naselle, Washington Coast – gust to 160 mph. Bellingham and Vancouver – gusts of 113 mph. Renton – gust of 100 mph. Tacoma – gust of 88 mph. April 5, 1972 – Washington's Deadliest Tornado Outbreak was one of the top 10 weather events in Washington during the 20th Century, according to the National Weather Service, Seattle Forecast Office. Three tornadoes touched down in Washington State on this day: 1. An F3 tornado touched down in Vancouver; it swept through a grocery store, bowling alley, and grade school near where Vancouver Mall is today. It caused six deaths, 300 injuries, and $50 million in damage. Chapter 4 Page 57 Chehalis Reservation Natural Hazards Mitigation Plan 2. Later that day, another F3 tornado touched down west of Spokane near Davenport, and an F2 tornado struck rural Stevens County. 3. Numerous severe thunderstorms with large hail and damaging winds were reported over other areas of eastern Washington. An F3 tornado has winds of 158-206 mph, and is capable of severe damage. An F2 tornado has winds of 113-157 mph and is capable of considerable damage. Because of these tornados, Washington led the nation in tornado deaths in 1972. November 1990 – Statewide Flooding Federal Disaster #883 - Stafford Act disaster assistance provided $57 million. It was classified as one of the top 10 weather events in Washington during the 20th Century, according to the National Weather Service, Seattle Forecast Office. This storm caused widespread, major flooding on western Washington Rivers. This storm caused two deaths. Damage estimated at $250 million. December 1990 – Severe Storm Federal Disaster #896 - Stafford Act disaster assistance provided – $5.1 million. Causing floods, snow, and high winds. January 20, 1993 – The Inauguration Day Wind Storm Federal Disaster #981, Stafford Act disaster assistance provided – $24.2 million. This storm claimed five lives. December 1996 - January 1997 – Ice, Wind, Flooding, Snow-loading, Landslides Federal Disaster #1159 - Stafford Act disaster assistance provided – $83 million. Small Business Administration loans approved – $31.7 million. Saturated ground combined with snow, freezing rain, rain, rapid warming and high winds within a five-day period produced flooding and landslides. Twenty-four deaths; $140 million (est.) in insured losses; 250,000 people lost power. Impacts The Chehalis Reservation, like most of western Washington is vulnerable to high winds because of the climatic conditions and prevalence of 100 ft to 150 ft tall conifer trees. High winds weaken standing trees and structures weighted with snow or ice. Two predominating species, Douglas fir, which are planted extensively on the reservation as a timber crop and western hemlock have shallow later root systems with top heavy crown. Trees are vulnerable to falling when soils are soaked from ongoing rainfall. Sustained high winds and gusts cause tress to sway significantly; repetitive swaying can weaken a tree’s root hold in the saturated soils and force it to topple. Power lines, vehicles, homes and structures may be damaged. Transportation routes may be blocked. Falling tree limbs and debris can injure or cause death to individuals. Downed power lines may cause electrocutions. Severe winter storms cause wide spread power outages annually in our rural setting, which may take 2 to 5 days or longer to restore. Downed trees and debris hinder or prevent emergency response capabilities, forcing the closure of tribal government services and businesses. Homes without power may suffer from cold Chapter 4 Page 58 Chehalis Reservation Natural Hazards Mitigation Plan and hypothermia when winds are combined with snow and low temperatures. Improperly stored foods can become rancid and unsafe to eat. Some people may resort to trying to heat their home with outdoor grills, exposing themselves and their families to carbon monoxide poisoning. Risks of home fires increase as people try to use candles for light, or start wood fires in unsafe stoves or homes with faulty chimneys or flues. Medically vulnerable individuals may be at risk of severe health consequences for oxygen respirators or other equipment. The rural setting of the Chehalis Reservation can increase these impacts as the reservation is located at the furthest end of two county public utilities and often must wait longer for power restoration in the event of a storm. About 50% of the reservation population is dependent on well water, which must be pumped and septic systems with also utilize pumps. During power outages, many or most of our rural residents may be completely lacking drinking water or sewer services. When combined with flooding, this likelihood increases. Data The comprehensive data from the State of Washington Hazard Mitigation Plan is cited throughout this section. The references included: National Weather service, Seattle Times, FEMA and National Oceanic and Atmospheric Administration. CHEHALIS AWARENESS According to the Hazards Survey, over 40% of participants were “very concerned” about Severe Storms. Chapter 4 Page 59 Chehalis Reservation Natural Hazards Mitigation Plan VOLCANO IDENTIFICATION AND PROFILE A volcano is a mountain connected to a reservoir of molten rock below the surface of the earth. Volcanoes are built up by an accumulation of their own eruptive products, lava and ash. Though there are no volcanoes within Thurston County, active volcanoes in the Cascade Range, including Mt. Rainier to the east and Mt. St. Helens to the south, could affect Thurston County with mud and debris flow (lahar), flooding due to an upstream lahar, and ashfall. Mt. Saint Helens in Washington state, USA Volcano – Historic Profile Cascade Range volcanoes in the U.S. have erupted more than 200 times during the past 12,000 years for an average of nearly two eruptions per century. At least five eruptions have occurred during the past 150 years. The last major eruption of Mt. Rainier was more than 1,000 years ago. The most recent eruptions in the Cascade Range are the well-documented 19801986 eruptions of Mount St. Helens which claimed 57 lives and caused nearly a billion dollars in damage and response costs. The effects were felt throughout the northwest. Thurston County was affected by extensive ash fall which damaged internal combustion engines, caused transportation problems due to reduced visibility, and was a general nuisance. There was also an economic impact resulting from the closure of I-5. Over the past 200 years, Mount St. Helens has erupted three times, suggesting a recurrence interval of about 70 years. Mount St. Helens is located 49 miles south of the Chehalis Indian Reservation. Additional devastating impacts could result if winds move debris and ash toward Thurston County. This would disrupt transportation and other essential services, Chapter 4 Page 60 Chehalis Reservation Natural Hazards Mitigat [Text truncated at 120,000 characters. The full text is on the page linked above.] --- Source: Frix Law Library, https://www.frixlaw.com/law-library/documents/tribal%3Aconfederated_chehalis%3Aadf9872bdd7a0975. Public record. Not legal advice.