Section Purpose

The purpose of the State Natural Hazards Risk Assessment is to identify and characterize Oregon's natural hazards, and assess the risk to communities from those hazards. This web-based report is one of the many components that work together to make up the state Natural Hazards Mitigation Plan pursuant to 44 CFR Parts 201.4 and 201.5, and will be used by the State Interagency Hazards Mitigation Team to determine priorities for selecting and implementing future mitigation measures.

This section of the plan:

• Broadly identifies and describes the natural hazards that Oregon faces, while highlighting previous plans, assessment tools and resources that have been developed to identify, profile and assess the vulnerability of Oregon risk from natural hazard events;
• Profiles regional hazard events to provide an overview of the location of all natural hazards that can affect the state, including information on previous occurrences of hazard events and probability of future events;
• Locally assesses the vulnerability to the natural hazards, based on a hazard analysis methodology developed by FEMA and modified by OEM.  Each of Oregon’s counties has completed a local hazard analysis using this methodology; and
• Provides an overview and analysis of the state’s vulnerability to hazards.  It describes vulnerability in terms of the jurisdictions most threatened by the identified hazards, and most vulnerable to damage and loss associated with hazard events.

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Oregon's Natural Hazards: Hazards Identified, Profiled and Assessed

This section describes the natural hazards that Oregon faces. A brief overview of the hazard is provided as well as a link to a detailed hazard chapter that fully describes the hazard and lists short and long-term action items. The brief overview includes a description of the hazard, an overview of Oregon’s vulnerability to natural hazards, and a list of additional resources about the hazard.

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State's Natural Hazards Viewer

The State’s natural hazard viewer is an online interface to provide information about the hazard risk throughout the state. The data is periodically compiled from regional representatives and entered into a database that is linked to the maps provided in the viewer.

As part of their hazard analysis, each county develops risk scores for the hazards they face, including Oregon’s seven major natural hazards shown in this hazard viewer.  These scores range from 24 (low) to 240 (high), and reflect the county’s perceived risk for each particular hazard. To create the hazard rating score, Oregon Emergency Management refined a FEMA methodology for local hazard analyses. Vulnerability and probability are the two key components of the methodology.  Vulnerability examines both typical and maximum credible events, and probability endeavors to reflect how physical changes in the jurisdiction and scientific research modify the historical record for each hazard.  Vulnerability accounts for approximately 60% of the total score, and probability approximately 40%.  By using this methodology consistently throughout the state, one can compare the risk posed by a particular hazard from one county to the next, and each local jurisdiction can compare one hazard against others to establish priorities for planning, capability development, and hazard mitigation.

Once all the counties developed the scores for each hazard, the scores can be classified into risk categories (e.g. High Risk). These categories, or classes, are generated through what is known as "equal-interval" classification, for which each risk category represents an equal range of the original scale. For example, in the case of a six-class map, the Low Risk category represents the bottom sixth of the range or 24 to 60, and the High Risk category represents the top sixth of the range from 204 to 240. By changing the number of classes on the map, you can see the overall pattern (few classes) or regional variations (many classes).

The maps reflect the reported raw scores for each county based on a partially subjective ranking of each hazard.  Because the ratings are reported as the relative risk of a hazard within a county, and because each county conducted the analysis with a different team of people working with slightly different assumptions, comparing scores between counties must be treated with caution.

View the  State’s Natural Hazards Viewer

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Regional Natural Hazards Risk Assessment

The purpose of the regional natural hazards risk assessment is to identify and characterize Oregon's natural hazards and assess the risk to communities from those hazards.  The state has been divided into eight regions for the purpose of the assessment. Each region description includes:

A. Overview: The brief overview includes a description of the hazard, an overview of Oregon’s vulnerability to natural hazards, and a list of additional resources about the hazard.

B. Regional Maps: Infrastructure maps provide information about the general location of schools, hospitals, bridges, power stations, and dams.

C. Regional Profile: Using the best and readily available data, the regional profile briefly summarizes and describes the population and demographics, economy, development trends, transportation and critical infrastructure. Primary data sources for the regional profiles included Oregon Employment Department's 2002 Regional Profiles, the 2000 US Census, Oregon Economic Community Development Department, and the Department of Land Conservation and Development.

