This report was prepared for communities in Crook County, Oregon, with funding provided by the Federal Emergency Management Agency (FEMA). It describes the methods and results of a natural hazard risk assessment performed in 2024 and 2025 by the Oregon Department of Geology and Mineral Industries (DOGAMI) for Crook County (herein referred to as the study area). The purpose of this project is to provide communities with detailed risk assessment information to enable them to understand and compare hazards on a community-by-community basis and act to reduce their risk. The risk assessment results quantify the consequences of natural hazards to each community by estimating the number of people and buildings at risk and support the decision-making process in planning for disaster. Also included in this study is an inventory of bridges and dams in the county along with their level of risk from natural hazards.

This study includes an update to the Seismic Safety Needs Assessment database developed by DOGAMI in 2007. The original database was compiled through site inspection of critical facilities across the state and assessing them for their seismic vulnerability using FEMA's Rapid Visual Screening methodology. For this study, DOGAMI staff reassessed Crook County's critical facilities and added any new critical facilities that had been built after the initial assessment in 2007.

The authors arrived at these results and conclusions by completing three main tasks: compiling an asset database, identifying and using the best available hazard data, and performing a natural hazard risk assessment. In the first task, the authors created a comprehensive asset database for Crook County by synthesizing assessor data, U.S. Census information, Federal Emergency Management Agency (FEMA) Hazus®-MH general building stock information, and building footprint data. This work resulted in a single dataset of building points and their associated characteristics (e.g., construction materials, number of floors, usage). Using these data, the authors represented accurate spatial locations and vulnerabilities on a building-by-building basis. The study also estimated the number of residents occupying residential structures to approximate the number of people that might be at risk to a given hazard.

The second task was to identify and use the most current and appropriate hazard datasets for the study area. The significant natural/geologic hazards affecting Crook County include flooding, earthquakes, landslides, and wildfires. Most of the hazard datasets used in this report were produced by DOGAMI scientists using peer-reviewed methods and lidar (high-resolution topographic data). Although not all the data sources used in the report provide complete, countywide information, each hazard dataset used was the best available at the time of the analysis. Data sources and coverage are discussed in detail for each hazard in Section 3.0 Assessment Overview and Results.

In the third task, the authors analyzed risk using Esri® ArcGIS Desktop® software. The study presents two risk assessment approaches, depending on the nature of the hazard data: (1) estimating building losses (in dollars) for floods and earthquakes using the Hazus methodology and (2) calculating the 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. Details on recurrence intervals, susceptibility, hazard levels, and other particulars are discussed for each hazard in Section 3.0 Assessment Overview and Results.

The findings and conclusions of this report indicate the wide range of potential impacts hazards could have on the communities of Crook County. A Southeast Newberry Fault earthquake scenario is expected to cause slight damage and losses throughout the county, with losses in the region of $53 million (see results summary below). The authors demonstrate the potential for reduction in earthquake damages and losses through seismic retrofits using building code simulations in the Hazus earthquake model. Flooding in Prineville can be expected to cause relatively small amounts of damage to low-lying homes and businesses. Study results estimate ~300 buildings will be affected, with potential losses in the region of $5 million. Notably, 231 structures are elevated above 100-year-flood levels and accordingly are less vulnerable to flood hazards. Analysis of landslide susceptibility demonstrates that areas with moderate to steep slopes or at the base of steep hillsides are at the greatest risk from landslide hazards. Landslides thus have the potential to result in damages totaling ~$180 million; areas of highest risk are in the unincorporated areas surrounding Prineville. Wildfire exposure analysis shows a high risk for buildings in the Wildland Urban Interface (WUI) surrounding Prineville, including 3 of 22 critical facilities. Total losses for wildfire could reach ~$570 milion. The highest potential for population displacement is associated with wildfire hazards (~3,400).  

Results were broken out for the following geographic areas:

• Unincorporated Crook County (rural)
• Community of Powell Butte
• Community of Juniper Canyon
• City of Prineville

Selected countywide results are based on a total of 19,978 buildings and total estimated building value of $5 billion; results are summarized below.

• Southeast Newberry Fault Magnitude (Mw) 7.2 earthquake scenario:
• Red-tagged buildings: 41
• Yellow-tagged buildings: 215
• Loss estimate: $53 million
• Landslide exposure (high and very high susceptibility):
• Number of buildings exposed: 882
• Value of total number of exposed buildings: $177 million
• 100-year flood scenario:
• Number of buildings damaged: 302
• Loss estimate: $5 million
• Wildfire exposure (high burn probability):
• Number of buildings exposed: 3,103
• Exposed building value: $573 million