Tsunami Preparedness and Mitigation
A tsunami is a series of ocean waves caused by earthquakes, landslides, or volcanic eruptions. These waves can kill and injure people and destroy entire communities. Tsunamis strike as fast moving walls of water that flood, drain, and re flood the land for hours. Tsunamis can flood more than a mile inland. But we can take action to prepare. Prepare now to protect yourself and your loved ones.
Tsunami warning centers and coastal communities play critical roles in protecting the public from tsunamis. All low-lying coastal areas are vulnerable to tsunamis. For this reason a tsunami early warning system may not always be effective. Tsunamis are often accompanied by natural signs that can be sensed by an alert person. Recognizing any of these tsunami warning signs at the beach or coast could save your life.
Effective early warning systems will save lives. To be effective, there must be synergy among all levels of the warning system, with international, national, and community actions harmonized to effect a seamless warning and response chain —an end-to-end warning system from detection to safe evacuation. Warnings are most effective when there is continuous public awareness and preparedness to support appropriate public action.
Many of the things you need to do to prepare for a tsunami are the same as you would do to prepare for other hazards that may affect your community. It is not hard, and it is not expensive.
Understand Tsunami Warnings
Understand the two types of tsunami warnings, official and natural, and how to respond to them. They are equally important, and you may not get both. Respond immediately to whichever you receive first.
Official Warnings
An official tsunami warning will be broadcasted through local radio and television, marine radio, wireless emergency alerts. It may also come through outdoor sirens, local officials, text message alerts, and telephone notifications. Evacuation is recommended.
Move to a safe place on high ground or inland (away from the water). Follow instructions from local officials. In the case of a local tsunami, there may not be time to wait for an official tsunami warning.
Natural Warnings
A natural tsunami warning may the first, best, or only warning that a tsunami is on its way. Natural tsunami warnings include strong or long earthquakes, a loud roar (like a train or an airplane) from the ocean, and unusual ocean behavior.
The ocean could look like a fast-rising flood or a wall of water. Or, it could drain away suddenly, showing the ocean floor, reefs, and fish like a very low, low tide. Any of these warnings, even just one, means a tsunami could arrive within minutes.
Protect yourself from the earthquake, if necessary, and move quickly to a safe place on high ground or inland (away from the water). Do not wait for an official warning.
The elements of an effective warning system can be summarized as follows:
Proper instruments that enable the early detection and assessment of threat of potentially harmful earthquakes and tsunamis. The data obtained by these instruments must be readily available to all nations continuously and in real-time.
The National Warning Centre must be able to analyze and forecast the impact of tsunamis on coasts in advance of the waves’ arrival, and the local, regional, and/or national Civil Protection or Disaster Management Agencies must be able to immediately disseminate the alerts and enable evacuation of all vulnerable communities. The communications methods must be reliable, robust, and redundant, and work closely with the mass media and telecommunications providers to accomplish this broadcast as well as integrate social media. Vulnerable populations must be informed in an understandable and culturally appropriate way.
Awareness that educates and informs a wide populace on how to recognize a tsunami natural warning signs and what to do, from ordinary citizens to lifeline and critical infrastructure services. The public must know a tsunami’s natural warning signs and where to evacuate immediately because a local tsunami may hit within minutes and before an official tsunami warning can be issued and received. Respect for and use of indigenous knowledge is important.
Preparedness arrangements that practice procedures and actions necessary to save lives and reduce impact. Drills and exercises, and proactive outreach and awareness are essential for reducing tsunami impact. The inclusion of natural hazards science and disaster preparedness subjects in the school curriculum will prepare and carry awareness to the next generations. Gender-related issues in preparedness and family responses in emergencies need to be accommodated.
Response planning that identifies and creates the public safety procedures and products that enable fast action. This includes both land evacuations of people and marine evacuations in ports, harbours, and protection of airports and critical and lifeline facilities. It is necessary to create and widely disseminate tsunami evacuation maps that include instructions on when to go, where to go, and how to go. Evacuation zones, shelters, and evacuation routes need to be clearly identified, and widely known by all segments of the coastal and marine population.
Tsunami-resistant engineering and building codes, and prudent land-use policies that are implemented as pre-disaster mitigation. Tall, reinforced concrete buildings, or natural berms, can offer safe places to which people can vertically evacuate if there is no time to reach higher ground. Long-term planning to avoid placing critical infrastructure and lifeline support facilities in inundation zones will reduce the time needed for services to be restored and reduce economic impact.
Stakeholder coordination to facilitate effective, seamless actions in warning and emergency response. Clear designation of the national or local authority from which the public will receive emergency information is essential to avoid public confusion, which would compromise both public trust and safety.
