DOGAMI OPEN-FILE REPORT SERIES

[Go back] | Publications Center | DOGAMI Home

PUBLICATION PREVIEW

 Open-File Report O-22-03, Multi-Hazard Risk Report for Wallowa County, Oregon, including the Cities of Enterprise, Lostine, Joseph, and Wallowa, by Matt C. Williams and Ian P. Madin; 63 p. report, 6 tabloid size map plates, two Esri® geodatabases 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 Wallowa County communities. The risk assessment can help communities better plan for disaster.

Report downloads:

EXECUTIVE SUMMARY

This report was prepared for the communities of Wallowa County, Oregon, with funding provided by the Oregon Department of Land Conservation and Development (DLCD). It describes the methods and results of natural hazard risk assessments performed in 2021 by the Oregon Department of Geology and Mineral Industries (DOGAMI). The purpose is to provide Wallowa County communities 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 risk assessments 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 Federal Emergency Management Agency (FEMA) Hazus®-MH methodology, and (2) calculated number of buildings, their value, and associated populations exposed to earthquake, and flood scenarios, or susceptible to varying levels of hazard from landslides and wildfire.

The findings and conclusions of this report show the potential impacts of hazards in communities within Wallowa County. An earthquake can cause a moderate amount of damage and losses throughout the county. Hazus-MH earthquake simulations illustrate the potential reduction in earthquake damage through seismic retrofits. Some communities in the study area have significant risk from flooding, 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 mapping. Wildfire risk is high for the majority the unincorporated county, as well as parts of Enterprise and Wallowa. Our findings also indicate that many of the critical facilities in the study area are at high risk from wildfire hazard. We also found that the two biggest causes of population displacement are wildfire 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 Countywide Results
Total buildings: 9,708
Total estimated building value: $910million

2500-year Probabilistic Magnitude 7.0 Earthquake 
Red-tagged buildingsa: 497
Yellow-tagged buildingsb: 1,515
Loss estimate: $114 million

100-year Flood
Number of buildings damaged: 295
Loss estimate: $1.5 million

Landslide (High and Very High-Susceptibility)
Number of buildings exposed: 568
Exposed building value: $67 million

Wildfire (High Risk)
Number of buildings exposed: 3,623
Exposed building value: $286 million

aRed-tagged buildings are considered to be uninhabitable due to complete damage.
bYellow-tagged buildings are considered to be of limited habitability due to extensive damage.  

 


GEOGRAPHIC INFORMATION SYSTEM (GIS) DATA

Geodatabases are Esri® version 10.7 format.
Metadata is embedded in the geodatabases 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.

Wallowa_County_Risk_Report_Data.gdb:

Feature dataset: Asset_Data:

 

 

Building_footprints

polygons

.xml

Communities

polygons

.xml

UDF_points

points

.xml


Wallowa_County_Depth_Grids .gdb:

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 Wallowa County, Oregon (5.5 MB PDF)

MapDescription automatically generated

 

 

Plate 2, Population Density Map of Wallowa County, Oregon (5.4 MB PDF)

 

 

Plate 3, 2,500-year Probabilistic Earthquake Shaking Map of Wallowa County, Oregon (2.8 MB PDF)

 

 

Plate 4, Flood Hazard Map of Wallowa County, Oregon    (5.6 MB PDF)

 

 

Plate 5, Landslide Susceptibility Map of Wallowa County, Oregon (7.7 MB PDF)

 

 

Plate 6, Wildfire Risk Map of Wallowa County, Oregon (6.4 MB PDF)