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Local tsunami evacuation analysis of Reedsport and Florence, Douglas and Lane Counties, Oregon,
by Laura L. S. Gabel, Fletcher O'Brien, and Jonathan C. Allan; 88 p. report, including tabloid-sized maps in appendices, one Esri® geodatabase with internal metadata, external metadata in .xml format.

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ABSTRACT
We evaluated in the event of a local tsunami generated by an earthquake on the Cascadia subduction zone (CSZ). We determined minimum walking times to safety (defined as ~20 ft beyond the inundation limit) for a moderate walking speed of 4 fps (feet per second, 22 minutes/mile) using least-cost distance (LCD) routes determined by modification of the anisotropic path distance method of Wood and Schmidtlein (2012) and Wood and others (2016). Four feet per second is the standard speed for pedestrians to cross at signalized intersections (U.S. Department of Transportation, 2012). Evacuation paths were limited to roads, trails, and pedestrian pathways designated by local government reviewers as the most likely routes.

To estimate whether pedestrians can stay ahead of a tsunami along the evacuation routes, we produced maps of:

The BTW maps depict the minimum evacuation speed required to stay ahead of the tsunami wave given a variety of scenarios that will increase evacuation difficulty. The primary scenario uses the existing road network and includes a 10-minute delay from start of earthquake before beginning evacuation. Additional challenges to evacuation are examined, including failure of non-retrofitted bridges and effects from liquefaction. In all cases, the identified minimum speeds must be maintained for the entire time it takes to evacuate from the inundation zone. Given the model limitations defined in the Methods section, results show that evacuation of the entire region is achievable at a moderate walking speed (4 fps) assuming the existing road and bridge network remains viable. Even for those with mobility limitations (i.e., those who cannot travel at speeds more than 4 fps), safety can be reached ahead of the wave from nearly every location within the city limits of Florence and Reedsport; this assumes the existing road and bridge network is not compromised. Evacuation challenges do exist in some of the outlying areas. Failure of the Salmon Harbor Bridge in Winchester Bay introduces evacuation challenges for evacuees starting from areas west of the bridge, and long distances to high ground and difficult walking conditions result in evacuation challenges for the open coast recreation areas on the Umpqua and Siuslaw Rivers.

Possible mitigation options include increasing the number of evacuation routes by constructing more earthquake-hardened bridges (built or remodeled to withstand shaking from a major earthquake); adding new evacuation routes; and/or installing a tsunami refuge, otherwise known as a vertical evacuation structure, on the Siuslaw Spit.


GEOGRAPHIC INFORMATION SYSTEM (GIS) DATA

Geodatabase is EsriĀ® version 10.1 format.
Metadata is embedded in the geodatabase and is also provided as separate .xml formatted files.

Florence_Reedsport_Tsunami_Evacuation_Modeling.gdb:
XXL1 Cascadia subduction zone earthquake
   rasters
         MaxTsunamiFlowDepth_XXL1 Depth of inundation (amount of water above ground surface) in meters in the evacuation zone. .xml
         TsunamiWaveArrival_XXL1 Wave arrival time in minutes in the evacuation zone. Wave arrivals are shown as the time when wave depth reaches 6 inches or greater at any location, and arrivals are timed from the start of the earthquake. .xml
 
   feature dataset - Bridges In, Winchester Bay Only
         EvacuationFlowZones_BridgesIn The nearest safety destination for every point in the inundation zone (on the road and trail network) assuming the existing road, trail, and bridge network remains intact. .xml
         EvacuationRoutes_BridgesIn The most efficient routes to safety for every point in the inundation zone (on the road and trail network) assuming the existing road, trail, and bridge network remains intact. .xml
         EvacuationTime4fps_Roads_BridgesIn Seamless data for the amount of time it takes to reach safety at a constant walking speed of 4 feet per second (fps) along all road, trail, and beach networks (per local government review) for the Winchester Bay area, Douglas County, Oregon. .xml
         EvacuationTime4fps_Trails_BridgesIn Minimum evacuation speeds needed to stay ahead of the wave assuming the existing road, trail, and bridge network remains intact. This feature class contains BTW data on trails and beach networks. .xml
         WalkingSpeeds_Roads_BridgesIn Minimum evacuation speeds needed to stay ahead of the wave assuming the existing road, trail, and bridge network remains intact. This feature class contains BTW data on paved roads only. .xml
         WalkingSpeeds_Trails_BridgesIn Minimum evacuation speeds needed to stay ahead of the wave assuming the existing road, trail, and bridge network remains intact. This feature class contains BTW data on trails and beach networks only. .xml
 
   feature dataset - Bridges Out
         EvacuationFlowZones_BridgesOut The nearest safety destination for every point in the inundation zone (on the road and trail network) assuming all non-retrofitted bridges within the inundation zone fail due to earthquake shaking. .xml
         EvacuationRoutes_BridgesOut The most efficient routes to safety for every point in the inundation zone (on the road and trail network) assuming all non-retrofitted bridges within the inundation zone fail due to earthquake shaking. .xml
         EvacuationTime4fps_Roads_BridgesOut Time required to reach the nearest safety destination for every point in the inundation zone based on a standard walking speed of 4 ft/sec assuming all non-retrofitted bridges within the inundation zone fail due to earthquake shaking. This feature class contains BTW data on paved roads only. .xml
         EvacuationTime4fps_Trails_BridgesOut Time required to reach the nearest safety destination for every point in the inundation zone based on a standard walking speed of 4 ft/sec assuming all non-retrofitted bridges within the inundation zone fail due to earthquake shaking. This feature class contains Beat the wave (BTW) data on trails and the beach only. .xml
         WalkingSpeeds_Roads_BridgesOut Minimum evacuation speeds needed to stay ahead of the wave assuming all non-retrofitted bridges within the inundation zone fail due to earthquake shaking. This feature class contains BTW data on paved roads only. .xml
         WalkingSpeeds_Trails_BridgesOut Minimum evacuation speeds needed to stay ahead of the wave assuming all non-retrofitted bridges within the inundation zone fail due to earthquake shaking. This feature class contains BTW data on trails and beach networks only. .xml