D. Natural Hazard Assessment: The regional natural hazard assessment section describes historical impacts, general location, extent, and severity of past natural hazard events as well as the probability for future events. These assessments were based on best available data related to historical events, repetitive losses, local county hazards rankings and general development trends.

Link to a detailed hazard chapter that fully describes the hazard and lists short and long-term action items.

View and/or download the Regional Natural Hazards Risk Assessment

Infrastructure Overview

To obtain an overview of Oregon’s vulnerability to various disasters, the following maps (Click here to view State Infrastructure Maps) from the Atlas of Oregon display a wealth of information describing Oregon’s major population centers, the major transportation networks, and a snapshot of the key employment and manufacturing centers located in various parts of the state.  Because of Oregon’s size and its physiographic diversity, a disaster occurring in one part of the state may be traumatic to that region while having minimal effect on the state as a whole, or a disaster that cripples the northern Willamette Valley could be devastating to the entire state.  Therefore, to get a sense of Oregon’s vulnerability, one should compare the information on these maps with the hazard analysis information provided in the plan for the eight regions of the state.

The first map from the Atlas of Oregon is titled “Population and Transportation.”  Through “color-coding,” it displays Oregon’s major population centers and the state’s overall population density ranging from the high density areas of the Willamette Valley to the very low density areas of southeastern Oregon.

This map also displays the state’s vast highway system connecting the eight regions of the state.  Displayed in blue on the map are the two interstate highways, I-5 traversing north and south connecting Oregon with the states of California and Washington.  I-84 connects to I-5 in Portland and serves a portion of the Northern Willamette, the Mid-Columbia, and Northeast Regions of the state before connecting with the state of Idaho to east.

There are also two additional north-south routes serving regions of the state that parallel I-5.  US Highway 101 serves the entire Coast-Lower Columbia region connecting California and the city of Brookings in the south to the city of Astoria before crossing into the state of Washington to the north.  The other main route is US Highway 97 that runs from California and the city of Klamath Falls through cities of Bend, Redmond and Madras, located in the Central Oregon Region, and connecting to I-­84 at Biggs Junction, located in the Mid-Columbia Region, before crossing the Columbia River into Washington State.

The map also displays eight highways that connect I-5 with US Highway 101, and six highways that connect I-5 with US Highway 97.  All of these connecting highways provide passage over or around the Coast Range or Cascade Range of mountains that separate many of Oregon’s regions.  These routes often provide a challenge for travelers during the winter with some routes occasionally blocked by winter storms or landslides.

The Population and Transportation map also displays Oregon’s seven major airports that link Oregon with the nation’s air transportation system.  Of greatest importance to Oregon is the Portland International Airport.  Because of its location adjacent to the Columbia River and its proximity to the Columbia River Gorge, the Portland International Airport is vulnerable to severe winter (ice) storms that are relatively common disasters that affect this region.

The next map from the Atlas of Oregon is titled “The Economy.”  Besides providing an overview of Oregon’s economy, this map identifies the various economic centers located throughout the state.  The city of Portland and the numerous cities in the Portland metropolitan area, provide the greatest contribution to Oregon’s economy.  The Portland metropolitan area is located in the Northern Willamette Region.  The Mid/Southern Willamette Region is also a significant contributor to Oregon’s economy.  This region includes some of Oregon’s largest cities, Salem, the state capital, Eugene, Corvallis and Albany.  Other areas of the state that are significant contributors to Oregon’s economy are generally located along the I-5 and I-84 corridors and on US Highways 97 and 101.

By looking carefully at this map and by reviewing the Regional Profiles provided in this plan, it is apparent that specific types of hazards can affect regions of the state differently.  For example, a major wildfire could have a greater impact on southern Oregon’s economy, where wood products and agriculture are significant contributors to this region’s economic base, than in the Northern Willamette Region, which is less dependent on resource-based industries.  On the other hand, a major earthquake centered in the Northern Willamette Region could severely damage that region’s economy while an earthquake of the same magnitude would have less of an impact if it occurred in a sparsely populated, more resource-dependent region of the state.

