 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||
|
|
Oregon's Regional Natural Hazard Risk Assessment
The purpose of this web-based document is to identify and characterize Oregon's natural hazards and assess the risk to communities from those hazards. Additionally, 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. This document covers the following:
a.) Regional Maps
b) Regional Profile - Using the best readily available data, the regional profile briefly summarizes and describes population and demographics, economy, development trends, transportation and critical infrastructure. Primary data sources for the regional profiles include Oregon Employment Department's 2002 Regional Profiles, the 2000 US Census, and data from Oregon Economic and Community Development Department and the Department of Land Conservation and Development. c.) Regional Natural Hazard Risk Assessment - The regional natural hazard risk 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, county hazard analysis rankings, and general development trends. d.) Regional State Facilities tables - The state of Oregon has prepared an 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. The State Natural Hazards Risk Assessment adds to the current body of literature and technical resource guides available to Oregon communities. (Please refer to the documents on the side bar for a listing of natural hazard mitigation resources.) The three levels of government - federal, state, and local - will find this document useful when assessing natural hazards and planning mitigation activities. Local governments can use the document in the development of their jurisdiction's natural hazards mitigation plan. Information from the regional profiles can be used as a springboard for more detailed community profiles. Index Region 1: Oregon Coast Region 2: Northern Willamette Valley/Portland Metro Region 3: Mid/Southern Willamette Valley Region 4: Southwest Oregon Region 5: Mid-Columbia Region 6: Central Oregon Region 7: Northeast Oregon Region 8: Southeast Oregon Region 1, Oregon Coast: Regional Profile Overview  The Oregon Coast region has experienced an 8% increase in population since 1990. This represents a lower rate of growth than other regions of the state. Just over half of the region's population lives in incorporated areas. Thirty percent of the region's houses were built before 1960, 35% between 1960 and 1980, and 35% were built after 1980. Transportation networks are an important consideration for the coastal region given the physical boundary of the ocean to the west and the Coast Range to the east. The average commute for workers in this region is 22 minutes each way. Seventy-five percent of the region's workers drive alone to work, 13% carpool, 5% work from home, 4% walk, and another 3% use other means to travel to work. Most bridges in the area have not been seismically retrofitted, creating significant risk to the commuting population from earthquakes. Historically, the fishing, lumber and wood products industries dominated this region, but those industries have been surpassed by service sector jobs and retail. The median income for residents of region 1 in 2000 was $31,955. This is below the national average of $41,433 and the state's average of $40,916.Regional Hazard Assessment Overview Region 1 has a high probability of being affected by a tsunami, earthquake, flooding, landslides, wildfire, or windstorms. It has a low probability of being impacted by volcanic hazards. The geographical position of Region 1 makes it highly vulnerable to earthquakes from several sources, but the off-shore Cascadia Subduction Zone could cause the greatest damage. The last large earthquake recorded - though not a subduction event - was a magnitude 7.3 in 1873 with an epicenter near the City of Brookings. Tsunamis typically occur as secondary hazards to earthquakes, or occasionally due to underwater landslides. In 1964, Cannon Beach, Coos Bay, Depoe Bay, Florence, Gold Beach, and Seaside were struck by a tsunami generated in Alaska, thereby incurring over half a million dollars in damage and resulting in four fatalities. In Region 1 there can be a moderate to high level of vulnerability to tsunamis below 100 feet MSL. High winds can be expected throughout Region 1. Gusts exceeding 100 miles per hour are fairly common at several coastal locations during winter storms. The most famous of these storms is the 1962 Columbus Day storm that had recorded winds over 130 mph on the coast and resulted in 23 fatalities. The vulnerability to windstorms in the region is high to moderate, mitigated to some extent by building code provisions that account for high winds. Three types of flooding occur in this region: riverine, ocean flooding from high tides and wind-driven waves, and flooding associated with a tsunami event. Repetitive flood events have impacted the City of Tillamook, exceeding the base flood elevation numerous times, including 1996, 1998 and 1999. FEMA later re-mapped the floodplain in the City of Tillamook, and the 100-year base flood elevation