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Open-File Report O-20-15, Natural Hazard Risk Report for Curry County, Oregon, including the Cities of Brookings, Gold Beach, Port Orford and Unincorporated Communities of Harbor and Nesika Beach,
by Matt C. Williams and Lowell H. Anthony; 82 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 Curry County communities. The risk assessment can help communities better plan for disaster.

Report downloads:

EXECUTIVE SUMMARY

This report was prepared for the communities of Curry 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 by the Oregon Department of Geology and Mineral Industries (DOGAMI) within the study area. The purpose of this project was to provide communities with a detailed understanding of their risk from natural hazards, to give communities the ability to compare their risk across multiple hazards, and to prioritize and take actions that will reduce risk. The results of this study can also inform the natural hazard mitigation planning process.

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.

To complete 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. Using this dataset, 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 the analysis was performed.

In the third task, we performed the risk assessment using Esri® ArcGIS Desktop® software. We used 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, tsunami, flood, landslides, coastal erosion, and wildfire hazards.

The findings and conclusions of this report show the potential impacts of hazards in communities within Curry County. A Cascadia Subduction Zone (CSZ) event (earthquake and tsunami) will cause extensive damage and losses throughout the county. Our findings also indicate that most of the study area’s critical facilities are at high risk to a CSZ event. We also found that the two biggest causes of population displacement are a CSZ event (earthquake and tsunami) and landslide hazard. We demonstrate the potential for the reduction in damages and losses from seismic retrofits through building code simulations in the Hazus-MH earthquake model. Flooding is a threat for some 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 higher for the community of Nesika Beach than others part of Curry County. During the time of writing, the best available data show that wildfire risk is moderate for the overall study area. Lastly, we demonstrate that this risk assessment can be a valuable tool for local decision-makers.

Results were broken out for the following geographic areas:

Selected Study Area Results
Total buildings: 20,767
Total estimated building value: $1.6 billion
Cascadia Subduction Zone (CSZ)
Magnitude 9.0 Earthquake
a
Red-tagged buildingsb: 5,924
Yellow-tagged buildingsc: 2,277
Loss estimate: $451 million
Cascadia Subduction Zone
Tsunami Inundation
(Medium-sized)
Number of buildings exposed: 1,755
Exposed building value: $169 million
100-year Flood Scenario
Number of buildings damaged: 410
Loss estimate: $5.9 million
Landslide Exposure (High and Very High Susceptibility)
Number of buildings exposed: 3,969
Exposed building value: $309 million
Coastal Erosion Exposure (Moderate Hazard)
Number of buildings exposed: 107
Exposed building value: $19 million
Wildfire Exposure (High Hazard)
Number of buildings exposed: 303
Exposed building value: $25 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.

Curry_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 Curry County, Oregon (6 MB PDF)


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


Plate 3. M9.0 CSZ Peak Ground Acceleration Map of Curry County, Oregon (4 MB PDF)


Plate 4. Tsunami Inundation Map of Curry County, Oregon (6 MB PDF)


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


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



Plate 7. Wildfire Hazard Map of Curry County, Oregon (6 MB PDF)