DOGAMI OPEN-FILE REPORT SERIES

[Go back] | Publications Center | DOGAMI Home

PUBLICATION PREVIEW

 Open-File Report O-21-04, Natural hazard risk report for Coos County, Oregon, including the Cities of Bandon, Coos Bay, Coquille, Lakeside, Myrtle Point, North Bend, and Powers, and Tribal Lands of the Confederated Tribes of Coos, Lower Umpqua, and Siuslaw Indians and the Coquille Indian Tribe, and the unincorporated communities of Bunker Hill, Charleston, Glasgow, Green Acres, Hauser, and Millington,
by Matt C. Williams, Ian P. Madin, Lowell H. Anthony, and Fletcher E. O'Brien; 110 p. report, 7 tabloid size map plates, one Esri® geodatabase with internal metadata, external metadata in .xml format.

View Story Map 

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

Report downloads:

EXECUTIVE SUMMARY

This report was prepared for the communities of Coos 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 2018 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 and 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, and wildfire hazards.

The findings and conclusions of this report show the potential impacts of hazards in communities within Coos County. A Cascadia Subduction Zone (CSZ) event (earthquake and tsunami) will cause extensive damage and losses throughout the county. Our findings indicate that most of the study area’s critical facilities are at high risk to a CSZ event. We also found that the hazards with the highest potential of population displacement are earthquake, tsunami, and landslide hazards. 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. During the time of writing, the best available data show that wildfire risk is high for the upstream portions of the Coos River watershed. 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: 42,550
Total estimated building value: $11.5 billion

Cascadia Subduction Zone (CSZ)
Magnitude 9.0 Earthquakea

Red-tagged buildingsb: 9,689
Yellow-tagged buildingsc: 3,659
Loss estimate: $3.5 billion

Cascadia Subduction Zone
Tsunami Inundation

Number of buildings exposed: 1,286
Exposed building value: $612 million

100-year Flood Scenario
Number of buildings damaged: 1,870
Loss estimate: $125 million

Landslide Exposure (High and Very High Susceptibility)
Number of buildings exposed: 7,123
Exposed building value: $1.6 billion

Wildfire Exposure (High Hazard)
Number of buildings exposed: 1,050
Exposed building value: $217 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 Mw 9.0 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.

Coos_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 Coos County, Oregon (6 MB PDF)

Map

Description automatically generated

 

 

 

 

Plate 2, Population Density Map of Coos County, Oregon (5 MB PDF)

 

 

 

 

 

Plate 3, CSZ Mw 9.0 Earthquake Shaking Map of Coos County, Oregon (4 MB PDF)

 

 

 

 

 

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

 

 

 

 

 

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

 

 

 

 

 

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

 

 

 

 

 

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