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Employment in Oregon's Tsunami Inundation Zones
by Erik A Knoder, Guy Tauer
Published Jul-21-2014

A worst-case scenario shows that nearly 37,000 jobs along Oregon's coast lie within the boundary of a tsunami inundation zone associated with a 9.1 magnitude or greater earthquake. Tsunamis occur surprisingly often along the west coast of the United States but most are small and many have their source in distant areas. James Lander and other researchers at the University of Colorado catalogued west coast tsunamis from 1806 to 1992. They counted 115 events that were tsunamis or possible tsunamis, or an average of an event about every year and a half. Wave heights were commonly one half foot to three feet and usually little if any damage was done.

March 27, 2014 marked the 50th anniversary of the Good Friday mega thrust subduction zone earthquake centered about 75 miles east of Anchorage, AK. This magnitude 9.2 temblor resulted in a tsunami that claimed the lives of 115 people including four Oregonians. Oregon sits very close to the Cascadia Subduction Zone. Just off the Oregon Coast one titanic tectonic plate of the earth's crust moves under, or "sub ducts", the larger North American plate, centimeters per year and gradually building immense pressure that is periodically released, resulting in earthquakes, some potentially very large.

Late in 2013, the Oregon Department of Geology and Mineral Industries released updated tsunami inundation maps, based on two distant-shore Alaskan (AK), and five near-shore Cascadia Subduction Zone (CZ) earthquakes. By overlaying employment data on these new tsunami zone maps, we can analyze some of the potential employment impacts of future large earthquakes. This analysis looks at just the direct employment impacts, based on business location. There may be substantial ripple effects after such a wide-ranging catastrophic event from supply chain disruption for inputs to business production, as well as severed transportation corridors, sales or customer disruptions, and workers unable to maintain normal commutes.

Large numbers of employees in tsunami-inundation zones represent economic fragility for a community, as unemployment could increase dramatically if a tsunami injures or kills employees, or if it damages or destroys businesses. Even if a business escapes damage or physical disruption due to an extreme event, it may still experience significant customer and revenue loss if the neighborhood and other businesses around it are damaged, leading customers to shop elsewhere. Neighborhood effects are especially important for retailers who rely on foot traffic, a potentially significant issue for tourist-related retail and food services within Oregon's coastal communities. Therefore, knowing where there are large numbers of employees can help identify potential economic risks and recovery challenges.

One ongoing study that includes such ripple effects is being done by an interdisciplinary team of economists and engineers at Oregon State University. They are building a tsunami vulnerability assessment tool for Clatsop County. This model estimates the potential physical and economic damage in both the inundation zone directly hit by the tsunami, and in the rest of the county that is economically interconnected. It does this by integrating an engineering model for estimating community-scale building damage with a regional economic impact model that links the inundation zone economy with the economy of the rest of the county.

Coast-Wide Impacts of Various Tsunami Scenarios
Many factors determine tsunami wave heights including how much of the fault ruptures, how much ground upheaval or displacement occurs, the duration of the ground shaking, how high the tide is during an earthquake, among others. The AK 64 scenario is the modeled inundation zone from Alaska's Good Friday distant-shore quake of 1964. The AK Max scenario represents the largest tsunami believed to be generated if an earthquake originating from tectonic plate subduction in the Alaska region occurred. The five CZ modeled scenarios represent different wave heights generated by various magnitude near-shore Cascadia earthquakes.

If the Alaskan Good Friday quake occurred in 2012, there would have been 2,565 payroll jobs within the resulting tsunami inundation zone. These types of quakes and resulting tsunamis are considered the most survivable, due to the many hours of warning, and the lack of major impact to roads, bridges and utilities that would occur from a distant-shore event.

A near-shore quake would have higher estimated wave heights and further inland reach of destructive waters, coupled with less time to evacuate. Under these near-shore (CZ) earthquake scenarios, current tsunami maps show a range of 11,159 to 34,752 annual average employment within these five tsunami models (Graph 1).

Employment impacts, as well as the total potential for death or injury, would vary greatly throughout the year. If the next big one struck in mid-January, far fewer employees, residents and visitors would likely be on Oregon's coast than in mid-August. For example, under the worst-case model (CZXXL), payroll employment in the tsunami inundation zone varied between 32,707 in January to nearly 37,000 in August 2012.

To view an interactive map of tsunami inundation zones and their potential employment impacts on coastal cities, click here.

Graph 1
2012 annual average payroll employment within tsunami inundation zone scenarios
Impact by County, Community, and Industry
Coastal geography varies greatly in Oregon. Some communities sit atop bluffs, relatively safer and better positioned to escape an incoming wall of water. Others face the reality that there is little elevation gain between the normally placid Pacific and hundreds of yards if not miles inland. In the worst-case scenarios, all Oregon counties adjacent to the ocean would be impacted. While Lane and Douglas counties have little of their total employment in this zone (0.5% and 2.4%, respectively), coastal communities within those counties are at risk. The remaining coastal counties have between 32 percent and 47 percent of their total payroll employment within the borders of the worst-case tsunami inundation zones. Most at risk is Clatsop County, with nearly 80 percent of its 2012 annual average employment in this zone (Graph 2).

The potential impact shows the leisure and hospitality industry has more than 70 percent of its coastal county employment at risk. Wholesale trade, manufacturing, retail trade, and financial activities have more than one-half of their employment within the worst case (CZXXL) inundation zone. Overall, about one-half of the five-county (Coos, Curry, Clatsop, Lincoln and Tillamook) region's payroll employment is within the worst-case scenario inundation zone.

In addition to having the highest percent of employment, leisure and hospitality had the greatest number of jobs (9,821) within the CZXXL zone (Graph 3). Retail trade (5,247), educational and health services (4,608), and manufacturing (3,615) also had significant payroll employment at risk in the coastal county areas. In some areas, there are at-risk populations served by these industries, such as students, seniors, and those with physical mobility issues. For example, employment in K-12 schools and community colleges within the inundation zones ranged from 306 (CZSM) to 778 (CZXXL). Those employment figures are only a fraction of the total served by those facilities if such an event was to occur during school hours.

Digging deeper below county-level information shows the potential community and city impacts. Under the worst-case (CZXXL) 9.1 or greater magnitude quake and resulting tsunami, the scenario points to near total employment impact within the inundation zone. Gold Beach, Seaside, Pacific City, Yachats, Rockaway and Cannon Beach have more than 90 percent of their employment within the CZXXL inundation zones. Cities including Astoria (4,685), Seaside (3,644), Warrenton (2,523), Newport (2,200), Tillamook (1,925), Lincoln City (1,723), Cannon Beach (1,347), and Gold Beach (1,236) are among the cities with the greatest number of jobs within the broadest inundation zone areas (Graph 4).

Graph 2
Percent of 2012 payroll employment in largest modeled czxxl zone
Graph 3
Percent of coastal county 2012 industry employment in CZXLL zone
Graph 4
Perent of Oregon coastal cities' 2012 payroll employment in CZXXL zone
Planning for a Potentially Bumpy and Wet Future

Although many existing employers face considerable risk from tsunamis, new businesses often incorporate tsunami risks into their business planning. For example, Jordan Cove is a proposed liquefied natural gas (LNG) export facility and electrical power plant near Coos Bay located within a seismic hazard and tsunami inundation zone. The project's developers partnered with the Oregon Department of Geology and Mineral Industries to use geologic models to estimate a tsunami's impact with an eye to reducing the risk to employees and the public at large.

For more details and to read the study, Tsunami Inundation Zone Scenarios for Oregon, visit the Department of Geology and Mineral Industries website at  oregongeology.org.