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date: 16 July 2020

Tsunami Preparedness and Mitigation Strategies

Summary and Keywords

Tsunamis are natural hazards that have caused massive destruction and loss of life in coastal areas worldwide for centuries. Major programs promoting tsunami safety, however, date from the early 20th century and have received far greater emphasis following two major events in the opening decade of the 21st century: the Indian Ocean Tsunami of December 26, 2004, and the Great East Japan Earthquake and Tsunami of March 11, 2011. In the aftermath of these catastrophic disasters, warning systems and the technologies associated with them have expanded from a concentration in the Pacific Ocean to other regions with significant tsunami vulnerability. Preparedness and hazard mitigation programs, once the province of wealthier nations, are now being shared with developing countries. While warning systems and tsunami mapping and modeling are basic tools in promoting tsunami safety, there are a number of strategies that are essential in protecting lives and property in major tsunami events. Preparedness strategies consist of tsunami awareness and education and actions that promote response readiness. These strategies should provide an understanding of how tsunamis occur, where they occur, how to respond to warnings or natural signs that a tsunami may occur, and what locations are safe for evacuation. Hazard mitigation strategies are designed to reduce the likelihood that coastal populations will be impacted by a tsunami, typically through engineered structures or removing communities from known tsunami inundation zones. They include natural or constructed high ground for evacuation, structures for vertical evacuation (either single purpose structures specifically for tsunami evacuation or existing buildings that are resistant to tsunami forces), seawalls, breakwaters, forest barriers, and tsunami river gates. Coastal jurisdictions may also use land-use planning ordinances or coastal zoning to restrict development in areas of significant risk of tsunami inundation. The relative efficacy of these strategies and locations where they have been implemented will be addressed, as will the issues and challenges regarding their implementation.

Keywords: Tsunami, preparedness, mitigation, strategies, earthquakes, subduction, warning

Tsunami, a Japanese term for “harbor wave,” is one of the deadliest of natural hazards. The two most devastating tsunami disasters of the 21st century were the Indian Ocean Tsunami of December 26, 2004, which impacted 14 countries and claimed the lives of over 235,000 people, and the Tohoku Japan Tsunami of March 11, 2011, causing 18,000 fatalities. Both tsunamis were generated by magnitude 9 earthquakes in subduction zones near coastal areas of Indonesia and Japan respectively. In assessing the current status of strategies for tsunami preparedness and mitigation, we can make three generalizations: first, the implementation of measures to promote tsunami safety has improved the survivability of major tsunami events; second, some measures have had greater efficacy than others; and third, there are remain major disparities between nations, particularly between developed and developing nations, as well as disparities based on culture and demographic characteristics. The article explores strategies for tsunami preparedness and mitigation and provides an assessment of how and where they have been implemented, their effectiveness, and the challenges inherent in protecting populations from this dangerous hazard.

Tsunamis are a series of waves typically generated by large (magnitude 7 or greater). earthquakes that occur near or under the ocean, or by volcanic eruptions, submarine landslides, and onshore landslides in which large volumes of debris fall into bodies of water. Tsunamis vary in size depending on the amount of water displaced and range from micro-tsunamis detectable only by sensitive instruments to mega-tsunamis that can affect the coastlines of entire oceans. Very large tsunamis consist of multiple waves that arrive over a series of hours, gain heights of up to 30 meters (98 feet) or more, and inundate areas several kilometers (up to three miles) inland from coastal areas. Arrival times in coastal areas vary from a few minutes for near-shore events to several hours for distant source events. Large tsunamis are generated by very large earthquakes (magnitude greater than 8) in subduction zones where an oceanic plate is subducting beneath a continental plate. Both of the major 21st-century tsunamis were generated by magnitude 9 earthquakes in subduction zones. Several factors affect the impact of a tsunami, the size of the triggering event, its directionality, the bathymetry of the ocean floor and coastal geometry. The impact is also affected by the measures that have been taken by populations to prepare for and mitigate tsunami hazards (Bernard, n.d.; USGS, n.d.).

The devastating impacts of large tsunamis occur as water displaced by earthquakes and other phenomena approach coastal areas with great velocity. In the open ocean, tsunami waves travel at great speeds, analogous to the speed of a commercial jet. As they approach shore, the speed slows and the wave height increases. Wave arrivals are typically multiple, and with large events, may occur over many hours without energy dissipation with a periodicity of a few minutes to over an hour. Variations in offshore bathymetry and topographic features on shore can focus or disperse tsunami wave energy along the shoreline, increasing or decreasing tsunami impacts. Tsunami waves are not breaking waves, but arrive as steep, turbulent and violently foaming borers, which propagate over still water and dry land in the form of a rapid surge. “Structural damage from tsunamis can be attributed to: (1) direct hydrostatic and hydrodynamic forces from water inundation; (2) impact forces from water-borne debris; (3) fire spread by floating debris and combustible liquids; (4) scour and slope/foundation failure; and (5) wind forces induced by wave motion” (FEMA, 2012, p. 16). Based on the experience of recent tsunamis, lightly framed residential structures are particularly vulnerable to tsunami hydrodynamic forces although many mid- to high-rise engineered buildings and infrastructure have survived. (For a more detailed analysis of the performance of the built environment during large tsunamis, see FEMA, 2012.)

This article will first address significant scientific developments, particularly in the capacity to detect and analyze the generating mechanisms of tsunamis, to rapidly assess the size, geographic scope and arrival times of tsunami waves at various locations, and warn populations of a potentially dangerous tsunami. The quality of warning communication has evolved over time as well. Social science research has identified the conditions under which individuals receive and process warning messages and offered recommendations regarding message content and delivery that promote effective response actions. The section “Tsunami Preparedness Strategies” will discuss tsunami preparedness strategies, which are broadly defined as tsunami education and response readiness. Mitigation, the subject of the “Mitigation Strategies” section, includes actions designed to control or eliminate the effects of the hazard, and may involve the construction of seawalls, breakwaters, and floodgates. Natural high ground, constructed high ground, and both existing buildings deemed tsunami resistant and specialized structures offer vulnerable populations opportunities for evacuation. Forest barriers are planted along coasts to slow the advance of tsunami propagation, and land-use planning may remove populations, or at least limit occupancies of hazardous coastal areas. A general discussion will follow that provides an assessment of how these strategies have performed in recent tsunami events. The challenges of tsunami preparedness and mitigation in developing nations are addressed, and several initiatives from non-governmental organizations (NGOs) and the United Nations are the subject of the “Tsunami Planning in the Developing World: United Nations Initiatives” section.

