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Tsunami

NEW! MANUAL FOR TSUNAMI VERTICAL EVACUATION STRUCTURES: Coastal communities that lack sufficient natural or artificial high ground are particularly vulnerable. Residents, employees, and visitors will have limited time to evacuate to safety. For at-risk communities, tsunami vertical evacuation structures are a way to save lives. Evacuation structures are designed to withstand an earthquake, aftershocks, liquefaction, and multiple tsunami waves. Communities on Washington State’s Pacific Ocean coastline have limited resources. Tsunami vertical evacuation structures are complex and relatively new. Building these high-performance structures requires a variety of partners and expertise. Communities also have to administer a robust public engagement process to build support, plan, and determine funding options. Given all these factors, Washington State Emergency Management Division felt that it was important to provide coastal communities with a manual that could help them navigate this process and protect their communities.

Chapter 1 contains the core of this report and describes the 7-phase process. This process lays out the various steps that communities should follow to plan, design and construct tsunami vertical evacuation structures.


What's a tsunami?

The Pacific Coast, Strait of Juan de Fuca, Puget Sound, and large lakes are at risk from tsunamis, which are trains of waves that threaten people and property along shorelines. Sudden raising or lowering of the earth’s crust during earthquakes generally causes a tsunami, although landslides and underwater volcanic eruptions also can generate them. Movements of the sea floor or lake bed, or rock fall into an enclosed body of water, displace the water column, setting off a series of waves that radiate outward like pond ripples.

Only as a tsunami approaches land does it become a hazard; in shallow water, it gains height as its waves slow and compress. Tsunamis do not resemble their usual icon, a towering wave with a breaking crest. Instead, they come onshore resembling a series of quickly rising tides, and they withdraw with currents much like those of a river. Swift currents commonly cause most of the damage from tsunamis. A Pacific Ocean tsunami can affect the entire Pacific basin, while a tsunami in inland waters can affect many miles of shoreline.

Tsunamis typically cause the most severe damage and casualties near their source. There, waves are highest because they have not yet lost much energy. The nearby coastal population often has little time to react before the tsunami arrives. Persons caught in the path of a tsunami often have little chance to survive; debris may crush them, or they may drown. Children and the elderly are particularly at risk, as they have less mobility, strength, and endurance.

Instant Tips

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If you live on the coast, you might be curious about the Tsunami All-Hazard Alert Broadcast (AHAB) and its pole-mounted siren system deployed throughout the coast. During a routine TEST of the system, which is conducted on the first Monday of every month at noon, the sirens will play the Westminster Chimes (click here to listen to what it sounds like). Upon the issuance of a TSUNAMI WARNING, the siren will play a wail sound (click here to listen to what it sounds like) and a voice message will follow the siren.

  • Tsunami Warning: Take Action—Danger! A tsunami that may cause widespread flooding is expected or occurring. Dangerous coastal flooding and powerful currents are possible and may continue for several hours or days after initial arrival. Follow instructions from local officials. Evacuation is recommended. Move to high ground or inland (away from the water).
  • Tsunami Advisory: Take Action—A tsunami with potential for strong currents or waves dangerous to those in or very near the water is expected or occurring. There may be flooding of beach and harbor areas. Stay out of the water and away from beaches and waterways. Follow instructions from local officials.
  • Tsunami Watch: Be Aware—A distant earthquake has occurred. A tsunami is possible. Stay tuned for more information. Be prepared to take action if necessary.
  • Tsunami Information Statement: Relax—An earthquake has occurred, but there is no threat or it was very far away and the threat has not been determined. In most cases, there is no threat of a destructive tsunami.

Note: Tsunami warnings, advisories and watches may be updated or cancelled as information becomes available. Advisories, watches and information statements may be upgraded if the threat is determined to be greater than originally thought.

Tsunami warnings are broadcast through local radio and television, marine radio, wireless emergency alerts, NOAA Weather Radio and NOAA websites (like Tsunami.gov). They may also come through outdoor sirens, local officials, text message alerts and telephone notifications. Learn how to get tsunami warnings here.

There may not always be enough time for an official warning, so it is important that you understand natural warnings. If you are at the coast and feel a strong or long earthquake, see a sudden rise or fall of the ocean or hear a loud roar from the ocean, a tsunami may follow. This is your warning. Take action and move to a safe place. Do not wait for official instructions.

Tsunami Evacuation and Inundation Maps

Partnering with local communities, Washington’s Emergency Management Division and Department of Natural Resources helps develop evacuation maps based on known inundation zones. These maps along with additional area specific information can be found by following this link.

Tsunami Warnings and Information

Tsunami Education Materials

Project Safe Haven Reports

Project Safe Haven is a grassroots, community driven, public process currently taking place on the Washington Coast to identify areas for future vertical evacuation structures. Partnering with local residents, its mission is to develop a community responsive vertical evacuation strategy along the Washington coast.

Final Report Cost Breakdown

2016 Final Report

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