Six Years After Tsunami Japan is Finding Ways to Work with Nature

BY EDM | 30 MAR 2017
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Exploring the “multiple-lines of defense” approach to managing tsunami risk
March 11, 2017 marked the sixth anniversary of the Great East Japan Earthquake and Tsunami, also known as the Tohoku Earthquake and Tsunami. In 2011, a magnitude 9.0 earthquake struck near the northeastern coast of country, triggering a massive tsunami and a nuclear meltdown at the Fukushima Daiichi Nuclear Power Plant. The combined impacts of these events led to widespread flooding and devastation along the coast with over 1 million buildings destroyed and the combined total of confirmed deaths and missing is more than 22,000 (nearly 20,000 deaths and 2,500 missing).[1]

While the nation of Japan works to rebuild its communities and coast, questions about various options and strategies for doing so remain a challenge. While planning, design, and reconstruction is underway, the extent of the tsunami damage has meant that the reconstruction process will continue for the near future. The Government of Japan has promoted a “multiple-lines of defense” approach to managing tsunami risk including structural and nonstructural coastal flood management methods and changes in land use management.


Coastal Defenses


A key element of this defense strategy is the planned construction of 250 miles (405 kilometers) of concrete seawalls and dikes along the coast in the three prefectures primarily affected - Fukushima, Iwate and Miyagi.[2] In some places, the walls are expected to be 14 m (45 ft) tall and 45 m (150 ft) wide.[3] As of January 2017, 22% of this system had been completed and the plan has been met with widespread skepticism including by a number of academics, environmental organizations, and community members that voiced concern that building the wall would miss an important opportunity to rebuild in a way that restored coastal habitat and maintained residents connection to the coast where it still existed. [4] Of particular concern to some scientists was the damage that seawall construction could cause to the flora and fauna that was already making a recovery in disaster-affected areas and in the new marsh habitats created by the tsunami.[5]

In some cases, seawalls and dikes can promote a false sense of security for coastal residents, damage coastal ecosystems during construction, and can cause coastal erosion after they are constructed further degrading the protective functions of coastal natural habitat. Hardening of the coastline can also affect tourism and fisheries by limiting access to the coastline for recreation and destroying or damaging fish habitat.

The "Morino-Bochoutei"(translation Green Tide Embankment Project), a local nonprofit, proposed an alternate approach to build lower mounds with disaster debris and plant the landside of the embankment with native tree-species that had survived the tsunami. However, due to the lack of evidence supporting the effectiveness of this approach, the government rejected it as a viable replacement and instead piloted the approach in a small section of the newly constructed barrier system.[6]

While the extensive system of seawalls is a large component of the post-tsunami reconstruction plan, a number of other local and national government and nonprofit initiatives promote the use of non-structural and natural based approaches to providing coastal protection.

One of the alternative initiatives is the Millennium Hope Hills project, which is a park system that will provide an evacuation area and buffer against tsunami impacts through a system of engineered tree-covered mounds and elevated pathways. Situated near the Sendai Airport along the Tenzen Canal on 47 ha of land, the parks will create 15 evacuation mounds (10 m high) using non-toxic disaster debris. The first park, Ainokama Park, has been completed and thousands of native, fast-growing tree saplings have been planted. The park also includes a memorial dedicated to the Great East Japan Earthquake and Tsunami that also promotes tsunami awareness and education.

Another alternative example is the restoration of the coastal forest belt designed to buffer tsunami impacts. The coastal forest was largely destroyed in the tsunami, but the trees with a root depth of greater than 3 meters were found to be better able to withstand the force of the waves.[7] As a result, replanted trees will be on elevated mounds to create additional room for the roots to take hold as well as provide an additional buffer against tsunamis and debris. The government envisions that this coastal forest will serve as a secondary line of defense after the seawalls.


Coastal Livelihoods


In the months following the tsunami, WWF-Japan began working to improve coastal livelihoods and fisheries. The Nature and Livelihood Recovery Project, a five-year project, included natural environment, marine pollution, and fishery economics surveys. The project studied two model areas, Minamisanriku Town (Shizugawa Bay) in Miyagi Prefecture and Soma City (Matsukawaura Lagoon) in Fukushima Prefecture and found that coastal species and habitats were recovering, and disaster debris, such as concrete rubble along the coast, was providing a spawning ground for young fish.[8] The project report however also concluded that environmental regeneration did not appear to be a priority for local governments.[9]

The Japan recovery and reconstruction experience highlights some of the challenges associated with integrating natural and nature-based approaches into disaster management. The environmental, social, and economic benefits of investments such as coastal forests, parks, and natural spaces—particularly in urban areas—are well documented, but understanding how these measures preform as a disaster risk reduction method at a large-scale or in combinations with hard engineering needs further research, analysis, and documentation.

 
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[1] Japanese Red Cross Society and International Federation of Red Cross and Red Crescent Societies, Japanese Red Cross Society Disaster Response and the Fukushima Daiichi Nuclear Power Plant Accident,  http://reliefweb.int/sites/reliefweb.int/files/resources/1305600-JRCS%20Fukushima%20case%20study-EN-LR.pdf; CNN, “2011 Japan Earthquake - Tsunami Fast Facts,” March 5, 2017. http://www.cnn.com/2013/07/17/world/asia/japan-earthquake---tsunami-fast-facts/

[2] Japan Today, “22% of Seawall Building Finished in areas Hit by 2011 Tsunami”, (Tokyo, Japan), March 11, 2017.

[3] Winifred Bird, “In Post-Tsunami Japan, A Push To Rebuild Coast in Concrete,” Yale Environment 360, http://e360.yale.edu/features/in_post-tsunami_japan_a_push_to_rebuild_coast_in_concrete

[4] Japan Today, “22% of Seawall Building Finished in areas Hit by 2011 Tsunami”, (Tokyo, Japan), March 11, 2017; Winifred Bird, “In Post-Tsunami Japan, A Push To Rebuild Coast in Concrete.”

[5] Ibid.

[6] A. Strusinska-Correia, “Tsunami mitigation in Japan after the 2011 T?hoku Tsunami,”  International Journal of Disaster Risk Reduction (2017), http://dx.doi.org/10.1016/j.ijdrr.2017.02.001

[7] David Cyranoski, “Rebuilding Japan: After the Deluge,” Nature 483 (2012): 141–143. http://www.nature.com/news/rebuilding-japan-after-the-deluge-1.10172

[8] WWF-Japan, WWF Japan Report on the Nature and Livelihood Recovery Project, http://www.wwf.or.jp/activities/files/20131129shinsai_en.pdf

[9] Ibid.

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