Detection and Warning: The Contribution of Science

While scientific research has provided the basis for modern tsunami warning systems, there have been attempts to anticipate the arrival of tsunamis for as long as there have been coastal communities. Pre-scientific warning was based on the observation of natural phenomena, and whether destructive tsunami events were attributed to angry gods or other supernatural forces, there were efforts to establish an understanding that ground shaking or unusual behavior of the ocean signaled an event for which communities must respond. These observed signals became embedded in the culture and were transmitted orally from generation to generation. One source of information used to establish the existence of a 1700 tsunami affecting the Pacific Northwest of the United States was oral histories of a great coastal flood and shaking earth passed down through generations of indigenous people who occupied this region before the arrival of Europeans (Ludwin et al., 2005).

Perhaps the most significant development in the scientific understanding of tsunamis followed the 1896 Meji Sanriku Japan tsunami in which the occurrence of the tsunami was linked to the fault rupture of an earthquake as the causative event (Shuto & Fujima, 2009). The practical application of this understanding was the admonition to coastal populations, “if you encounter strong earthquake shaking, move to higher ground.” The first instrumental warning system was established for Japan’s Sanriku Coast in 1941 based on seismometer data and an empirical chart of past tsunamis. Coastal residents were warned via radio, and police were called within 20 minutes of the occurrence of a possible tsunamigenic earthquake. In 1952, the Japan Meteorological Agency extended the system to all of coastal Japan. A similar warning system was adopted by the United States for Hawaii following a destructive tsunami in 1946 and major tsunamis in 1960 (Chile) and 1964 (Alaska) stimulated further developments and expansion of the warning system to other Pacific nations (National Tsunami Warning Center).

In the area of tsunami warning, a significant expansion took place in the aftermath of the 2004 Indian Ocean Tsunami (Bernard & Titov, 2015), an event that claimed the lives of 235,000 people in 14 nations. Regional warning centers were opened in the Indian Ocean, Atlantic, Caribbean and Mediterranean as well as additional centers in the Pacific Ocean. The network of deep ocean tsunami censors was expanded to 60 stations, widely distributed in vulnerable areas of the Indian and Atlantic Oceans and the Caribbean Sea. This expansion resulted from large-scale investment by nations including the United States, Germany, and Japan, and knowledge and technology transfer from developed to developing nations with significant tsunami vulnerability. In addition to the expansion of the warning system, the United Nations Intergovernmental Commission will establish standards for warning system procedures and products to promote understanding and interoperability (Bernard, Meinig, Titov, O’Neil, & Larson, 2010). A number of new technologies, or technologies adapted to tsunami warning, have also been implemented including: cabled offshore observatories, GPS buoys, and new tsunami modeling software (Bernard & Titov, 2015). Tsunami hazard assessments and efforts to model and map tsunami inundation in the areas affected by the Indian Ocean Tsunami have also been initiated (Imamura et al., 2012; Tanioka, Latief, Sunedar, Gusman, & Koshimura, 2012).

Warning systems, while areas covered have expanded and technological sophistication has increased, continue to have gaps in coverage and communication effectiveness. Tsunami warnings may be communicated to government agencies in charge of emergency management and/or directly to coastal populations at risk. Warning times vary depending on the source of the tsunami and some tsunamis, generated by natural phenomena other than earthquakes, may occur without warning. Two recent tsunami events demonstrate the challenges in tsunami warning. On September 28, 2018, an inland earthquake of magnitude 7.5 in Palu, Indonesia, possibly in combination with an earthquake triggered underwater landslide, generated an 8 meter (26-foot) tsunami that arrived within three minutes of the earthquake (Muhari, Imamura, Arikawa, Hakim, & Afriyanto, 2018; Omira et al., 2019). On December 22, 2018, in a coastal area in the region of the Sunda Strait (Indonesia), a tsunami occurred with loss of life due to activity of the Anak Krakatau volcano (Imamura, Penmellen Boret, Suppasri, & Muhari, 2019). Warnings were not issued for either of these events. The Palu tsunami was generated by an inland strike-slip earthquake that arrived too quickly for a warning to be issued. The Sunda Strait tsunami was not due to an earthquake and the Indonesian tsunami warning system is dependent upon seismic observation.

Warning communication may be conveyed via radio, television, the internet, sirens, or other auditory signals from authorities. The communication may be in the form of a “warning” which indicates that a tsunami has been generated and that communities in specific coastal areas should expect a tsunami within a stated period of time and severity (usually expressed as tsunami wave height). In addition to warnings, advisories are issued which notify coastal residents of the possibility of strong tsunami currents and waves, and watches which notify coastal areas that may be affected by an existing tsunami to be aware of the threat and to understand that they may later receive warnings or advisories (See Figures 1a and 1b). It is not uncommon for the same coastal location to receive multiple and different messages for a single tsunami event. On November 22, 2016, for example, coastal residents of Miagi Prefecture Japan received, over a five-hour period, two advisory messages, followed by a warning that was later downgraded to an advisory (Suppasri et al., 2017). These tsunami products are also associated with general instructions as to how to respond. There are additional products such as modeling of tsunami-induced current velocities directed to specific organizations including ports and harbors and off shore oil terminals (Bernard & Titov, 2015).

Tsunami Preparedness and Mitigation Strategies

Figure 1a. Domestic tsunami messages are issued for U.S. and Canadian coastlines and the British Virgin Islands. These messages include alerts and also serve to cancel alerts, when appropriate. There are four levels of tsunami alerts: warning, advisory, watch, and information statement. Each has a distinct meaning relating to local emergency response. Recommended protective actions vary within areas under warnings and advisories.

Source: United States Department of Commerce, NOAA, National Weather Service.

Tsunami Preparedness and Mitigation Strategies

Figure 1b. Tsunami warning categories of the Japan Meteorological Agency.

Source:Japan Meteorological Agency.

In addition to the actual delivery of warning products, the effectiveness of tsunami warnings is conditioned by human behavioral response by populations warned as noted by social scientists who have studied risk communication and behavior of those warned in numerous natural disasters over the years. These studies by social scientists caution that assumptions that warning dissemination will lead to belief and action oversimplifies the cognitive and behavioral processes in which warnings are heard and acted upon. Important influences on belief and action include the source(s) of the warning, the channels through which it is communicated and characteristics of the message receiver. Research has identified several stages in the processing of a warning message including: hearing the warning; believing that the warning is credible; confirming that the threat actually exists; personalizing the warning and confirming that others have received and are acting upon it; and determining whether protective action is required, whether protective action is feasible, what protective action to take and then, acting upon it (Mileti, 1999). The factors that influence belief and action vary greatly and include many demographic (e.g., age, gender, education, economic status), geographic (experience with the hazard and hazard frequency), psychological and cultural influences. Social science research has also served to debunk an older conventional wisdom that issuing warnings will result in maladaptive responses by the public. In fact, the opposite is more prevalent, and warnings must overcome a tendency to normalize a situation in which danger may be imminent (Tierney, Lindell, & Perry, 2001).