is higher in some areas along north Highway 101. Most of the counties in Region 1 have a high probability of flooding. Heavy rainstorms also typically cause landslides. The vulnerability to landslides is high to moderate. Region 1 is less vulnerable to drought impacts than most of Oregon, but droughts can still be problematic, especially given that they often precede major wildfires. Severe drought conditions resulted in the four disastrous Tillamook fires (1933, 1939, 1945, 1951), collectively known as the Tillamook Burn. There have been a number of long droughts throughout the last century, as well as a drought during 2001. While the region's vulnerability to drought is low, its vulnerability to wildfire is considered high to moderate. For more information on previous occurrences of hazard events, as well as the probability of future hazard events as estimated in local risk assessments, download the full regional profile. Region 1 Report Downloads (Oregon Coast / Lower Columbia): Clatsop, Tillamook, Lincoln, Coastal Lane, Coastal Douglas, Coos, and Curry counties (in order from north to south)
Region 2, Northern Willamette Valley/Portland Metro: Regional Profile Overview  Region 2 is made up of four counties: Columbia, Washington, Multnomah, and Clackamas. Encompassing the Portland metropolitan area, the Northern Willamette region is home to nearly half of the state's population. In 2000, the population of the region had increased 19% since 1990. Seventy-three percent of the region's population lives in incorporated areas and 27% live in unincorporated areas. The older the house, the greater risk from damage from natural disaster, and 30% of the region's housing was built before 1960. Thirty-four percent were built between 1960 and 1980, and 36% after 1980. Transportation networks are another important consideration in hazard mitigation. In very dramatic fashion, flooding and landslides (which occur frequently in this region) can impact roads, bridges and railways. The average commute for workers in the region is 25 minutes each way. Seventy-one percent of workers in this region drive alone to work, 11% carpool, 8% use public transportation, and 5% walk to work or commute in another way. Five percent work at home. Most bridges in the area have not been seismically retrofitted, creating significant risk to the commuting population from earthquakes. Looking towards the future, the high tech. industry, electronics, transportation, metals, healthcare, administrative, finance and retail trade sectors will continue to provide goods, services and work opportunities for the area residents. The median income for the region was $47,569 in 2000. This is well above the national average of $41,433 and the state's average of $40,916.Regional Hazard Assessment Overview: Region 2 has a high probability of being affected by an earthquake, flooding, landslides in parts of the region, and high winds. There is a moderate probability of being struck by wildfire and drought. The counties in this region are subject to volcanic hazards from the Cascade Range. The risk posed by these hazards is greater in the mountainous portions of Clackamas and Multnomah counties. The geographic position of Region 2 makes it susceptible to earthquakes from several sources, including the off-shore Cascadia Subduction Zone. In March of 1993, the Scotts Mills earthquake caused damage in Regions 2 and 3. Region 2 is highly vulnerable to future earthquakes.. The Northern Willamette Valley has had a lengthy flood history, due in large part to flooding on the Willamette and Columbia Rivers. In 1996, warm temperatures melted snow in the mountains while record-breaking rains fell throughout the region; the combination of these events resulted in widespread flooding. The vulnerability to future flooding is moderate. Landslides often also result from heavy rainfall. In February 1996, landslide activity in Portland and East Multnomah County severely impacted homeowners and transportation routes. Vulnerability to landslides is variable and problematic throughout the region. High winds, sometimes associated with winter storms, can affect the region. The most persistent high winds in Region 2 occur in East Multnomah County.. Because some parts of the region contain extensive forested land in the wildland-urban interface (WUI) risk to developed and developing areas to wildfire is moderate to high. Though there has not been a large fire in the area since 1902, there are many areas in Region 2 where a large WUI fire could occur. Though, overall, the probability of a volcanic event occurring in Region 2 is low, all of the counties in the region are vulnerable to one volcanic hazard or another. Region 2's infrastructure and population would almost certainly be impacted by a volcanic eruption in the area. The eruption of Mt. Saint Helens in 1980 reminded people of the dangers of the volcanoes in the Cascade Range. For more information on previous occurrences of hazard events, as well as the probability of future hazard events as estimated in local risk assessments, download the full regional profile. Region 2 Report Downloads (Northern Willamette): Clackamas, Columbia, Multnomah, and Washington counties
