Abstract
Tsunami-evacuation planning in coastal communities is typically based on maximum evacuation zones for a single scenario or a composite of sources; however, this approach may over-evacuate a community and overly disrupt the local economy and strain emergency-service resources. To minimize the potential for future over-evacuations, multiple evacuation zones based on arrival time and inundation extent are being developed for California coastal communities. We use the coastal city of Alameda, California (USA), as a case study to explore population and evacuation implications associated with multiple tsunami-evacuation zones. We use geospatial analyses to estimate the number and type of people in each tsunami-evacuation zone and anisotropic pedestrian evacuation models to estimate pedestrian travel time out of each zone. Results demonstrate that there are tens of thousands of individuals in tsunami-evacuation zones on the two main islands of Alameda, but they will likely have sufficient time to evacuate before wave arrival. Quality of life could be impacted by the high number of government offices, schools, day-care centers, and medical offices in certain evacuation zones and by potentially high population density at one identified safe area after an evacuation. Multi-jurisdictional evacuation planning may be warranted, given that many at-risk individuals may need to evacuate to neighboring jurisdictions. The use of maximum evacuation zones for local tsunami sources may be warranted given the limited amount of available time to confidently recommend smaller zones which would result in fewer evacuees; however, this approach may also result in over-evacuation and the incorrect perception that successful evacuations are unlikely.
Highlights
Tsunami-evacuation planning is challenging in coastal communities due to varying wave arrival times and inundation associated with local and distant tsunami
Evacuation Zone 1 is recommended for tsunamis with expected water elevation (FASTER value) of 0–1 m and focuses on the evacuation of beaches, piers, and harbor docks
The objective of this paper was to examine the population and evacuation implications for multi-zone evacuation planning summarized in tsunami-evacuation playbooks for coastal communities along the California coast
Summary
Tsunami-evacuation planning is challenging in coastal communities due to varying wave arrival times and inundation associated with local and distant tsunami. Some jurisdictions use a maximum tsunami hazard zone from a specific scenario (e.g., Butler 2014; Walsh et al 2000) or from a composite of multiple sources (e.g., Wilson et al 2010; California Department of Conservation 2015), both to simplify the public-education message and to maximize the likelihood that they have considered everyone who could be directly impacted by a tsunami Other jurisdictions, such as the State of Oregon (USA), display two zones on evacuation maps to distinguish local tsunami evacuations where immediate action is necessary if ground shaking is felt (e.g., from a Cascadia subduction zone earthquake in the case of coastal Oregon) and distant tsunami evacuations that will be facilitated by public officials over longer time periods (Priest et al 2016)
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