Social and behavioral scientists have also attempted to address the conditions under which disaster preparedness and mitigation strategies are adopted or not. In the best of all possible worlds, individuals and organizations would take all necessary steps to avoid, prepare for, mitigate, and cope with environmental hazards. Those exposed to hazards would seek to accurately assess their risk, identify appropriate adjustments, and adopt strategies that would offer maximum protection at reasonable costs. But there are many social, political, economic, and cultural factors that influence whether or not preparedness and mitigation strategies are adopted, and these factors have a significant impact, both positive and negative, on the likely loss of life and damage in a tsunami or other natural disaster. One basic factor is disaster, in this case tsunami, frequency. Implementing tsunami safety measures at both the individual and organizational levels depend on the frequency and severity of tsunami disasters. In Japan and Indonesia, tsunamis have been frequent and severe in contrast to the United States where historically major tsunamis have been rare and less severe. Thus, demands on government and the private sector are greater for preparedness and mitigation where recent historical tsunami disasters become part of the collective experience of current generations. At the individual level, in regions where tsunamis are infrequent, people may be unaware of or underestimate the hazard, overestimate their ability to cope in the face of disaster, underutilize available hazard strategies, rely heavily on emergency response and governmental recovery programs, and blame others for their losses (Mileti, 1999; Tierney et al., 2001).

More recent social science research has focused on use of social media in hazard warning situations (Chatfield & Brajawidagda, 2013; Tyshchuk et al., 2012; see also Sutton, Palen, & Shlovski, 2008; White, Plotnick, Kushma, Hiltz, & Turoff, 2009), differential access of some populations to warning information (Phillips & Morrow, 2007), and analyses of evacuation behavior, particularly why those endangered by an evolving natural disaster fail to evacuate in a timely fashion despite warnings (Lindell et al., 2015; Yun & Hamada, 2015). Social media have become recognized as useful in hazard situations and are becoming integrated into emergency management strategies, including hazard warnings. Noting that social media played an important role in complementing the formal warning process in a campus lockdown situation, Tyshchuk et al. (2012, p. 825) concluded that Twitter provided a “medium for real-time emergency relevant information exchange that is ‘local’ or specific to users . . . [and] allow[s] users to self-organize in groups and exchange information with large audiences affected by the emergency event.” Chatfield and Brajawidagda (2013) describe the use of Twitter as an official complement to the Indonesian government’s tsunami warning system. Research has also focused on vulnerability defined as “the characteristics of a person or group and their situation that influence their capacity to anticipate, cope with, resist and recover from the impact of a natural hazard” (Wisner, Blaikie, & Cannon, 2003). It has long been known that disasters have greater impacts on some groups, and that among certain groups, access to and compliance with warnings is problematic. A number of socio-demographic factors may limit the capacity to receive, effectively process, and adequately comply with forecasts and warnings. These factors include age, gender, race and ethnicity, poverty, disability, language and culture (Phillips & Morrow, 2007). These vulnerabilities have been highlighted in studies that have demonstrated that in an international context older persons, women, people with disabilities, tourists, poor and ethnic minorities are less likely to hear and quickly process warnings and evacuate in a timely manner (Nishikiori et al., 2006; Tatsuki, 2013).

Tsunami Preparedness Strategies

Tsunami preparedness may be broadly conceptualized as stakeholder education and response readiness as facilitated by the various tools and strategies for achieving a preparedness posture. The stakeholders include residents of coastal communities, visitors to those communities as well as local and regional governments and NGOs which must understand the risk, translate scientific and technical information regarding tsunami risk to the public, and prepare their emergency response agencies to respond effectively and implement tsunami preparedness strategies.

Education

The most fundamental outcome of tsunami education is an understanding by individuals, families, and communities that they are located in a tsunami vulnerable area and obtaining a set of practices that will allow them to survive a significant tsunami event. Individuals and organizations vulnerable to tsunamis must actively seek to understand their risk and since the occurrence of the deadliest tsunami disasters in the 21st century, most national governments now have access to tsunami information relevant to their coastal areas. The International Tsunami Information Center based in Honolulu, Hawaii, provides information in multiple languages and has links to regional centers worldwide). Once vulnerable communities understand the dangers of tsunamis and the fundamentals of response, information must be adapted to the local community in which they reside. This is typically accomplished through programs at the national level with regional and local participation, which includes tsunami modeling and mapping of coastal areas likely to be inundated in a tsunami event. Once likely inundation zones are identified (local geological observations of sand deposits and other evidence of past tsunamis can be instructive in this regard) the most fundamental preparedness strategy is evacuation; when to evacuate and where to evacuate. Evacuation strategies must include appropriate response to tsunami warnings issued by regional centers and local governments as well as addressing situations in which rapid evacuations must be initiated in the absence of a public warning. If high ground is available, evacuation to designated areas that are at elevations above probable tsunami wave heights must be mapped accompanied by the installation of appropriate signage. In addition to tsunami evacuation route signage, areas that may be inundated should also be identified with tsunami danger signage (Figures 2a–2c; Figure 2d).

Tsunami Preparedness and Mitigation Strategies

Figure 2a–c. Tsunami signage.

Source: National Tsunami Hazard Mitigation Program (NOAA/NWS),

Tsunami Preparedness and Mitigation Strategies

Figure 2d. Tsunami signage.

Source: Clarion Safety Systems.

Response Readiness

Programs of community engagement must also be implemented. The most basic tsunami preparedness strategy is the periodic conduct of drills and exercises in which local response agencies are activated, residents receive test warnings and move along designated routes to tsunami safety areas whether these areas are natural high ground within the community, approved vertical evacuation structures, or engineered high ground. Tsunami inundation maps and scenarios providing the estimated arrival times of tsunamis originating at sources both distant and near are fundamental tools which drive exercises and drills. More recently, GPS-enabled smartphone applications have been developed that relay warnings, identify evacuation routes, provide the time remaining to move to safety, and notify the user when safe areas have been reached (Sun & Yamori, 2018). Drills may be carried out collectively by an entire neighborhood or by individuals, the latter, a strategy known as the “single-person drill,” has been successfully implemented in some of the most tsunami vulnerable areas of Japan (Sun & Yamori, 2018). The fundamental goal of tsunami education is individual and collective knowledge of vulnerability and strategies for evacuation to locations of safety (See Figure 3).