Return to Index Region 3, Mid/Southern Willamette Valley: Regional Profile Overview:  Region 3 is composed of Benton, Lane (the non-coastal portion), Linn, Marion, Polk, and Yamhill counties. Between 1990 and 2000, the population of Region 3 increased by approximately 19%. This rapid growth rate is projected to continue over the next 20 years. Seventy percent of the region's population lives in incorporated areas. Twenty-eight percent of the region's housing was built before 1969, 39% was built between 1960 and1980, and 33% was built after 1980. Transportation networks are an important consideration in hazard mitigation. The impact of a disaster can disrupt automobile traffic and shut down local transit systems across the region, making evacuations difficult. The average commute for workers in the region is 22 minutes each way. Seventy-five percent of workers in this region drive alone to work, 13% carpool, 6% walk to work, and only 1% use public transportation. Five percent work at home. Most bridges in the area have not been seismically retrofitted, creating significant risk to the commuting population from earthquakes. In Region 3, the median household income is $40,516 annually, which is lower than the State of Oregon's median household income of $40,916. The region's economy has experienced a transition from lumber and wood production to a service-based economy.Regional Hazard Assessment Overview: The natural hazards with the highest probability of occurrence in the region are wildfire, flood, windstorms, and winter storm events. The probability of an earthquake impacting the region ranges from high to moderate chance of occurrence. The region's vulnerability to earthquakes is high. The region also has a moderate vulnerability to wildfires. In the recent past, wildfires that burned in the wildland-urban interface include the 1972 fire in Yamhill County that was the second time the Conflagration Act was invoked in Oregon history, and the 1987 Shady Lane Fire in Polk County that was declared both a Conflagration and also for FEMA Fire Suppression Assistance. Vulnerability to flood events in the region is variable, ranging from moderate to high. Past flood events have greatly impacted this region; the 1996 floods were the most notable recent events. Region 3's vulnerability to windstorms is high. A significant windstorm occurred in 2002, causing significant damages and impacts throughout the southern part of this region. The region also has a high vulnerability to winter storms. Recent winter storms of significance include the storms of 1985, 1998/1999, and 2003/2004. In 1985, massive power failures resulted when snow-laden tree limbs fell on power lines. The 1998/1999 storm occurred during one of the snowiest winters in Oregon history. For more information on previous occurrences of hazard events, as well as the probability of future hazard events as estimated in local risk assessments, download the full regional profile. Region 3 Report Downloads (Mid/Southern Willamette): Benton, Lane (non-coastal), Linn, Marion, Polk, and Yamhill counties
Return to Index Region 4 - Southwest Oregon Regional Profile Overview:  Region 4 is composed of Douglas (the non-coastal portion), Jackson, and Josephine counties. The Southwest Oregon region has experienced an 18% increase in population since 1990. The region is projected to grow at a moderate rate over the next 20 years. The region's population is almost equally divided between incorporated and unincorporated areas. Twenty-seven percent of the region's houses were built before1960, 37% between 1960 and 1980, and 36% were built after 1980. The impact of disaster can disrupt automobile traffic and shut down local transit systems across the region, making evacuation difficult. The average commute for workers in this region is 20 minutes each way. Seventy-seven percent of the region's workers drive alone to work, 11% carpool, 1% use public transportation, and another 5% walk or travel to work in another way. Six percent work at home. Most bridges in the area have not been seismically retrofitted, creating significant risk to the commuting population from earthquakes. In Region 4, median household income is $34,269 annually, which is lower than the State of Oregon's median household income of $40,916. The economy has experienced a transition from the timber and wood products industry to one that is service-based.Regional Hazard Assessment Overview: The natural hazards that have the highest probability of occurrence in the region are drought, wildfire, flooding, landslides, windstorms, and winter storms. The region is highly vulnerable in the event of earthquakes, wildfires, flooding, windstorms, and winter storms occurring. Droughts can affect the entire State of Oregon; in Region 4 the overall vulnerability is moderate. A significant drought occurred in 2001. Agricultural production was seriously impacted. Wildfires, often