High-level advocacy at community, national, and international levels that ensures a sustained commitment to prepare for what are infrequent, but high-fatality natural disasters such as tsunami.
Plan for Evacuation
Tsunami evacuation planners must consider the different responses for a local, regional and distant source event. A distant source tsunami allows for more than three hours for evacuation. A regional tsunami is particularly challenging, as only one to three hours exist to decide and conduct an evacuation. A local tsunami (less than one hour between tsunami trigger and wave arrival) will require immediate self-evacuation based on ground shaking or other natural warning signs observed by community members. Local tsunamis and earthquakes should be planned for together, as earthquake impact may make evacuation challenging. The time required to execute an evacuation should be analyzed and built into the decision-making procedure. Tsunami evacuation plans, maps, and procedures should be developed with community and government input so that evacuation advice (or orders) to evacuate are clear and the evacuations themselves orderly.
Tsunami evacuation maps are a critical product of the tsunami evacuation planning process. Evacuation maps, based on the expected inundation maps, must delineate zones that need to be evacuated when a dangerous tsunami is imminent. The evacuation zones are typically indicated using contrasting colours. Multiple evacuation zones (and colours) can be used, depending on the hazard assessment for instance where there is significant difference between a local or distant tsunami, or an extreme tsunami threat). In high density locations, the maps should indicate the optimum evacuation routes to safe areas. As not all areas will have access to natural high ground, some locations may need to consider adopting a policy of vertical evacuation to a designated (and sign posted) strong building, or for sheltering in place. Ideally, the public should evacuate by foot when possible to avoid creating traffic congestion. Evacuation plans and maps should be vetted at community meetings and corresponding authorities, and an educational tsunami evacuation brochure developed for wide distribution.
Evacuation planning is the process for identifying areas potentially at risk from tsunamis, and the actions required to ensure the safety of people while evacuating from those areas. It is fundamental that evacuation plans are integrated with the tsunami early warning system, as well as with other public and private sector emergency plans. Evacuation plan components should cover types of evacuation (e.g. voluntary, mandatory) and the management of the respective phases (e.g. decision, notification, process, and shelter, return).
Special planning considerations must be given to the portion of affected communities that are incapable of or will have difficulty evacuating without assistance, such as hospitals. In addition, tsunami response plans, including shutdown of services and evacuation of personnel, should be in place for critical facilities and infrastructure.
Evacuation procedures should include guidance to emergency services at the local level; thereby, ensuring evacuation zones are closed off and secured until the tsunami warning is cancelled and the threat of a tsunami no longer exists. Once areas have been evacuated, roadblocks, barricades, and/or a system of patrols should be set in place to keep the public from returning to evacuation zones and to keep people with malicious intent out. The decision to allow re-entry (e.g. all-clear) will be made by Emergency Management officials.
Signage is an effective mechanism for public education on the risk posed by tsunamis and the appropriate evacuation response to a tsunami event. Stakeholders, including the public, should examine signage locations and types during the planning process. Four basic categories of tsunami sign types are: evacuation zone, evacuation route, evacuation safe-location/assembly areas and information board. Many different tsunami signs are available around the world, though three basic signs (hazard/evacuation zone, horizontal safe point, and vertical shelter) were agreed upon and adopted by the International Organization for Standardization. Signage must be in sync with local community education, preparedness, and mitigation programs.
Exercising these plans and procedures helps to validate, increase and sustain awareness and preparedness. Tsunami exercises can range from orientation workshops and straightforward communications tests to full-scale alerting and evacuations of people from tsunami hazard zones. A perfectly executed warning will be useless if people, agencies and organizations do not know how to respond to the warning. Exercise also support the planning process through review and assessment.
Plan to evacuate on foot if you can; roads may be impassable due to damage, closures, or traffic jams.
It is also important to know what to do during and after a tsunami. This includes staying informed and staying safe. After a tsunami, local officials will assess the damage and decide when it is safe to return. Even though the danger of the tsunami has passed, other dangers may remain (debris, fires, unstable structures, etc.). If there is a lot of damage, it may be days before it is safe to return to affected areas.
Community preparedness is vitally important because it enables a rapid appropriate response to both official warnings and the natural signs of a possible tsunami. This is critical for saving lives for all tsunami events, and it is even more essential for locally generated tsunamis. Without tsunami community preparedness, the chances of people to escape and survive a locally generated tsunami are minimal. Two important components of community preparedness are science-based tsunami inundation maps and participatory-developed tsunami evacuation plans and maps. Only when you are well aware of the tsunami hazard, your community can be prepared against this natural threat. This guide describes how to develop tsunami inundation and evacuation maps and how to increase the community tsunami readiness and preparedness, including through drills and exercises.