Tsunami Preparedness and Mitigation Strategies

Figure 3. Single person tsunami drill. An elder person is practicing the drill accompanied by volunteers who are encouraging her and timing her evacuation.

Photo by Katsuya Yamori, Shikoku Prefecture, Japan (2018).

Mitigation Strategies

Tsunami mitigation strategies are varied and consist of actions designed to control or eliminate the effect of the hazard, often through engineered structures that will safeguard a vulnerable population, remove them from danger by facilitating evacuation or through land-use planning. These strategies include: vertical evacuation to existing natural high ground, in tsunami-resistant structures or special purpose structures; the construction of high ground above the expected tsunami inundation height; structures designed to limit the tsunami inundation through seawalls, floodgates and other engineered structures; and, land-use planning to remove some vulnerable facilities or entire communities from areas subject to repeated tsunami inundation. Another strategy is to plant forests along the coasts as natural barriers to tsunami wave flow.

Natural High Ground

In tsunami vulnerable areas where natural high ground is available and accessible, this alternative is usually the most cost-effective mitigation option. Perhaps the most widespread general educational message associated with the tsunami hazard is that if one is in a coastal area and experiences sustained ground motion from an earthquake, move to higher ground. In specific locations where natural high ground exists and local planning includes this recommendation, a number of characteristics should be known about available high ground including: whether the elevation is sufficient for safe evacuation even in the highest probable tsunami run up; whether there is adequate open space for the number of people likely to evacuate; and, whether the area can be reached with sufficient ease to accommodate those with mobility impairments. In addition, signage to direct evacuees to safe higher ground and lighting in the event of a nighttime evacuation as well as maintenance of evacuation routes are important considerations.

Existing Structures for Vertical Evacuation

There are some areas that are vulnerable to tsunamis and no accessible high ground is available for timely evacuations. Even in communities where high ground is available, some populations (e.g., the mobility impaired, elderly, persons with disabilities) may be unable to take advantage of high-ground evacuations and must rely on existing buildings for refuge. The U.S. Federal Emergency Management Agency (FEMA) has developed a guideline for design and identification of buildings that resist tsunami loads (FEMA, 2012) and a film introducing the impacts of tsunamis on existing buildings and the characteristics of tsunami-resistant design. This guideline identifies several types of existing structures for possible use in tsunami evacuations. Parking garages, which as open structures allow water to flow through lower levels, are available for use day or night, are relatively ubiquitous in urban areas, and have interior ramps leading to higher levels as well as stairs, are potentially useful in tsunami evacuations. The drawbacks of parking garages include potential damage in large earthquakes that precede tsunamis and the lack of resources to sustain an evacuated population.

Community facilities including sports complexes, community centers, schools, museums, and other public buildings may also afford opportunities for tsunami evacuation (Figures 4a4c). Many public buildings will accommodate large numbers of people and may have food service facilities and other resources needed for evacuees. Considerations include building height, resistance to earthquake ground motion and tsunami hydrodynamic forces, access and hours of operation. Commercial buildings including hotels, restaurants, and large multi-story retail businesses may also provide opportunities for vertical evacuation subject to the same considerations as public buildings. There are other structures that may provide safe refuge from tsunamis with minimal or no retrofitting, and many people survived the Tohoku tsunami in buildings that sustained damage but were tall enough and possessed sufficient strength to endure the powerful tsunami of 2011.

Tsunami Preparedness and Mitigation Strategies

Figure 4a. Reinforced concrete parking garage. Spokane International Airport.

Source: ALSC Architects, Lydig Construction/Design/Building (2001).

Tsunami Preparedness and Mitigation Strategies

Figure 4b. Sports/recreation facility.

Source: Vertical Evacuation from Tsunamis: A Guide for Community Officials (January 2009). Uploaded by Timothy J. Walsh.

Tsunami Preparedness and Mitigation Strategies

Figure 4c. Hotel and Conference Complex.

Source: Sheraton Hotels Inc.

Specially Designed Structures for Tsunami Vertical Evacuation

There are advantages to the construction of single-purpose tsunami evacuation structures over the use of existing buildings for evacuations. These structures are specifically designed to resist tsunami loading and can be situated in strategic locations that are accessible to the intended communities and away from debris sources and other hazards. Since they are single-purpose structures, they are always ready for evacuations and may have stored resources that will be needed in an emergency and will not require alterations prior to occupancy. Nor will they have structural vulnerabilities that other multi-purpose buildings may have. These structures may be a good option for low lying coastal areas where access to high ground is limited, there are no tall structurally sound buildings that could provide safe vertical evacuation or, as in the case of Japan, have aging populations for whom rapid movement to higher ground is problematic. Figure 5 is an example of a single-purpose vertical evacuation structure.

Tsunami Preparedness and Mitigation Strategies

Figure 5. Special purpose tsunami vertical evacuation structure in Tosa-Saga Village, Shikoku Prefecture, Japan.

Photo by James Goltz (2018).

Constructed High Ground

A relatively low-cost option to the construction of single-purpose tsunami evacuation structures in locations where natural high ground is distant or unavailable is constructed high ground. Soil berms in which high ground is constructed above the anticipated tsunami inundation level is a mitigation option for coastal areas. The FEMA (2012) guideline recommends a concrete lining, particularly on the ocean-facing side, to protect the berm from the scouring action of tsunami waves and a 35 centimeter (1-foot) vertical rise to 122 centimeter (4-foot) horizontal run. Soil berms have the additional advantage of being relatively safe from damage by tsunami carried debris. Berms need not be single purpose as constructed high ground could also accommodate other purposes including recreation, parking, and other activities. Figure 6 illustrates a soil berm proposed as a tsunami refuge for students, staff, and faculty at a Long Beach, Washington elementary school. An existing example is the Millennium Hope Hills in the Tohoku region of Japan in which tsunami debris was used to construct higher ground for future tsunami evacuations.

Tsunami Preparedness and Mitigation Strategies

Figure 6. Tsunami soil berm. Rendering of a 32-foot-tall berm proposed to be built behind Long Beach (Washington) Elementary School.

Source: FEMA/ City of Long Beach Washington.

Seawalls, Breakwaters, Floodgates

Seawalls are typically curved concrete barriers of various lengths that block waves from inundating coastal areas and redirect wave energy back toward the sea (University of Alaska Fairbanks, Geophysical Institute, 2010). Japan has employed this strategy in the past and continues to rely on these structures for coastal cities and towns, particularly along the tsunami-prone Sanriku Coast (see Figure 7a). This tsunami mitigation measure is costly and has proved vulnerable to scouring and overtopping in large tsunamis. Breakwaters are offshore structures that restrict the inflow of tsunami and storm waves into a harbor by narrowing the entrance (Supparsi et al., 2013). They are essentially underwater berms topped with a concrete barrier (see Figure 7b). Terapods are sometimes used as breakwaters or supplements to breakwaters (see Figure 7c). River floodgates are designed to prevent tsunamis from propagating inland via rivers and other waterways. Ground motion sensors activate some automatically, and others must be manually opened by response agencies (see Figure 7d).