associated with droughts, are also a concern for the region. Vulnerability to wildfires is high because of the number of homes in the wildland-urban interface. The largest single fire in the recorded history of the state - the Biscuit Fire - occurred in Josephine County during 2002. Along with portions of the fire that burned in Curry County (Region 1) and California, the fire eventually grew to encompass 500,000 acres. The region has high vulnerability to flood events. Landslides, often associated with the rainfall that causes flooding, is also a concern. The region's vulnerability to landslides is moderate. Region 4 also has a high vulnerability to windstorms. A significant windstorm occurred in 2002 in Douglas County that included downed power lines and damage to buildings. Winter storm vulnerability in the region is also high. Recent winter storms of significance occurred in 1985 and 1998/1999. In 1985 massive power failures were a result of tree limbs falling on power lines. The 1998/1999 storm occurred during one of the snowiest winters in Oregon history. Region 4 is moderately vulnerable to earthquakes from several sources, including a Cascadia Subduction Zone event of magnitude 8.0 - 9.0. For more information on previous occurrences of hazard events, as well as the probability of future hazard events as estimated in local risk assessments, download the full regional profile. Region 4 Report Downloads (Southwestern Oregon): Douglas (non-coastal), Jackson, and Josephine counties
Return to Index Region 5 - Mid-Columbia Regional Profile Overview:  Region 5 is composed of Gilliam, Hood River, Morrow, Sherman, Umatilla and Wasco counties. The Mid-Columbia region has experienced a 19% increase in population since 1990. This growth pattern is projected to continue at a moderate rate over the next 20 years. Sixty percent of the region's population lives in incorporated areas with the other 40% living in unincorporated areas. Forty-three percent of the region's houses were built before 1960, 32% between 1960 and 1980, and 25% were built after 1980. The impact of a disaster can disrupt automobile traffic and shut down local transit systems across the region, making evacuation difficult. This is particularly important in this region where hazardous materials are being transported along Interstate 84 and nearby railroad lines. The average commute for workers in this region is 19 minutes each way. Seventy-six percent of the region's workers drive alone to work, 13% carpool, 6% walk or use other means, and 5% work at home. Most bridges in the area have not been seismically retrofitted, creating significant risk to the commuting population in areas at risk from earthquakes. In Region 5, the median household income is $36,135 annually, which is lower than the State of Oregon's median household income of $40,916. The economic base of the region is experiencing a transition from timber and wood products and aluminum industries to a service-based economy. Agriculture, especially wheat, is also a significant contributor to the economic base of the region.economy.Regional Hazard Assessment Overview: In Region 5, drought, wildfire, flooding, windstorms and winter storms have the highest probability of occurrence. The region is highly vulnerable in the event of drought, windstorms, and winter storms occurring. Drought is a major concern for Region 5. The most recent drought occurred during 2001, which was generally a dry period for the entire state. Wildfire, often associated with drought, is another concern; vulnerability to this hazard is moderate. Significant fires in the recent past occurred in the years 1998 and 2000, during which the Willow Creek Fire burned 27,000 acres in Morrow and Gilliam counties, and the Reith Barnhard/Coombs Canyon Fire burned 45,000 acres in Umatilla County. The region has a high vulnerability to windstorms, especially related to persistent high winds along the Columbia Gorge. Windstorms in the past that affected the region occurred in 1991 and 1995, during which high winds damaged wheat fields. The region's vulnerability to winter storms is also high. Recent significant winter storms occurred in 1998/1999, which was one of the snowiest winters in Oregon history, and also in 2003/2004. The latter closed I-84 for several days. The region is moderately vulnerability to flooding. In 1996, warm rain melted snow in the mountains, raising water levels in streams and rivers throughout the state. Additionally, the region has a moderate vulnerability to volcanic-related hazards, though the probability of the hazard affecting the region is low. For more information on previous occurrences of hazard events, as well as the probability of future hazard events as estimated in local risk assessments, download the full regional profile. Region 5 Report Downloads (Mid-Columbia): Gilliam, Hood River, Morrow, Sherman, Umatilla, and Wasco counties
