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Open-File Report O-20-11, Natural hazard risk report for Lincoln County, Oregon, including the Cities of Lincoln City, Depoe Bay, Siletz, Newport, Toledo, Waldport, and Yachats, and the Confederated Tribes of Siletz Indians, and the unincorporated communities of Otis-Rose Lodge, Salishan-Lincoln Beach, Otter Rock, Seal Rock-Bayshore, and Wakonda Beach,
by Matt C. Williams, Christina A. Appleby, Lowell H. Anthony, and Fletcher E. O'Brien; 99 p. report, 7 tabloid size map plates, one Esri® geodatabase with internal metadata, external metadata in .xml format.

What's in this report?
This report describes the methods and results of a natural hazard risk assessment for Lincoln County communities. The risk assessment can help communities better plan for disaster.

Report downloads:

EXECUTIVE SUMMARY

This report was prepared for the communities of Lincoln County, Oregon, with funding provided by the Federal Emergency Management Agency (FEMA). It describes the methods and results of the natural hazard risk assessment performed in 2016-2018 by the Oregon Department of Geology and Mineral Industries (DOGAMI) within the study area. The purpose of this project is to provide communities within the study area a detailed risk assessment of the natural hazards that affect them to enable them to compare hazards and act to reduce their risk. The risk assessment contained in this project quantifies the impacts of natural hazards to these communities and enhances the decision-making process in planning for disaster.

We arrived at our findings and conclusions by completing three main tasks: compiling an asset database, identifying and using best available hazard data, and performing natural hazard risk assessment.

In the first task, we created a comprehensive asset database for the entire study area by synthesizing assessor data, U.S. Census information, Hazus-MH general building stock information, and building footprint data. This work resulted in a single dataset of building points and their associated building characteristics. With these data we were able to represent accurate spatial location and vulnerability on a building-by-building basis.

The second task was to identify and use the most current and appropriate hazard datasets for the study area. Most of the hazard datasets used in this report were created by DOGAMI; some were produced using high-resolution lidar topographic data. While not all the data sources used in the report are countywide, each hazard dataset was the best available at the time of writing.

In the third task, we performed the risk assessment using Esri® ArcGIS Desktop® software. We took two risk assessment approaches: (1) estimated loss (in dollars) to buildings from flood (recurrence intervals) and earthquake scenarios using FEMA Hazus®-MH methodology, and (2) calculated number of buildings, their value, and associated populations exposed to earthquake, flood, and tsunami inundation scenarios, or susceptible to varying levels of hazard from landslides, coastal erosion, and wildfire.

The findings and conclusions of this report show the potential impacts of hazards in communities within Lincoln County. A Cascadia Subduction Zone (CSZ) event (earthquake and tsunami) will cause extensive damage and losses throughout the county. Hazus-MH earthquake simulations illustrate the potential reduction in earthquake damage through seismic retrofits. Flooding is a threat for many communities in the study area, and we quantify the number of elevated structures that are less vulnerable to flood hazard. Our analysis shows that new landslide mapping based on improved methods and lidar information will increase the accuracy of future risk assessments. The risk from coastal erosion is high for many buildings along the open coast of Lincoln County. During the time of writing, the best available data show that wildfire risk is moderate for the overall study area. Our findings also indicate that most of the critical facilities in the study area are at high risk from a CSZ event (earthquake and tsunami). We also found that the two biggest causes of population displacement are a CSZ event (earthquake and tsunami) and landslide hazard. Lastly, we demonstrate that this risk assessment can be a valuable tool to local decision-makers.

Results were broken out for the following geographic areas:

Selected Study Area Results
Total buildings: 42,052
Total estimated building value: $5.1 billion
Cascadia Subduction Zone (CSZ)
Magnitude 9.0 Earthquake
a
Red-tagged buildingsb: 9,712
Yellow-tagged buildingsc: 3,562
Loss estimate: $1.2 billion
Cascadia Subduction Zone
Tsunami Inundation

Number of buildings exposed: 4,110
Exposed building value: $812 million
100-year Flood Scenario
Number of buildings damaged: 2,377
Loss estimate: $52 million
Landslide Exposure (High and Very High Susceptibility)
Number of buildings exposed: 12,894
Exposed building value: $1.4 billion
Coastal Erosion Exposure (Moderate Hazard)
Number of buildings exposed: 876
Exposed building value: $238 million
Wildfire Exposure (High Hazard)
Number of buildings exposed: 1,475
Exposed building value: $130 million
aResults reflect damages caused by earthquake to buildings outside of the tsunami zone. Earthquake and tsunami results combined estimate the total damages from a CSZ M9.0 event.
bRed-tagged buildings are considered to be uninhabitable due to complete damage.
cYellow-tagged buildings are considered to be of limited habitability due to extensive damage.

 


GEOGRAPHIC INFORMATION SYSTEM (GIS) DATA

Geodatabase is Esri® version 10.2 format.
Metadata is embedded in the geodatabase and is also provided as separate .xml formatted files.

Each dataset listed below has an associated, standalone .xml file containing metadata in the Federal Geographic Data Committee Content Standard for Digital Geospatial Metadata format.

Lincoln_County_Risk_Report_Data.gdb:
Feature dataset: Asset_Data:    
Building_footprints polygons .xml
Communities polygons .xml
UDF_points points .xml
Raster data: Hazard Data:    
FL_Depth_10yr grid .xml
FL_Depth_50yr grid .xml
FL_Depth_100yr grid .xml
FL_Depth_500yr grid .xml

 

APPENDIX E: MAP PLATES (PDFs, 17 x 11 inches each)

Plate 1, Building Distribution Map of Lincoln County, Oregon (6 MB PDF)


Plate 2. Population Density Map of Lincoln County, Oregon (6 MB PDF)


Plate 3. CSZ M9.0 Peak Ground Acceleration Map of Lincoln County, Oregon (5 MB PDF)


Plate 4. Tsunami Inundation Map of Lincoln County, Oregon (7 MB PDF)


Plate 5. Flood Hazard Map of Lincoln County, Oregon (6 MB PDF)


Plate 6. Landslide Susceptibility Map of Lincoln County, Oregon (6 MB PDF)



Plate 7. Wildfire Hazard Map of Lincoln County, Oregon (3 MB PDF)