Tsunami Preparedness and Mitigation Strategies

Figure 7a. Sea wall with stairway evacuation route used to protect a coastal town against tsunami inundation in Japan.

Photo: courtesy of River Bureau, Ministry of Land, Infrastructure and Transport, Japan.

Tsunami Preparedness and Mitigation Strategies

Figure 7b. Breakwater constructed at the mouth of Kamaishi Bay to prevent tsunami inundation from the Pacific Ocean.

Source: Japan Probe.

Tsunami Preparedness and Mitigation Strategies

Figure 7c. Terapods protecting a marina in Crete, Greece.

Photo by Lusinemarg.

Tsunami Preparedness and Mitigation Strategies

Figure 7d. Tsunami river flood gate at Minami-Sanriku.

Source: Tohoku University.

Forest Barriers

Tsunami “control” forests planted between the shore and cities provide a buffer, which may help dissipate the wave energy of a tsunami as it washes ashore (Suppasri et al., 2013). These forests may also serve to filter out large debris carried inland by the tsunami. Along the Sanriku Coast of Japan, spruce trees are favored for their counter-tsunami groves, though mangroves and other species of trees have also been utilized for this purpose. Tsunami control forests are effective in slowing and filtering debris for 3–5 meter (10–16-foot) tsunamis. Coastal reefs may also be protected for their potential to decrease the devastating effects of tsunamis (University of Alaska Fairbanks, Geophysical Institute, 2010; see Figure 8).

Tsunami Preparedness and Mitigation Strategies

Figure 8. Tsunami Control Forest.

Source: S. Koshimura & N. Shuto (2015). Response to the 2011 Great East Japan Earthquake and Tsunami disaster. Philosophical Transactions of the Royal Society A, 373, 20140373.

Land-Use Planning

Coastal towns and cities exposed to significant tsunami risk may choose to use zoning ordinances to mitigate the effects of tsunamis (Eisner, 2005; Strusinska-Correia, 2017; Ubaura, 2018). Regions with a long history of tsunami disasters like the Sanriku Coast of Japan or areas where tsunami modeling and mapping have identified high levels of vulnerability may effectively move vulnerable populations and critical facilities outside tsunami inundation zones. Coastal “greenbelts” have been implemented in some areas such as Crescent City, California, and Hilo, Hawaii, which have experienced major tsunami disasters in the past (see Figure 9).

Tsunami Preparedness and Mitigation Strategies

Figure 9. Beachfront Park, Crescent City, California.

Photo by Matt Hudgins.

Discussion: What Has Been Learned About These Strategies?

While there are important success stories in tsunami preparedness and hazard mitigation globally, this hazard shares with other natural hazards the fact that major tsunami disasters are rare and thus, as a low frequency and potentially high consequence phenomenon, it occupies a low priority on most public and personal agendas. In considering tsunami preparedness and mitigation strategies, we might ask: is one set of strategies to be preferred over the other? In theory, mitigation, considered by many to be “hard countermeasures,” might be preferred over preparedness because once these measures are implemented; they require little, if any, maintenance. Preparedness, as we have defined it, requires constant renewal as education and response readiness must be updated, practiced and modified for various population segments over a potentially lengthy period between events. But mitigation is expensive and the efficacy of some forms of mitigation has been challenged in the aftermath of the Great East Japan Earthquake and Tsunami of 2011. Preparedness and response readiness, though less expensive and more personally engaging for vulnerable communities, often suffers from low participation due to many social, economic and cultural factors. Thus, multiple strategies should be pursued, as no single measure is likely to provide adequate population protection. In the remainder of this section, we will explore the efficacy of mitigation and preparedness strategies as they have been implemented in various tsunami vulnerable regions of the world.

Natural high ground and structures, either multipurpose or special purpose, are the most cost-effective and practical options for vertical evacuation and tsunami safety. Most, but not all, coastal areas will have natural high ground—mountains or hills that provide safe refuge from a tsunami. Depending on tsunami wave arrival times and the distance required to reach these areas, natural high ground will be an alternative for some, but not all vulnerable populations. Some communities where natural high ground is either unavailable or too distant for population segments to reach in time must rely on available buildings or specialized structures for tsunami evacuation. A great deal of thought and analysis have gone into the identification of tsunami resistant existing buildings and the Japanese have led the way in the design and construction of specialized structures for tsunami evacuation. Tsunami signage is a critical component to identify safe routes to existing high ground or to structures identified as safe refuge from tsunamis. And drills to reinforce knowledge of safe evacuation locations are an excellent example of how tsunami hazard mitigation and preparedness work in tandem to promote tsunami survival.

Japan, more than any other nation, has relied on mitigation to protect vulnerable communities from tsunamis. This is not to say that preparedness has been ignored, but “hard countermeasures” have been a major investment and taken the form of seawalls, breakwaters, tsunami river gates and tsunami control forests. The Pacific Coast of Japan, particularly the Sanriku area of northeast Japan has experienced numerous tsunamis over the last thousand years and mitigation measures date from the mid-20th century. These measures have not been implemented for tsunamis only but designed to also mitigate the effects of high tides and wind driven waves from typhoons. These mitigation measures proved to be only minimally effective in the 2011 Great East Japan Earthquake and Tsunami. Although in some cases, these measures both slowed the speed of the tsunami and reduced the level and extent of inundation, seawalls, breakwaters and tsunami river gates were overtopped by the tsunami and many structures were damaged or destroyed. There are 300 kilometers (187 miles) of seawalls in Miyagi, Iwate and Fukushima Prefectures and according to a post-disaster assessment by the Japanese Ministry of Land, Infrastructure, Transport and Tourism (MLITT, 2011) 90 kilometers (55miles) of seawalls were damaged or destroyed by the 2011 tsunami. The damage to the seawalls was due to scouring at the foundations and sliding or overturning due to hydrodynamic forces (Supparsi et al., 2013). Breakwaters and river gates suffered similar damage and tsunami control forests were mostly swept away by the massive force and height (>10 meters or 32 feet) of the tsunami wave fronts.

