Beat-the-wave evacuation mapping for tsunami hazards in Seaside, Oregon, USA

Natural Hazards
State of Oregon Department of Geology and Mineral Industries
By: , and 

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Abstract

Previous pedestrian evacuation modeling for tsunamis has not considered variable wave arrival times or critical junctures (e.g., bridges), nor does it effectively communicate multiple evacuee travel speeds. We summarize an approach that identifies evacuation corridors, recognizes variable wave arrival times, and produces a map of minimum pedestrian travel speeds to reach safety, termed a “beat-the-wave” (BTW) evacuation analysis. We demonstrate the improved approach by evaluating difficulty of pedestrian evacuation of Seaside, Oregon, for a local tsunami generated by a Cascadia subduction zone earthquake. We establish evacuation paths by calculating the least cost distance (LCD) to safety for every grid cell in a tsunami-hazard zone using geospatial, anisotropic path distance algorithms. Minimum BTW speed to safety on LCD paths is calculated for every grid cell by dividing surface distance from that cell to safety by the tsunami arrival time at safety. We evaluated three scenarios of evacuation difficulty: (1) all bridges are intact with a 5-minute evacuation delay from the start of earthquake, (2) only retrofitted bridges are considered intact with a 5-minute delay, and (3) only retrofitted bridges are considered intact with a 10-minute delay. BTW maps also take into account critical evacuation points along complex shorelines (e.g., peninsulas, bridges over shore-parallel estuaries) where evacuees could be caught by tsunami waves. The BTW map is able to communicate multiple pedestrian travel speeds, which are typically visualized by multiple maps with current LCD-based mapping practices. Results demonstrate that evacuation of Seaside is problematic seaward of the shore-parallel waterways for those with any limitations on mobility. Tsunami vertical-evacuation refuges or additional pedestrian bridges may be effective ways of reducing loss of life seaward of these waterways.

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Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Beat-the-wave evacuation mapping for tsunami hazards in Seaside, Oregon, USA
Series title Natural Hazards
DOI 10.1007/s11069-015-2011-4
Volume 80
Issue 2
Year Published 2016
Language English
Publisher Springer
Contributing office(s) Western Geographic Science Center
Description 25 p.
First page 1031
Last page 1056
Country United States
State Oregon
Online Only (Y/N) N
Additional Online Files (Y/N) N