5/12/2020 Whitman County 2020 Hazard Mitigation Plan – Volume 1: Countywide Planning Elements May 2020 - Final Bridgeview Consulting, LLC BEVERLY O’DEA 915 N. LAUREL LANE TACOMA WA 98406 253.301.1330 Whitman County HAZARD MITIGATION PLAN UPDATE VOLUME 1: COUNTYWIDE PLANNING ELEMENTS Final May 2020 Prepared for: Whitman County Department of Emergency Management 310 N. Main Street Colfax WA 99111 Prepared by: Bridgeview Consulting, LLC 915 North Laurel Lane Tacoma, Washington 98406 253.301.1330 Whitman County Hazard Mitigation Plan Update; Volume 1—Countywide Planning Elements TABLE OF CONTENTS Executive Summary ............................................................................................................ ES-1 Introduction ............................................................................................................. 1 1.1 Authority ............................................................................................................................................. 1 1.2 Purpose of Hazard Mitigation Planning .............................................................................................. 1 1.3 Plan Adoption...................................................................................................................................... 2 1.4 Scope and Plan Organization .............................................................................................................. 2 Plan Methodology ................................................................................................2-1 2.1 Grant Funding .................................................................................................................................. 2-1 2.2 Defining the Planning Area .............................................................................................................. 2-1 2.3 Formation of the Core Planning Team ............................................................................................. 2-1 2.4 Establishment of the Planning Partnership ....................................................................................... 2-1 2.5 Coordination with Other Agencies ................................................................................................... 2-3 2.6 Review of Existing Programs ........................................................................................................... 2-4 2.7 Plan Development Chronology/Milestones ..................................................................................... 2-4 2.8 Public Involvement .......................................................................................................................... 2-6 2.8.1 Public Involvement Results ............................................................................................... 2-15 Whitman County Profile ......................................................................................3-1 3.1 Jurisdictions and Features ................................................................................................................ 3-1 3.2 Historical Overview ......................................................................................................................... 3-1 3.3 Major Past Hazard Events ................................................................................................................ 3-2 3.4 Physical Setting ................................................................................................................................ 3-3 3.4.1 Geology ............................................................................................................................... 3-3 3.4.2 Scablands ............................................................................................................................ 3-3 3.4.3 Soils ..................................................................................................................................... 3-6 3.4.4 Climate ................................................................................................................................ 3-6 3.5 Critical Facilities and Infrastructure ................................................................................................. 3-7 3.6 Demographics .................................................................................................................................. 3-8 3.6.1 Population Characteristics ................................................................................................. 3-10 3.6.2 Income ............................................................................................................................... 3-10 3.6.3 Age Distribution ................................................................................................................ 3-11 3.6.4 Race, Ethnicity and Language ........................................................................................... 3-12 3.7 Economy ........................................................................................................................................ 3-13 3.7.1 Industry, Businesses and Institutions ................................................................................ 3-13 3.7.2 Employment Trends and Occupations .............................................................................. 3-14 3.8 Future Land Use ............................................................................................................................. 3-17 Risk Assessment Methodology ..........................................................................4-1 4.1 Overview .......................................................................................................................................... 4-1 4.2 Methodology .................................................................................................................................... 4-1 4.2.1 Hazard Identification ........................................................................................................... 4-2 4.2.2 Hazard Profiles .................................................................................................................... 4-3 4.2.3 Risk Assessment Process .................................................................................................... 4-3 4.2.4 Hazus and GIS Applications ............................................................................................... 4-4 Bridgeview Consulting i May 2020 Whitman County Hazard Mitigation Plan Update; Volume 1—Planning-Area-Wide Elements 4.2.5 Calculated Priority Risk Index Scoring Criteria ................................................................. 4-7 4.4 Community Variations to the Risk Assessment ............................................................................. 4-12 4.5 Limitations ..................................................................................................................................... 4-12 Dam Failure .........................................................................................................5-1 5.1 General Background ......................................................................................................................... 5-1 5.1.1 Causes of Dam Failure ........................................................................................................ 5-1 5.1.2 Regulatory Oversight .......................................................................................................... 5-1 5.2 Federal Energy Regulatory Commission ......................................................................................... 5-3 5.3 Hazard Profile .................................................................................................................................. 5-3 5.3.1 Previous Occurrences .......................................................................................................... 5-3 5.3.2 Extent and Location ............................................................................................................ 5-3 5.3.3 Frequency ............................................................................................................................ 5-5 5.3.4 Severity ............................................................................................................................... 5-5 5.3.5 Warning Time ..................................................................................................................... 5-5 5.4 Vulnerability Assessment ................................................................................................................. 5-6 5.4.1 Impact on Life, Health, and Safety ..................................................................................... 5-6 5.4.2 Impact on Property .............................................................................................................. 5-6 5.4.3 Impact on Critical Facilities ................................................................................................ 5-6 5.4.4 Impact on Environment ....................................................................................................... 5-6 5.4.5 Impact on Economy ............................................................................................................ 5-6 5.4.6 Impact from Climate Change .............................................................................................. 5-7 5.5 Secondary Hazards ..........................................................................................................................