We must add here that the Tohoku tsunami was a rare mega-tsunami, which had not been experienced in Japan for over 1,000 years and that performance for smaller more frequent tsunami events for which these mitigation measures were designed would have been better. Were lives saved due to the presence of these mitigation measures? We believe that the answer is yes. Tsunami breakwaters in Ofunato and Kamaishi, though badly damaged in the 2011 tsunami, reduced the wave height by several meters and delayed wave arrival by several minutes (PARI, 2011). The coastal village of Fudai in Iwate Prefecture had constructed river floodgates to prevent tsunami wave propagation in the river after experiencing damaging tsunamis in 1896 and 1993. The 15.5 meter (50-foot) gates were overtopped by 17 meter (55.8-foot) waves during the 2011 tsunami, but only a few hundred meters (.25 miles) past the gate were inundated and no villagers lost their lives. Tsunami control forests, which are capable of controlling 3–5 meter (10–16-foot) tsunamis, provided some limited protection in Sendai and Ishinomaki. Nearly all of the pine trees in the control forest in Ishinomaki survived and reduced the destructive power of the tsunami by trapping debris before it entered the city. A tsunami control forest in Natori where the Sendai airport is located is credited with reducing the tsunami inundation depth from 10–12 meters (33–39 feet) to 4 meters (13 feet) at the airport and though the forest was destroyed, it prevented debris from flowing into Sendai and its airport (Supparsi et al., 2013).

Land-use planning while, in theory, the most effective means of tsunami hazard mitigation, is often a reactive and last-resort strategy. There are clearly some areas that are simply too hazardous for human habitation. But the virtue of implementing this strategy runs against a strong current of property rights—traditional or generational land ownership, the attractiveness and lure of ocean-front property, access for oceanic businesses such as fishing, shipping, ports, and harbors, and other rights-based claims and locational contingencies. There is evidence, however, that with the advent of tsunami hazard mapping, some jurisdictions have moved critical facilities like hospitals, schools, first-response agencies (e.g., police, fire, emergency operations centers) and other facilities outside tsunami inundation zones. Land-use planning as a reactive strategy to major tsunami loses is evident as “greenbelts” or community parks in Hilo, Hawaii, and Crescent City, California, as well as areas of Japan where coastal areas have experienced major tsunamis or where future tsunamis are likely. Constructed high ground has also been implemented along parts of the Sanriku Coast of Japan, which was hit by the Great East Japan Earthquake and Tsunami of 2011.

Preparedness and response readiness measures are more widely practiced in tsunami vulnerable regions of the world and are far less costly than major engineering countermeasures that characterize tsunami mitigation. Though preparedness programs were lacking in most tsunami-prone, developing countries prior to the major tsunami events of the 21st century, in the aftermath of these events a significant effort has been made to expand warning systems and implement tsunami education. Tsunami education takes many forms: informational brochures and pamphlets provided by government agencies and NGOs; videos and animated films; community lectures, workshops and presentations by scientists and emergency managers; mapping tools and signage; and activities designed to engage multiple audiences (see Figure 10). Clearly, the most important educational products explain the nature of tsunamis, how they pose a threat to coastal communities and what actions will best ensure survival. Mapping products, either as localized components of brochures or pamphlets or stand-alone products, are equally important as they identify whether a community or parts thereof are in a tsunami-inundation zone. These mapping products also provide information on evacuation, either route maps or the location of approved vertical evacuation structures. Workshops and community-based presentations have the advantage of allowing questions and feedback from residents and, in some cases, opportunities to participate in decisions as to how the local tsunami threat will be addressed.

Tsunami Preparedness and Mitigation Strategies

Figure 10. Tsunami education products.

Source: Tsunami.gov, National Tsunami Hazard Mitigation Program and International Tsunami Information Center.

It would, however, be misleading to leave the impression that coastal community residents are the only population vulnerable to tsunamis and in need of tsunami education. In many countries with coastal areas, ocean beaches are a strong tourist draw. One of the lessons of the 2004 Indian Ocean Tsunami was that tourists were and are an important target audience for tsunami education. Thailand, one of the 14 nations seriously impacted by the 2004 tsunami, hosted thousands of tourists mainly from Europe at its beaches on the Indian Ocean at the time of the tsunami. Over 2,000 tourists died in the tsunami, half of the total were from Sweden and Germany (Cohen, 2009; Srivichai, Supharatid, & Imamura, 2007). One way in which tsunami education would benefit tourists and beach visitors is through well-maintained signage, another critical method of tsunami education. Simple messages posted on beach signs can provide information about tsunamis and provide actions that will promote safety. In coastal areas where tourists from many countries are likely to visit, signage must be displayed in multiple languages.

We have identified response readiness as a preparedness strategy and this element of preparedness takes the form of actual practice involving residents of tsunami-prone coastal areas. The most obvious example is the tsunami evacuation drill. Such drills in which tsunami vulnerable communities actually participate in moving from their homes or places of work to tsunami evacuation sites is widely practiced. These drills may involve an entire community or be pursued on an individual basis. Since tsunami wave arrival varies from a few minutes to several hours, drills must be based on mapped inundation areas and the shortest reasonable time before first wave arrival. Thus, drills are typically conducted by local government agencies or NGOs with the support of tsunami scientists. In addition to providing residents with important information regarding evacuation routes to natural high ground or vertical evacuation structures and the time required to move to safety, drills have also been useful in developing ways to assist special needs populations such as the elderly and persons with disabilities.

Tsunami Planning in the Developing World: United Nations Initiatives

There have been expanded programs of preparedness and tsunami education though large-scale programs of tsunami hazard mitigation which continue to be beyond the budgetary means of most developing nations with tsunami vulnerability. For example, the United Nations Development Programme (UNDP), with support from Japan, is working to improve tsunami disaster preparedness in 18 countries including Bangladesh, Cambodia, Fiji, Indonesia, Malaysia, Maldives, Myanmar, Pakistan, Papua New Guinea, Philippines, Samoa, Solomon Islands, Sri Lanka, Thailand, Timor Leste, Tonga, Vanuatu, and Vietnam. The focus of this and other programs (Rafliana, 2012) is on school disaster preparedness, awareness, planning, and tsunami evacuation drills (UNDP, 2019). This emphasis on schools and students seems well suited to developing nations whose populations are typically young (see Hidayati, 2012). A U.S.-based NGO, GeoHazards International, has proposed the construction of a low-cost tsunami evacuation park in Padang, Indonesia, that would accommodate 20,000 evacuees at a cost of approximately US$2 million (GeoHazards International, 2019). Such low-cost mitigation options could reduce casualties from tsunamis in many nations for whom seawalls and other more expensive mitigation options are prohibitive. The Making Cities Resilient Campaign (MCRC), a program of the United Nations Office for Disaster Risk Reduction (UNISDR) initiated in May 2010, addresses issues of local governance and urban risk, its goal, to raise the profile of resilience and disaster risk reduction among local governments and urban communities worldwide.

