Cascadia Earthquake: Part 4 Land, Sea and Air


The next one hundred pages will be in article form.  I will draw out the important parts, and may comment of a few.

Click here for the Oregon Resilience Plan

The page numbers are the electric (vs. print out) number and not the true page numbers.


  •  Our knowledge of the locations of faults and the geological history of major events in Oregon is      very recent. Although Oregon has low seismicity in comparison to California and Washington, there is potential for less frequent—but much larger and more damaging—earthquakes than the crustal earthquakes that have occurred regularly in those states. Oregon has not yet seen the effect of a large damaging earthquake, and ODOT has so far expended minimal resources on  seismic retrofitting. As a result, much of Oregon’s highway system will not be usable immediately after a major seismic event. Pg 125

Great photos of bridge damage on pages 127 through 130

The World has Not Seen

“Oregon, or even the entire nation, has never witnessed a disaster of this magnitude in modern history; therefore, we can only speculate about how this event will impact Oregonians.

 “There will not be enough firefighters to assist every household or business, nor enough medical staff to help every injured person, nor enough police officers to go door to door reminding people to be calm and quickly move to higher ground to avoid the oncoming tsunami.” Page 130

Coastal Area Impacts

 “Coastal residents have been advised to get away from the shore on foot, but tourists and commercial travelers are not likely to know that.” Pg 131

For most of Oregon’s coastal cities, U.S. 101 serves as the main route to other destinations. Unfortunately, after a Cascadia subduction zone earthquake, most of this route will be impassable. Most bridges carrying U.S. 101 were not designed for seismic loading and will suffer major damage under the expected ground shaking. Many other bridges, if they survive the shaking itself, will be washed away by the tsunami. In addition to the bridge damage, many highway segments are expected to become heavily damaged and impassible due to landslides. The latest assessment of state-owned bridges in Oregon shows that of 135 total bridges carrying U.S. 101, 56 bridges are expected to collapse, and 42 bridges will be heavily damaged. Some of these bridges are signature bridges and registered as historic.  Pg 131

J;  I hope you have a good pair of walking shoes.  PAGE 132 VERY IMPORTANT CHART!!!

“Because of the terrain these highways were built on, many of them lack options for detouring traffic around a bridge that collapses. The situation can become even more critical if the earthquake strikes during winter, when many of the state’s secondary routes experience seasonal closure.” Pg 132

Interstate 5 and Mid-Willamette Valley Impacts

“From a total of 348 bridges carrying both northbound and Transportation southbound traffic, five bridges are expected to collapse and 19 bridges to be heavily damaged during the Cascadia subduction zone event.”  Pg 133

Coastal Area: Impacts from Landslides and Rockfalls

“Currently, 526 known unstable slopes directly affect U.S. 101. Many of these slides will fail catastrophically during the primary earthquake, while many others will fail during or soon after the tsunami. Slopes that do not immediately fail during the primary seismic event will be destabilized to varying degrees and may fail soon after, either during strong aftershocks or else at some time during the rescue and recovery efforts.” Pg 141

Interstate 5 and Mid-Willamette Valley: Impacts from Landslides and Rockfalls

  •  In all, there are 49 known landslide and rockfall areas along I-5. Other unstable areas are suspected. In the event of a Cascadia subduction zone earthquake, therefore, the most important route in the state will not be without problems. Many of the slides through the Willamette Valley are minor and can be readily mitigated. Most of the slides in the Portland area have been treated, but some could result in lengthy repairs and service disruption. For the Portland area, adequate detours exist in areas that are not as vulnerable to landslides, but delays will occur. The greatest       concern for this route is the mountainous areas of southern Oregon. Unfavorable geology—in terms of geologic structure, materials, and groundwater—has formed some very large, complex landslides in this area. These slides have the capacity to cut this route off on the southern end for many weeks while repairs take place or detours are constructed. Pg 142


Page 143 is a good snapshot of bridges, highways, and tunnels

Air Transportation

“The state of Oregon has an extensive aviation system that provides valuable transportation options for the public, ranging from small airports in remote regions of the state to large commercial service airports. Ninety-seven public-use airports provide support to the economic health and vitality of Oregon and contribute to the quality of life for its citizens and visitors.”