Return to Index Region 6, Central Oregon Regional ProfileOverview:  Region 6 consists of Crook, Deschutes, Jefferson, Klamath, Lake, and Wheeler counties. Population in the region grew by 34% from 1990 to 2000, two and a half times faster than the state overall. Deschutes County has become the fastest growing county in the state. Slightly more than half of the region's population lives in unincorporated areas. Thirty percent of the houses in the region were built before 1960, 34% between 1960 and 1980, and 36% were built after 1980. The median household income in the central Oregon region in 2000 was $33,747, which is below the state and national levels. The recreation and tourism industries have helped to create new jobs in Crook, Deschutes, and Jefferson counties. The service, retail, tourism, healthcare, construction, and manufacturing industries are expected to continue to grow in the future. Recent population growth has led to an increase in traffic and commuting. The average commute time for workers in the region is 20 minutes each way. Seventy-five percent of the region's workers drive alone to work. Most bridges in the area have not been seismically retrofitted, creating significant risk to the commuting population in areas at risk from earthquake. Critical facilities, those facilities essential to government response and recovery activities, have been inventoried for each county.Regional Hazard Assessment Ovrview: Throughout Region 6, there is high probability for the occurrence of drought, wildland-urban interface fires, winter storms, and windstorms. The average recurrence interval for severe drought is between eight to twelve years. Severe winter storms occur about every 13 years, causing heavy snows in the Cascade Mountains, and sometimes at lower elevations in Region 6. The probability of flooding is high in Crook, Klamath, and Lake counties. In 1998, a federal disaster was declared in Crook County due to loss of the ability to deliver agricultural irrigation water, damage to the facilities within the irrigation district, and damage to approximately 100 homes. The probability of earthquake events ranges from moderate to low in the region. The probability of other hazards, including landslide and volcanic events, is generally low. All the counties in central Oregon are highly vulnerable in the case of drought, winter storm, earthquake, or volcanic hazards. A high vulnerability rating means that more than 10% of the population or region's assets are likely to be affected. Increasing development in the wildland-urban interface creates high vulnerability to wildfire in interface communities in Deschutes, Jefferson, and Klamath counties. During the Awbrey Hall Fire (1990) and Skeleton Fire (1996) structures were destroyed on the fringes of the city of Bend. Significant property loss was also incurred in the B & B Complex Fire in 2003. Vulnerability to floods and windstorms is moderate (1-10% affected) in the region, while the vulnerability to landslides is low (less than 1% affected). For more information on previous occurrences of hazard events, as well as the probability of future hazard events as estimated in local risk assessments, download the full regional profile. Region 6 Report Downloads (Central Oregon): Crook, Deschutes, Jefferson, Klamath, Lake, and Wheeler counties
Return to Index Region 7, Northeast Oregon Regional Profile Overview  The region of Northeast Oregon has experienced a 5% increase in population since 1990. The population in this area has grown at less than half of the rate of other areas in the state since 1990. Seventy percent of the region's population lives in incorporated areas. Of the region's houses, 45% were built before 1960, 31% between 1960 and 1980, and 24% were built after 1980. Disasters can disrupt automobile traffic and shut down local transit systems across the region, making evacuation difficult. The average commute for workers in this region is 17 minutes each way. Seventy-two percent of the region's workers drive alone to work, 12% carpool, 7% walk or use other means, and 9% work at home. Most bridges in the area have not been seismically retrofitted, posing significant risk to the commuting population in areas at risk from earthquakes. The region has historically been dependent upon agriculture and timber as major sources of jobs and income. However, the region has lost a significant portion of the timber industry and related federal jobs due to industry slowdowns and environmental reasons. Looking towards the future, agricultural, manufacturing, educational, healthcare, governmental, tourism, seasonal recreation and retail trade sectors will continue to grow and develop. The median household income in 2000 was $32,199. This is below the national average of $41,433 and the state's average of $40,916.Regional Hazard Assessment Overview Throughout Region 7, there is high probability for the occurrence of drought, wildland-urban interface fires, floods, windstorms, and winter storms. The average recurrence interval for severe drought is between 8 and 12 years. Severe winter storms occur - on average - about every 13 years. The probability of flooding is high in Wallowa County. The probability of earthquake