Tsunami Disasters and Global Heating in Japan: Incremental or Transformational Adaptation to Sea Level Rise?

Joel Littler
Peter Matanle
Oliver Slay

The entrance to Tarō’s ria, showing a bank of tetrapods, reconstructed since 2011. The ria topography increases the height and speed of tsunami, making the Sanriku coastline of Iwate prefecture especially prone to tsunami disasters.

Global heating is transforming our world. One of the most serious effects has been an increase in the frequency and severity of disasters, due to the impact of climate change as a ‘threat multiplier’ (USDOD, 2010). The UN estimates that currently there is one climate crisis related disaster occurring somewhere on Earth every week, and these are occurring more regularly and sooner than previously anticipated (Harvey, 2019).

Richer developed countries certainly have the resources and capabilities for adapting to the climate crisis by strengthening and transforming their disaster defences; but are they preparing adequately for what is to come? Do we know enough about how climate breakdown affects disasters and our ability to respond, and how these impacts will intensify in the future? Indeed, global heating itself is a disaster; a long-run event carrying heavy and ongoing socio-environmental costs.

Among developed countries Japan is particularly prone. Its location in the Pacific Ring of Fire means that earthquakes and volcanic eruptions occur on a regular basis throughout the archipelago. And the presence of deep ocean trenches along the eastern side of the archipelago means that Japan is vulnerable to giant tsunami generated by megathrust earthquakes. With Asia’s fastest ageing and shrinking population, Japan’s small and isolated rural and coastal communities are also becoming more vulnerable to the impacts of disasters (Matanle, 2011).

Tsunami and Sea Level Rise

One of the main outcomes of global heating is sea level rise due to thermal expansion of the oceans and the melting of the polar ice sheets and mountain glaciers. Estimates of the rate of sea level rise are regularly revised, usually upwards, as knowledge of ice sheet melting and analogous paleoclimatic conditions accumulates (Hansen et al, 2016). Indeed, recent studies confirm that ice-melt and sea level rise are accelerating (IMBIE Team, 2018; Nerem et al, 2018; Rahmstorf, 2007), and the UN Intergovernmental Panel on Climate Change has once more recently revised its projections (IPCC, 2019).

In the aftermath of the 11 March 2011 Great East Japan Earthquake and tsunami disaster, the word sōteigai (‘beyond expectations’; ‘unimaginable’) was used by the Japanese government and Tokyo Electric Power Company to explain their failure to prevent the Fukushima nuclear disaster (Samuels, 2013, 104). This claim has been much criticised since, given the circumstances leading up to that disaster (Matanle, 2011).

So, we decided to research whether the Japanese authorities are imagining the next giant tsunami that will strike the north-eastern Tōhoku region. In particular, we asked whether global heating driven sea level rise was taken into account in the planning and design of the tsunami defence infrastructure now nearing completion, or whether sea level rise needs to be considered (Matanle, Littler & Slay, 2019).

A Google Earth image prepared by the authors of Tarō taken on 9 January 2016 with the town’s basic reconstruction plan superimposed.

What Did We Find Out?

The Japanese government responded to the disaster of 11 March 2011 by constructing and strengthening a series of 440 seawalls (Films 1 & 2). At nearly 400km, they connect with natural formations along the coast of the three eastern prefectures of Tōhoku — Iwate, Miyagi and Fukushima — to form a single barrier against the destructive tsunami that frequently strike the region. The seawalls, up to 15.5m high in places, obscure the sea from the towns, which some say increases the vulnerability of populations.

We looked into the reconstructed tsunami defences at Tarō, a town located in the northern part of the picturesque Sanriku region in Iwate Prefecture. Prior to 2011 Tarō was famous for its 2.4 kilometres of seawall of between 10 and 13.7 metres in height that completely obscured the sea, constructed in the wake of the Meiji Sanriku tsunami of 1896 and the Shõwa Sanriku tsunami of 1933. These seawalls, at one time the strongest tsunami defences in Japan, were destroyed in 2011, along with all but one of the manmade defences in eastern Tōhoku. There is anecdotal evidence to suggest that the seawalls gave citizens a false sense of security and therefore increased their vulnerability.

Due to the potentially sensitive nature of our findings we triangulated multiple different research methods for ensuring verification and accuracy. This included five site visits to Tōhoku between 2011 and 2017, with participant observation and interaction; interviews and information checks with Japanese local and central government officials and geological scientists; a systematic review of central and local government planning documentation; and historical near-Earth composite imagery and ground level photographic observation.

The reduction in Tarō’s death rate from 83.9% of its population in 1896, through 32.5% in 1933, to 3.9% in 2011, demonstrates significant improvements in disaster risk reduction being achieved by the Japanese authorities, particularly in combining physical sea defences with soft-infrastructure, such as the utilisation of social capital and disaster preparedness drills. Nevertheless, we question whether, by constructing defences to prevent a recurrence of the previous disaster, the authorities are adequately imagining and preparing for a transformed future.

