In my previous blog post, I explored how disaster risk reduction strategies such as early warning systems, tsunami awareness, and education and outreach activities have helped reduce fatalities during tsunami events. However, the case studies reviewed during my summer 2025 research with the Disaster Lab show that, much like a sieve or colander, these protective measures may not always perform effectively. This post turns to the gaps that remain, examining how limitations in detection technologies and urban infrastructure can delay evacuation and increase risk before a tsunami arrives.

Limitations of Early Warning Systems

While early warning systems are an essential component of tsunami risk reduction, the literature shows that these systems are not effective across all tsunami types. Most tsunami detection technologies are primarily designed to identify tsunamis generated by large submarine earthquakes, rather than those caused by volcanic eruptions or submarine landslides. As a result, non-seismic induced tsunamis (notably those caused by volcanic eruptions or submarine and aerial landslides) are often detected later, increasing the likelihood of delayed evacuation and higher fatality risk.

This limitation was evident during the 2018 Sunda Strait tsunami in Indonesia. The tsunami was generated by a volcanic flank collapse rather than an earthquake, meaning residents received little to no advance warning [1]. Existing ocean buoys are designed to detect tsunamis caused by earthquakes exceeding approximately magnitude 6.5 with shallow hypocentres, conditions that were not present during this event [2]. Additionally, buoy-based systems typically require several minutes to register abnormal sea level changes, which is insufficient for landslide induced tsunamis that can reach shorelines within minutes of generation [1].

Similar detection challenges were observed following the Hunga Tonga–Hunga Haʻapai volcanic eruption. In Aotearoa New Zealand, tsunami advisories were issued only about one hour prior to wave arrival, as monitoring systems began detecting tsunami signals several hours after the eruption [3]. Although this provided some time for response, the delay highlights how existing early warning infrastructure is less effective for volcanic tsunamis than for earthquake generated events.

Urban Planning and Evacuation Challenges

Beyond detection and warning systems, tsunami risk is also shaped by the physical layout of cities and towns. Urban features that slow evacuation, including road congestion and limited transport capacity, are strongly associated with higher fatality risk during tsunami events [4].

Across multiple case studies, traffic congestion has emerged as a major challenge during tsunami evacuations, slowing movement to safe areas and increasing exposure to incoming waves [1,4]. In some contexts, evacuation has also introduced additional risks. In Kodiak, Alaska, for example, one evacuee was killed in a hit and run incident during a tsunami evacuation, highlighting how overwhelmed infrastructure can turn evacuation itself into a source of danger [5].

The 2018 Sulawesi tsunami further illustrates how evacuation challenges disproportionately affect vulnerable populations. Research notes that elderly individuals and those with limited mobility required more time to evacuate, contributing to increased risk in already hazardous conditions [4]. When evacuation routes are congested, poorly designed, or insufficiently planned, these groups face heightened exposure to injury and death.

These findings underscore the need for urban planners and disaster management practitioners to integrate tsunami risk into development planning. More specifically, researchers have called for critical facilities such as schools, hospitals, and nursing homes to be located outside high-risk coastal zones [4]. Road design and capacity must also be considered in evacuation planning, with targeted road widening and evacuation drills assisting in identifying potential bottlenecks before an event occurs.

Conclusion

These case studies demonstrate that, despite the safety nets established through disaster risk reduction strategies, important gaps remain due to technological limitations and urban constraints. Improving detection capabilities for non-seismic induced tsunamis, alongside evacuation-informed urban planning in disaster-prone regions, is therefore essential for reducing loss of life during tsunami events. These insights underscore the need for sustained investment in both technological innovation and integrated disaster and urban planning as core components of tsunami preparedness strategies.

– Abraham Alexander

References

[1] Takabatake, T., Shibayama, T., Esteban, M., Achiari, H., Nurisman, N., Gelfi, M., Tarigan, T. A., Kencana, E. R., Fauzi, M. A. R., Panalaran, S., Harnantyari, A. S., & Kyaw, T. O. (2019). Field survey and evacuation behaviour during the 2018 Sunda Strait tsunami. Coastal Engineering Journal, 61(4), 423–443. .