• Fifty-seven public-use airports are partially supported by FAA and included in the National Plan of Integrated Airport System (NPIAS).

• Sixteen public-use airports are either owned by other municipalities or are privately owned.

• Over 400 private airports and landing strips are located within Oregon.

Page 145

“During the emergency response, for example, displaced residents, injured people, and the elderly may need to be evacuated by means of airports; and airports will also provide a staging area for needed supplies (such as water, food, medical supplies, and materials for temporary housing). Until highway and rail transportation can be fully restored, air transportation, along with ships off the coast, will be the lifelines for Oregon’s citizens.” Pg 146


Page 148 is a map of the airports.

 Columbia and Willamette Navigation Channels

“A Cascadian event could significantly impact the river system and shipping channels. The jetty at the month of the Columbia is susceptible to severe damage from significant seismic event and tsunami. Failure of the jetties would significantly impact the channel. The channel depth at the mouth would likely be severely constrained due to sands migrating in from the beaches adjacent to the jetties. Additionally, the navigability of the Columbia River Bar would be difficult and unsafe for many vessels.” Pg 148

In addition, the pile dike systems along the river, which are intended to prevent sediments

  •  From migrating into the channel, are susceptible to failure during a major seismic event. Significant failures could dramatically impact the hydrology of the Columbia River. Depending on the seismic impact, deep-draft ships that are in transit in the waterway could become stuck due to a sudden shifting of material: This shift would cause the navigation channel to become shallower, cutting off navigation by other vessels and endangering the ships themselves. Additionally, structures that collapse into the navigation channel would need to be removed to allow ships to pass safely. Initially, shallow-draft barges may be the only viable option to move material and goods to and from marine terminals; or ship calls will be diverted to other,      unaffected ports and regions. Marine terminals near the coast will also be exposed to the effects of tsunami waves, which could severely impact dock structures and support facilities. Timely restoration of the channel to resume current shipping operations is dependent upon the availability of dredges and federal funding authorizations. Pg 149

Page 150 is the map of docks in Oregon/Washington

“In other words, the elevation of the shoreline is expected to drop during the earthquake and just before the first tsunami waves arrive.”    Pg 151


“Waterborne rescue and recovery operations may have to be provided through coastal ports; this may be the only viable option for many of Oregon’s coastal communities if highway corridors fail. So even though the infrastructure of many coastal ports may be devastated, their very locations will have to serve as landing sites for waterborne support (from barge, amphibious, and shipping operations). Temporary facilities provided by barges and cranes may be used to restore makeshift docks quickly for rescue and recovery operations, as was experienced in Haiti. Functionality for commerce would take longer.”  Pg 152

Public Transit Services

“Transit providers are generally located on Oregon’s lifeline routes. While this means that transit agencies are well placed to be able to assist with response and recovery activities, it also means that the transit system is dependent on local roads and highways and cannot respond if roads are impassable. Once roadways are cleared for minimum critical vehicle travel, public transit vehicles may be deployed by emergency command for the purposes of evacuating residents and transporting relief personnel.”  Pg 155

  • The importance of the human factor in recovery activities following a major emergency is often underrated. Public transit is dependent on drivers, mechanics, dispatchers, and supervisors all working together to maintain and support daily operations. Some transit drivers are volunteers. Personnel must first be able to get to central agency locations, where both vehicle and communication assets must be operable, in order to provide public services. This also means there must be a way for these men and women to know that their families and loved ones are safe while  they return to work. Although some emergency response personnel, such as firefighters and National Guard troops, do have commercial driver’s licenses, they are generally not accustomed to driving buses, nor are they necessarily familiar with local streets and routes. Most importantly, drivers for demand-response transit services know where the vulnerable populations in their communities reside, which can be critical to saving lives in the hours and days immediately following a catastrophic event. Pg 155

That wraps up part 4.  Tomorrow will be part 5. 


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