Living in Lahar Zones: Assessing Hazard Exposure, Risk Perception, and Preparedness Behaviors in Communities within the Mount Baker and Glacier Peak Volcanic Hazard Zones

摘要

As the number of people living at risk from volcanic hazards in the U.S. Pacific Northwest grows, more detailed studies of community hazard exposure, risk perception, and preparedness levels become critical to developing effective mitigation, response, and recovery plans. This thesis uses risk mapping and a knowledge, risk perception, and preparedness survey to examine the risk that lahars from Mount Baker and Glacier Peak volcanoes pose to nearby communities in the Skagit Valley (WA). The risk map component of this research identifies spatial variations in lahar risk and estimates potential losses associated with a maximum envisioned lahar. The survey component seeks to (1) explore the existence of a disconnect between accurate risk perception and adequate preparedness; (2) isolate the factors that facilitate or present barriers to the adoption of preparedness behaviors; and (3) determine how professional participation in hazard risk management influences knowledge, risk perception, and preparedness in the Skagit Valley. Elements of the Protective Motivation Theory (PMT) and Values-Beliefs-Norms (VBN) theory are used to frame the survey results.The risk maps generated in this study show that towns with populations smaller than 1,000 people (e.g., Concrete, Lyman) will likely be disproportionately affected by lahars, supporting the findings of Diefenbach et al. (2015). Lahar zones intersect large portions of these smaller towns, including critical roads that link them to nearby towns and emergency services. Such a loss of infrastructure would greatly reduce response capacity. Burlington represents one of the most at-risk towns in the Skagit Valley since a relatively large population (8,466) lives in this city that is almost entirely in the lahar zone. In a total loss scenario, the maximum envisioned lahar would place nearly 40,000 lives at risk along with extensive tracts of residential and agricultural land. Overall monetary damages could amount to over $5 billion (total assessed value) and nearly $62 million in tax revenue. Additional geologic modeling of lahar paths would greatly improve the ability to produce more complex loss scenarios.Results from over 500 survey responses indicate that a disconnect exists between perception and preparedness among respondents. The 82 percent of respondents who accurately anticipate that future volcanic hazards will impact the Skagit Valley fail to prepare more than those unaware of the hazard. When asked what prevents them from preparing, respondents deny that perceived response-efficacy and perceived protective response pose substantial barriers. Perceived self-efficacy and ascription of responsibility beliefs appear to play a more dominant role in determining preparedness behaviors, albeit a less readily recognized role. Ascription of responsibility beliefs (VBN) seems to explain an element of preparedness motivation not fully incorporated within PMT. Finally, results show that professional participation in response-related activities minimally influences household preparedness, but successfully improves perceived self-efficacy, confidence in officials, and information seeking behavior. Thus, participation’s affect on household preparedness may be tied to specific types of participation (e.g., public, professional, specific training programs), whereas self-efficacy and confidence in officials, being independent of participation type, may improve due to increased interaction with emergency officials.