[2] Syamsidik, S., Benazir, B., Umar, M., Margaglio, G., & Fitrayansyah, A. (2019). Post-tsunami survey of the 28 September 2018 tsunami near Palu Bay in Central Sulawesi, Indonesia: Impacts and challenges to coastal communities. International Journal of Disaster Risk Reduction, 38, 101229. .

[3] the tsunami, with a major emphasis on risk awareness and evacuation behaviours.

Harrison, S. E., Lawson, R. V., Kaiser, L., Potter, S. H., & Johnston, D. (2025). Understanding mariners’ tsunami information needs and decision-making contexts: A post-event case study of the 2022 Tonga eruption and tsunami. IScience, 28(2), 111801. .

[4] Harnantyari, A. S., Takabatake, T., Esteban, M., Valenzuela, P., Nishida, Y., Shibayama, T., Achiari, H., Rusli, Marzuki, A. G., Marzuki, M. F. H., Aránguiz, R., & Kyaw, T. O. (2020). Tsunami awareness and evacuation behaviour during the 2018 Sulawesi Earthquake tsunami. International Journal of Disaster Risk Reduction, 43, 101389. .

[5] Venua, B. (2023, July 18). Kodiak resident dies in hit-and-run during Saturday’s tsunami evacuation. Alaska Public Media; AKPM. /. Sourced from: .

The post Before the Wave: Gaps in Tsunami Preparedness appeared first on The Disaster Lab.

During the summer of 2023, I spent my school break as a Caribbean Catastrophe Risk Facility SPC Intern at the University of the West Indies’ . Although my coursework as a geography major had introduced me to natural hazards and climate change, this internship was my first interaction with the concept and practice of disaster risk reduction (DRR).

At its core, disaster risk reduction refers to policies, and strategies aimed at preventing new disaster risk, reducing existing risk, and managing residual risk that cannot be completely avoided [1]. In practice, DRR encompasses a wide range of measures, including planned relocations, the development of proactive infrastructure such as flood defenses, and disaster education and awareness programs [2].

Two years later, I found myself engaging with this concept once again through my research at the Disaster Lab on tsunami-related research. Across the literature I reviewed, one pattern emerged: DRR strategies are instrumental in reducing fatalities during tsunami events. Drawing on the case studies examined, this article highlights how DRR strategies, particularly early warnings, tsunami awareness, and evacuation practices, influence evacuation outcomes and human impacts during tsunami events.

Early Warning Systems

are often the first opportunity for coastal populations to take protective action during a tsunami. By providing advance notice of tsunami waves, these systems allow residents to evacuate before waves arrive, reducing the risk of injury and loss of life.

This was evident through the effectiveness of timely warnings following the 2024 in Japan, a compound disaster involving earthquake damage, landslides, fires and tsunami impacts. Of the 241 recorded fatalities, only two deaths were directly attributed to the tsunami, while the majority resulted from the earthquake, landslides and other related hazards. Research suggests that the prompt dissemination of a major tsunami warnings issued shortly after the earthquake played an important role in enabling residents to evacuate quickly to safer locations, thereby limiting tsunami-related fatalities [3].

A similar pattern was observed in Tonga prior to the . On January 14, 2022, unusual ocean behaviour detected by tide gauges in Nukuʻalofa prompted the Tonga Meteorological Service to issue a marine tsunami warning. Although the advisory was later cancelled, the warning increased community vigilance along the coast. When the actual tsunami arrived the following day, many residents were already alerted to changing sea conditions and evacuated quickly [4]. While Tonga’s coastal population is far smaller and less densely populated than that of Japan, the event nonetheless illustrates how early warnings and public responsiveness can reduce tsunami-related mortality even during rapidly evolving hazards.

These cases suggest that timely and well-understood early warnings can support prompt evacuation and help reduce tsunami-related fatalities, particularly within the context of complex and fast-onset hazard.

Tsunami Awareness and Environmental Cues

While early warning systems rely on technology and institutional monitoring, tsunami survival does not depend on technology alone. In many cases, individuals must assess risk and decide to evacuate even when formal warnings are delayed, cancelled, or unavailable. In this context, tsunami awareness and the ability to recognise environmental warning signs become critically important.