To find out whether sea level rise was being taken seriously by the authorities in their disaster prevention planning, we downloaded and analysed 181 municipal, prefectural and national post-tsunami recovery and reconstruction planning documents and interviewed officials from the Reconstruction Agency. Using key words related to climate change and sea level rise we ran the documents through computational analysis and found one mention of climate change driven sea level rise. There were 96 mentions of global warming in 19 documents, but none associated climate change with sea level rise, nor was there any connection between sea level rise and tsunami defence infrastructure. Moreover, interviews with government officials and geological scientists confirmed that global heating driven sea level rise has not been included in scenario modelling for future tsunami in Tõhoku, despite the region being a known hazard zone for giant tsunami from undersea megathrust earthquakes.

The new defences in Tarō are an incremental strengthening of the pre-existing defences to 14.7m in height, and with the addition of a new port wall. This should improve safety still further. However, the fishing cooperative’s port tower measures the height of the 2011 tsunami at 17m (Photo 1). With the addition of sea level rise there is potential for the next tsunami to overtop the new defences by up to four metres, or more. Even though the walls are designed to be overtopped by the largest tsunami, there is a possibility that by not including sea level rise as an additional transformational risk factor the defences will be overwhelmed, just like in 2011. In addition to the walls, residential areas are being moved to higher ground in a new development on a nearby hill and the main area of the town, which was destroyed in 2011, will be public and private amenities such as shopping, sports and leisure facilities.

The Tarō fishing cooperative port tower. The yellow indicators show the heights of the 1896, 1933 and 2011 tsunami at that location, with the latter showing 17m. Peter Matanle is standing at the bottom of the tower for scale.

Implications

The potential for sea level rise to reduce the effectiveness of tsunami defences has not yet been fully taken into account in Japan. The seawalls under construction in Tōhoku are designed to be effective through to the early 22nd century, by which time current climate projections predict sea level rises of 0.5m by 2060 and up to 1m or more by 2100 (IPCC, 2019), and despite recent research indicating that sea level rise will increase the height, inundation area, and destructive power of tsunami (Dominey-Howes & Goff, 2013; Li et al, 2018).

Japan is facing the combined 21st century challenges of ageing, depopulation and global heating. It is in the vanguard of a transformation to a new post-growth order in Asia and therefore an example for other countries potentially to emulate as they enter their own post-growth pathways (See: DeWit, 2015; Matanle, 2017). However, the Japanese authorities are adopting an incremental approach to disaster prevention in Tōhoku in circumstances which require a transformational vision (Kates et al, 2012). With its reluctance to imagine the consequences of climate change and how it might affect tsunami disasters, the Japanese state demonstrates that it is yet to seize the opportunity to lead Asia. Instead, and unfortunately, the 20th century Construction State (Feldhoff, 2002; McCormack, 2002) and its logic of modern developmentalism as a defensive bulwark against the assumed destructive encroachments of nature remains in place, and is long past its use-by date.

It is disconcerting for us to observe the lack of acknowledgement of sea level rise among governments and engineers, whilst planning projects intended to last for more than 50 years. It is important to note that Japan is not exceptional in this regard. However, humanity has a limited time window to mitigate and adapt to the impacts of global heating. We have known for many decades, if not a century or more, that environmental systems are sensitive to human activity, and that positive feedback loops can exacerbate and accelerate changes already under way. In the 21st century, as younger people imagine a much-altered future for themselves, we would all do well to heed the warnings from science and nature.

The full research report can be found, here: https://apjjf.org/2019/13/Matanle.html

About the Authors

Joel Littler is Lecturer at the Pridi Banomyong International College, Thammasat University, Thailand, and a graduate of the School of East Asian Studies, University of Sheffield (BA, Japanese Studies, 2016), and Pembroke College, University of Oxford (MSc with Distinction, Japanese Studies, 2017).
Contact: joel.l@pbic.tu.ac.th.

Peter Matanle is Senior Lecturer and Director of Research and Innovation at the School of East Asian Studies, University of Sheffield, UK. His research and teaching interests are in the social and cultural geography of the Asia-Pacific, focusing on Japan.
Contact: p.matanle@sheffield.ac.uk
University Profile Page
Twitter: @matapet

Oliver Slay is a PhD candidate in the Department of Bioscience and Chemistry, Sheffield Hallam University, UK. He is a graduate of the School of East Asian Studies, University of Sheffield (BA, Japanese and Korean Studies, 1993). After following a 20-year career in IT administration and software development (bespoke GIS/mapping software), he completed a BSc and MSc (Hallam) in Molecular and Cell Biology.

Acknowledgements

The authors would like to thank the Japan Foundation Endowment Committee for fieldwork funding for this research, and Professor Kenji Tani of Saitama University for use of topographic data from his website.

References

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