Just over a year following the Indian Ocean tsunami, the United Nations General Assembly convened a World Conference on Disaster Reduction in Kobe, Japan, which produced the Hyogo Framework for Action 2005–2015: Building the Resilience of Nations and Communities to Disasters. The 10-year goal was “the substantial reduction of disaster losses, in lives and in the social, economic and environmental assets of communities and countries” (UNDRR, 2005, p. 26). The framework identified five priorities, the most relevant of which for our purposes were the last two: “to increase awareness of the importance of disaster reduction policies, thereby facilitating and promoting the implementation of those policies; and, to increase the reliability and availability of appropriate disaster-related information to the public and disaster management agencies in all regions, as set out in relevant provisions of the Johannesburg Plan of Implementation” (UNDRR, 2005, p. 26). The successor to this international challenge to promote disaster resilience was the Sendai Framework for Disaster Risk Reduction 2015–2030 with a similar goal of reducing disaster risk as well as losses (UNDRR, 2015a).

Whether these initiatives will greatly improve global resilience to tsunamis remains to be demonstrated. Although there have been improvements globally in tsunami preparedness, the overall outlook for broad-based disaster resilience, particularly for developing nations is not favorable. According to a UN report on global disaster reduction:

ten years after the adoption of the Hyogo Framework for Action (HFA), global disaster risk has not been reduced significantly. While improvements in disaster management have led to dramatic reductions in mortality in some countries, the economic losses from disasters are now reaching an average of US$250 billion to US$300 billion each year. More critically, the mortality and economic loss associated with extensive risks in low- and middle-income countries are trending up.

(UNDRR, 2015b, p. xiv)

Indeed, the two very large tsunamis of the 21st century provide a marked contrast between a developing region with limited mitigation and preparedness in place and a nation in which much had been done, gives us some indication that mitigation and preparedness make a difference.

Conclusions

Progress in reducing the loss of life and damage in major tsunamis has been incremental over the centuries but the scope of devastation caused by the Indian Ocean Tsunami of 2004 and Great East Japan Earthquake and Tsunami of 2011 have resulted in major strides in scientific understanding and expansion of tsunami-warning systems, tsunami preparedness, and hazard mitigation. Implied in this statement is the fact that disaster countermeasures for tsunami and natural hazards in general are mainly reactive and implemented only after an event has occurred and caused major losses. Nevertheless, we know that tsunamis will occur in the future so all measures regardless of their timing will promote future safety in the face of this deadly natural hazard. Prior to these 21st-century tsunami disasters, there was a major discrepancy between tsunami preparedness and mitigation in advanced nations like Japan and the United States and developing nations like Indonesia, the Philippines, and parts of South America and Southeast Asia. These nations lacked warning systems as well as programs of tsunami preparedness and hazard mitigation. While this gap has not been closed, post-2004 developments in the expansion of warning systems and implementation of preparedness measures have begun to narrow the gap.Although tsunami preparedness and mitigation should be ongoing priorities on the public policy agenda of any coastal area subject to tsunamis, the immediate post-disaster environment presents an important opportunity to initiate preparedness programs and implement hazard mitigation. Disasters have the unique character of exposing vulnerabilities even in the most comprehensive programs of disaster countermeasures. Japan, which has done more in terms of tsunami mitigation and preparedness than any other nation, lost 18,000 people in the Great East Japan (Tohoku) Earthquake and Tsunami of 2011. The recovery period and rebuilding process during which major decisions must be made regarding recovery and rebuilding presents an opportunity to “build back better.” Historically, regions hit by disasters face pressures to restore communities as quickly and as economically as possible, often disregarding the need to address serious pre-disaster vulnerabilities in terms of disaster awareness and the built environment. But shortsighted measures only reproduce the conditions for future catastrophes. Recovery decisions must include programs and measures that reduce future vulnerabilities based on lessons learned from local as well as global experiences with tsunami hazards. In closing, we have demonstrated that tsunamis are a major threat to coastal communities requiring state-of-the-technology warning systems and the implementation of multiple preparedness and mitigation strategies. Multiple effective measures are needed, though the massive loss of life and extensive destruction of 21st-century tsunamis indicate that even the best countermeasures will reduce loss of life and damage, but will not eliminate either. The significant gap between developed and developing nations in regard to tsunami safety has been recognized and is being addressed, though a great deal more is needed and clearly, better tsunami-prepared developed countries must continue to share knowledge and technology with tsunami-vulnerable developing nations. In pursuing tsunami preparedness and hazard reduction, special care for vulnerable populations must be a central part of preparedness and mitigation strategies. The elderly and persons with disabilities are particularly vulnerable, and provisions for their safety must continue to be a priority for disaster planners. The tsunami disasters experienced this century have stimulated new initiatives and programs that must be sustained if we are to achieve major strides in tsunami loss reduction and long-term resilience to this major natural hazard.

Further Reading

Bernard, E. N. (n.d.). The Tsunami Story.Find this resource:

Bernard, E. N., Meinig, C., Titov, V. V., O’Neil, K., & Larson, R. (2010). Tsunami resilient communities. In J. Hall, D. E. Harrison, & D. Stammer (Eds.), Proceedings of the OceanObs’09, sustained ocean observations for society conference (Vol. 1, September 21–25, 2009). Venice, Italy: ESA Publication WPP-306.Find this resource:

Bernard, E. N., Mofjeld, H. O., Titov, V., Synolakis, C. E., & González, F. I. (2006). Tsunami: Scientific frontiers, mitigation, forecasting and policy implications. Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, 364(1845).Find this resource:

Bernard, E. N., & Robinson, A. R. (Eds.). (2009). Tsunamis (Vol. 15). Cambridge, MA: Harvard University Press.Find this resource:

Bernard, E. N., & Titov, V. (2015). Evolution of tsunami warning systems and products. Philosophical Transactions of the Royal Society A, 373(2053).Find this resource:

CGS (California Geological Survey). (2012). Tsunamis, Note 55 [Brochure]. Department of Conservation, State of California, Sacramento.Find this resource:

Cohen, E. (2009). Death in paradise: Tourist fatalities in the tsunami disaster in Thailand. Current Issues in Tourism, 12(2), 183–199.Find this resource:

Ehrlich, G. (2013). Facing the wave: A journey in the wake of the tsunami. New York, NY: Pantheon Books.Find this resource:

FEMA (Federal Emergency Management Agency). (2012, March 23). Tsunami vertical evacuation FEMA P646 [Video File].Find this resource:

FEMA (Federal Emergency Management Agency). (2012). Guidelines for the design of structures for vertical evacuation from tsunamis (2nd ed.). Washington, DC: FEMA P-646.Find this resource:

GeoHazards International (2019). Designing a tsunami evacuation park for Padang.Find this resource:

Geophysical Institute, University of Alaska, Fairbanks (2006–2010). Visual Aids, Structural Countermeasures.Find this resource:

Goltz, J. D. (2017). Tsunami Tendenko: A sociological critique. Natural Hazards Review, 18(4), 04017011.Find this resource:

Hasegawa, R. (2013). Disaster evacuation from Japan’s 2011 tsunami disaster and the Fukushima nuclear accident (Studies No. 05/13-IDDRI). Paris: Institute for Sustainable Development and International Relations (IDDRI).Find this resource:

Hidayai, D. (2012). Striving to reduce disaster risk: Vulnerable communities with low levels of preparedness in Indonesia. Journal of Disaster Research, 7(1).Find this resource:

Humboldt Earthquake Education Center. (2016). Living on shaky ground [Pamphlet]. Humboldt State University, Arcata, California.Find this resource:

Imamura, F., Muhari, A., Mas, E., Pradono, M. H., Post, J., & Sugimoto, M. (2012). Tsunami disaster mitigation by integrating comprehensive countermeasures in Padang, Indonesia. Journal of Disaster Research, 7(1), 48–64.Find this resource:

Intergovernmental Oceanographic Commission of UNESCO, NOAA International Tsunami Information Center (2014). The Great Waves [Brochure]. United Nations Educational, Scientific and Cultural Organization.Find this resource:

International Tsunami Information Center, UNESCO/IOC-NOAA Partnership (2019). Retrieved from http://itic.ioc-unesco.org/index.php.

Japan Meteorological Agency, Tsunami Warnings and Advisories, Ministry of Land, Infrastructure, Transport and Tourism, Government of Japan (n.d.). Retrieved from https://www.jma.go.jp/en/tsunami/.

Koshimura, S., & Shuto, N. (2015). Response to the 2011 Great East Japan Earthquake and Tsunami disaster. Philosophical Transactions of the Royal Society A, 373(2053).Find this resource:

Ludwin, R. S, Dennis, R., Carver, D., McMillan, A. D., Losey, R., Clague, J., . . ., James, K. (2005). Dating the 1700 Cascadia earthquake: Great coastal earthquakes in native stories. Seismological Research Letters, 76(2), 140–148.Find this resource:

Mileti, D. S. (1999). Disasters by design: A reassessment of natural hazards in the United States. Washington, DC: Joseph Henry.Find this resource:

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NOAA (National Oceanic and Atmospheric Administration). (n.d.). Tsunami Safety for You and Your Family [Brochure]. Washington, DC: NOAA, Department of Commerce.Find this resource:

NOAA (National Oceanic and Atmospheric Administration). (2018). Tsunamis[https://www.usgs.gov/faqs/what-are-tsunamis?qt-news_science_products=0#qt-news_science_products].Find this resource:

NOAA (National Oceanic and Atmospheric Administration), Pacific Marine Environmental Laboratory, NOAA Center for Tsunami Research. (n.d.). Retrieved from http://nctr.pmel.noaa.gov/indo_1204.html.

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Pacific Tsunami Museum, Hilo Hawaii (1996–2014). Retrieved from http://www.tsunami.org.

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Raby, A., Macabuag, J., Pomonis, A., Wilkenson, S., & Rossetto, T. (2015). Implications of the 2011 Great East Japan Tsunami on sea defense design. International Journal of Disaster Risk Reduction, 14, 332–346.Find this resource:

Rafliana, I. (2012). Disaster education in Indonesia: Learning how it works from 6 years of experience after the Indian Ocean Tsunami in 2004. Journal of Disaster Research, 7(1).Find this resource:

San Diego County Office of Emergency Services. (2009, February 5). Tsunamis: Know what to do! (Children’s video) [YouTube Video].Find this resource:

Shuto, N. (2019). Tsunami hazard mitigation. Proceedings of the Japan Academy Series, 95(4), 151–164.Find this resource:

Shuto, N., & Fujima, K. (2009). A short history of tsunami research and countermeasures in Japan. Proceedings of the Japan Academy Series B, 85.Find this resource:

Srivichai, M., Supharatid, S., & Imamura, F. (2007). Recovery process in Thailand after the 2004 Indian Ocean tsunami. Journal of Natural Disaster Science, 29(1), 3–12.Find this resource:

Sun, Y., & Yamori, K. (2018). Risk management and technology: Case studies of tsunami evacuation drills in Japan. Sustainability, 10(9), 2982.Find this resource:

Suppasri, A., Shuto, N., Imamura, F., Koshimura, S., Mas, E., & Cevdet Yalciner, A. (2013). Lessons learned from the 2011 Great East Japan Tsunami: Performance of tsunami countermeasures, coastal buildings, and tsunami evacuation in Japan. Pure and Applied Geophysics, 170(6–8), 993–1018.Find this resource:

Synolakis, C. E., & Bernard, E. N. (2006). Tsunami science before and beyond Boxing Day. 2004. Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, 364(1845), 2231–2265.Find this resource:

Tanioka, Y., Latief, H., Sunedar, H., Gusman, A. R., & Koshimura, S. (2012). Tsunami hazard mitigation at Palabuhanratu, Indonesia. Journal of Disaster Research, 7(1), 19–25.Find this resource:

Tierney, K. J., Lindell, M. K., & Perry, R. W. (2001). Facing the unexpected: Disaster preparedness and response in the United States. Washington DC: Joseph Henry Press.Find this resource:

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UNDRR (United Nations Office for Disaster Risk Reduction). (2005). Hyogo Framework for Action 2005–2015: Building the resilience of nations and communities to disasters (Report of the World Conference on Disaster Reduction, January 18 to 22, 2005). Kobe, Hyogo, Japan.Find this resource:

UNDRR (United Nations Office for Disaster Risk Reduction). (2015a). Sendai Framework for Disaster Risk Reduction 2015–2030. United Nations.Find this resource:

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United States Department of Homeland Security (n.d.). Retrieved from https://www.ready.gov/tsunamis.

United States Department of Commerce, NOAA, National Weather Service, US Tsunami Warning System (2019). Retrieved from https://www.tsunami.gov/.

Washington State Emergency Management Division (n.d.). Tsunami Information and Preparedness [Brochure]. State of Washington.Find this resource:

Yamori, K. (2014). Revisiting the concept of tsunami tendenko: Tsunami evacuation behavior in the Great East Japan Earthquake. In H. Kawase (Ed.), Studies on the 2011 off the pacific coast of Tohoku earthquake. Tokyo, Japan: Springer.Find this resource:

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