Tsunami awareness plays a key role in enabling residents to evacuate independently. When coastal communities are familiar with tsunami risks and warning signs, individuals are more likely to act quickly and move to safer areas without waiting for official instruction.

Across several tsunami events examined during this research, environmental cues served as decisive triggers for evacuation. During the Hunga Tonga–Hunga Haʻapai eruption, the arrival of moderate tsunami waves prompted residents to evacuate after the earlier warning had been cancelled [4]. In nearby Aotearoa New Zealand, mariners observed rough seas and submerged boats associated with tsunami waves generated by the same eruption, leading them to flee to higher ground [5].

Similar behavior was documented during the 2018 between the major islands of Java and Sumatra in Indonesia, where residents reported hearing unusual sounds from the ocean and observing the arrival of the initial wave, prompting immediate evacuation [6]. In contrast, the 2018 , on the Northern peninsula of Minahasa in Indonesia, highlights the consequences of disrupted communication and limited awareness. Power outages following the earthquake meant that many residents did not receive evacuation alerts, contributing to a high death toll of approximately 4,340 fatalities and more than 10,000 injuries [7].

These cases highlight a simple but powerful pattern: when people know what warning signs to look for, they do not always need to rely on official systems to take life-saving action.

Tsunami Awareness Activities and Evacuation Drills

While individual awareness is essential, it is often strengthened through organised education and preparedness efforts. Tsunami awareness campaigns and evacuation drills help transform knowledge into action by familiarising communities with evacuation routes and appropriate responses.

In Ishikawa Prefecture off the Sea of Japan, evacuation drills conducted twice annually were identified as an important factor in reducing fatalities during tsunami events. Regular drills ensured that residents were familiar with evacuation procedures and could act quickly and efficiently when warnings were issued [3].

Similarly, prior to the Hunga Tonga–Hunga Haʻapai tsunami, Samoa and Tonga had engaged in tsunami outreach and education initiatives since the 2009 Samoa–Tonga tsunami. Just two months before the event, was commemorated through a range of community-based activities which included tsunami themed art and poetry competitions in schools, informative discussions broadcasted on radio and tsunami-focused prayers and preparedness announcements during church services. Research notes that these ongoing efforts played a significant role in reducing casualties by improving public understanding of tsunami behaviour and appropriate responses [4].

These examples demonstrate how repeated education and practice can reinforce awareness and support effective evacuation during tsunami events.

Conclusion

In conclusion, the tsunami case studies reviewed in this article demonstrate the critical role of DRR in influencing evacuation outcomes and human impact during tsunami events. Early warning systems, public awareness, recognition of environmental cues, and regular evacuation each support timely and effective evocation, contributing to reduced fatalities. While no single strategy is sufficient on its own, these findings highlight the importance of multifaceted and well-implemented DRR approaches.

– Abraham Alexander

References

[1] United Nations Office for Disaster Risk Reduction (UNDRR). Disaster Risk Reduction Terminology.

[2] Prevention Web. Disaster Risk Reduction and Disaster Risk Management: Key Concepts.  

[3] Suppasri, A., Kitamura, M., Alexander, D., Seto, S., & Imamura, F. (2024). The 2024 Noto Peninsula Earthquake: Preliminary Observations and Lessons to be Learned. International Journal of Disaster Risk Reduction, 110. .

 [4] Borrero, J. C., Cronin, S. J., Latu’ila, F. H., Tukuafu, P., Heni, N., Tupou, A. M., Kula, T., Fa’anunu, O., Bosserelle, C., Lane, E., Lynett, P., & Kong, L. (2022). Tsunami Runup and Inundation in Tonga from the January 2022 Eruption of Hunga Volcano. Pure and Applied Geophysics. .

[5] Harrison, S. E., Lawson, R. V., Kaiser, L., Potter, S. H., & Johnston, D. (2025). Understanding mariners’ tsunami information needs and decision-making contexts: A post-event case study of the 2022 Tonga eruption and tsunami. IScience, 28(2), 111801. .