With the information displayed on these maps and the hazard analysis information provided for the eight regions of the state, assumptions can be been made regarding the impact certain types of disasters may have on Oregon and the state’s ability to recover.  A more detailed discussion of the effects certain disasters may have on Oregon’s economy and infrastructure and the assumptions used to support the plan’s overall conclusions can be found later in this plan.

View the State Natural Hazards Risk Assessment

Download a PDF copy of the State's Population, Transportation and Economy maps

Download a PDF copy of the State's Power and Energy Distribution maps

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Overall Vulnerability

Oregon is vulnerable to many natural hazard events.  For the purpose of assessing Oregon’s overall vulnerability to natural hazards, hazardous events were placed into two categories: catastrophic and chronic.  Where such events occur is a major factor in determining Oregon’s vulnerability. The most vulnerable region of the state is the Portland metropolitan region because it’s the most densely populated area in the state (approx. 1.5 million people).  In addition, it has number of critical facilities and infrastructure serving the region, and its overall importance to the state’s economy.

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Catastrophic Disasters

The three most potentially catastrophic disasters most likely to occur in Oregon are a major subduction zone earthquake, a locally-generated tsunami, or a volcanic eruption.  Of these three, a major earthquake (M 8-9) with its epicenter in the Pacific Ocean immediately adjacent to the Oregon coast (likely to be followed by tsunamis hitting the Oregon coast) would be the most devastating natural disaster in terms of loss of life, damage to state facilities, buildings and infrastructure, and its overall impact on the state’s economy.  Such an event would be catastrophic immediately after the disaster and the region’s recovery would be very difficult, expensive and long-term.

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Chronic Hazards

Oregon has a number of natural hazards that occur frequently: windstorms, wildfires, winter storms, flooding and landslides occur somewhere in Oregon every year. However, any one of these hazardous events can become a major disaster if it impacts one or more of Oregon’s population centers. The most likely natural hazards to occur and impact a large number of Oregonians are flooding, windstorms, wildfires and winter storms.

Certain areas within Oregon are more susceptible to one of these four chronic hazards than other areas in the state.  Tillamook County in the Coast/Lower Columbia Region is the most vulnerable to flooding which typically occurs during the autumn and winter months.  Major windstorms also occur during the autumn and winter months, and can impact one or more of the seven counties along the Oregon coast.  The Southwest and Central Oregon Regions are the most vulnerable to wildfires typically occurring during the late summer.  Although they do not occur every year, winter ice storms have the greatest impact on the Columbia River Gorge area and in particular, the east Multnomah County portion of the North Willamette Region.

Download a PDF copy of the State's Volcanoes, Landslide and Earthquake maps

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Estimating Potential Losses to State Facilities

The state of Oregon has prepared the following analysis of state owned and managed facilities.  This analysis is a first step at assessing which state owned structures are most vulnerable to the various hazards identified by region.  From this overview, it is clear that a more detailed assessment in the future will yield a clearer picture of those structures specifically threatened by certain disasters and the potential damage that may occur.

Using the Matrices

The methodology used in developing the following eight matrices involves comparing the list of state structures obtained from the Department of Administrative Services against the levels of risk, as determined by each county, for eight of the natural hazards contained in the “Regional Hazard Viewer” (2004) prepared by the University of Oregon InfoGraphics Lab.  More detailed information about each hazard and the potential risk to facilities located within each region can be obtained from the Regional Profiles of the eight regions.  The Regional Profiles contain assessments of the risks, vulnerabilities and potential losses in dollars to Oregon’s key facilities and infrastructure.

There is one spreadsheet (matrix) for each of the following regions:  Coast/Lower Columbia; Northern Willamette; Mid/Southern Willamette; Southwest; Mid-Columbia; Central; Northeast; and Southeast.  Each regional spreadsheet groups facilities by county using a specific color. Click here to download a PDF of the guide on how to read the matrices.

State Facilities Table