events in this region is moderate. The probability of other hazards, including landslide and volcanic events, is generally moderate to low. All counties in northeast Oregon are highly vulnerable to drought, earthquake, wildland-urban interface fires, floods, and winter storms. A high vulnerability rating means that more than 10% of the population or region's assets are likely to be affected by a major disaster. Increasing development in the wildland-urban interface creates high vulnerability to wildfire in Baker, Grant, and Wallowa counties. In the Sloan's Ridge Fire (1996), Wildcat Fire (1996), Horse Creek Fire (2001), and Malheur Complex/Flagtail Fire many structures were destroyed on the fringes of the communities. Vulnerability to volcano-related hazards and windstorms is moderate (1-10% affected) in the region, while the vulnerability to landslides/debris flows is low (less than 1% affected). For more information on previous occurrences of hazard events as well as the probability of future hazard events based on estimates provided in local risk assessments, download the full regional profile. Region 7 Report Downloads (Northeast Oregon): Union, Wallowa, Baker, Grant
Return to Index Region 8, Southeast Oregon Regional Profile Overview  Region 8 is the second largest of the state's regions, however it consists only of Harney and Malheur counties. The least populated region in the state, the Southeast Oregon region has experienced a 19% increase in population since 1990. This growth pattern is projected to continue at a slow to moderate rate over the next 20 years. The region's population is almost equally divided between incorporated and unincorporated areas. Forty percent of the region's houses were built before 1960, 38% between 1960 and 1980, and 22% were built after 1980. The impact of a disaster can disrupt automobile traffic across the region, making evacuation difficult. The average commute for workers in this region is 16 minutes each way. Seventy-two percent of the region's workers drive alone to work, 14% carpool, and another 6% travel in other ways, the vast majority of these walking. Eight percent work at home. Most bridges in the area have not been seismically retrofitted, creating risk to the commuting population in areas vulnerable to earthquakes. The region's economy historically has been dependent upon agriculture and timber as a major source of jobs and income. Looking towards the future, agriculture, manufacturing, healthcare, government, tourism, seasonal recreation and retail trade sectors will continue to grow, providing goods, services, and work opportunities for the region's residents. The median household income for this region was $30,599 in 2000. This is well below the national average of $41,433 and the state's average of $40,916.Regional Hazard Assessment Overview: Region 8 has a high probability of drought, wildfire, flooding, and winter storms. There is a moderate probability of windstorms, and a low probability of the occurrence of other natural hazards. Because it is a fairly dry area naturally, the impacts of drought can be even more severe in Region 8. There have been a number of long statewide droughts throughout the last century, as well as a drought during 2001. The region contains large tracts of ponderosa pine forests, primarily in the northern part of Harney County, and less extensive forests in Malheur County. In 1998 and in 2000, there were significant fires within the region. Overall, the region is moderately vulnerable to fire. Flooding is a problem for Region 8 because much of Harney County and part of Malheur County is characterized by interior drainage, which means streams originating in the mountains flow into relatively flat, closed basins below. In 1993 and 1998, the region suffered from flooding resulting from persistent rain on mountain snow pack. The vulnerability in the region ranges from moderate to high. Region 8 communities are known for cold, snowy winters; however, when these conditions turn extreme, snowstorms can shut down roads and become life threatening. The winter of 1998/1999 was one of the snowiest on record for the entire state. Southeastern Oregon experienced particularly extreme impacts. The vulnerability to winter storms in the region is moderate. High winds and even tornadoes are known to affect Region 8. However, there is a lower probability of these kinds of natural hazards than those already mentioned. In 1994, strong winds in and around Ontario blowing dust caused many car accidents. In the 1960s and 1970s there were also a number of tornadoes that touched down in Malheur County. Fortunately, the vulnerability to high winds is low. For more information on previous occurrences of hazard events, as well as the probability of future hazard events as estimated in local risk assessments, download the full regional profile. Region 8 Report Downloads (Southeast Oregon): Harney, Malheur
Return to Index |
||||||||||||||||||||||||||||||||||||||||||||||||||||||
Region 6 Profile & Hazard Assessment
Region 8 Profile & Hazard Assessment