[6] Takabatake, T., Shibayama, T., Esteban, M., Achiari, H., Nurisman, N., Gelfi, M., Tarigan, T. A., Kencana, E. R., Fauzi, M. A. R., Panalaran, S., Harnantyari, A. S., & Kyaw, T. O. (2019). Field survey and evacuation behaviour during the 2018 Sunda Strait tsunami. Coastal Engineering Journal, 61(4), 423–443. .

[7] Harnantyari, A. S., Takabatake, T., Esteban, M., Valenzuela, P., Nishida, Y., Shibayama, T., Achiari, H., Rusli, Marzuki, A. G., Marzuki, M. F. H., Aránguiz, R., & Kyaw, T. O. (2020). Tsunami awareness and evacuation behaviour during the 2018 Sulawesi Earthquake tsunami. International Journal of Disaster Risk Reduction, 43, 101389. .  

The post Before the Wave Arrives: Disaster Risk Reduction and Tsunami Events appeared first on The Disaster Lab.

I am writing this post on a morning when up to 50 centimetres of snow are forecast to fall on the city of Ottawa (from “adawe” in Algonquin meaning “trade”).

I am also writing on a morning when the world continues to confront the deadly Covid pandemic, and where we are processing the news of a deadly , and tragic . In other words, the themes that animate the work of the Disaster Lab (migration, the environment, the personal and the intimate) are feeling very present.

It has been a busy first year for the project and I am grateful to the amazing team of research assistants who are making the vision for this project a reality. Over the past few months, the team has combed the to identify 345 cases where some kind of disaster has struck and required the movement of people. This has sometimes involved a short-term evacuation and in other cases, the relocation has been more permanent.

The team has done an amazing job of sourcing materials to enrich the information provided in the database and we are already getting a sense of some of the larger research themes that we’ll be able to take up moving forward. These include the particular histories of disaster attending Indigenous communities. The Red Earth First Nation (Red River First Nation) in Saskatchewan comes to mind as it is a community that has endured four devastating floods over a ten-year span, demonstrating that perhaps Indigenous communities do not receive proper disaster mitigation measures and attention from authorities. Themes have also emerged in terms of the complicated federal / provincial landscape when it comes to declaring states of emergency and developing appropriate responses; part of this is fiduciary, ethical and governmental in nature.

We are discovering each day that there is much to be learned in terms of how solutions have been imagined. Helen Kennedy, who is a PhD Candidate in the Department of History at ĐÓ°ÉÔ­´´, has been tracking some of this work in terms of Red Cross relief efforts and has made the pointed observation that the organization only really began to talk about the particular plight of Indigenous communities in the 1990s. Helen will be offering additional insights on her research in this space in the weeks to come but attending to histories of mobility, displacement and disaster relief amongst Indigenous communities is certainly going to be central to the work of the project moving forward.

One of the challenges we have identified is the difficulty of tracking long-term disasters over the easily identifiably acute disasters that we see, for example, when looking at floods and fires. The Canadian Disaster Database is useful for heightened moments of crisis but there is nothing in the database that speaks to the “dust bowl” of the 1930s, for example, when economic depression and droughts led to the migration of thousands. Similarly, the database doesn’t let us see climate change as a whole though in documenting the fires and over the past two years, we certainly had a sense that these events were part of a larger picture.

As this new year begins, we are therefore thinking about what has been accomplished as well as the work that lies ahead. It was particularly gratifying to spend time with students in the Ottawa ĐÓ°ÉÔ­´´ District School Board in November. Working with Grade 10 teacher Emma McLean, Valerie Wood and Arden Hody developed an interactive workshop based on their research with the Canadian Disaster Database, giving the students a chance to parallel some of their research. We loved hearing about the students’ responses and the fact that they picked up really clearly on the messy divide between human and natural disasters, as well as the close relationship between geography and history as disciplines. The students are going to stay involved in the project as they take up some ArcGIS mapping activities based on the longitudinal and latitudinal data put together by Rebecca Lloyd from the project team. We are excited to have a sense of what all this looks like!

In other words, it’s going to be another busy year for the Disaster Lab but we are looking forward to really getting into some of the themes identified so far and we look forward to sharing more of our findings in the near future.

– Dr. Laura Madokoro

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