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Natural Hazards and Earth System Sciences An interactive open-access journal of the European Geosciences Union
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Volume 18, issue 1 | Copyright
Nat. Hazards Earth Syst. Sci., 18, 145-155, 2018
https://doi.org/10.5194/nhess-18-145-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 10 Jan 2018

Research article | 10 Jan 2018

Developing fragility functions for aquaculture rafts and eelgrass in the case of the 2011 Great East Japan tsunami

Anawat Suppasri1, Kentaro Fukui2, Kei Yamashita1, Natt Leelawat3, Hiroyuki Ohira4, and Fumihiko Imamura1 Anawat Suppasri et al.
  • 1International Research Institute of Disaster Science, Tohoku University, 468-1 Aramaki-aza Aoba, Aoba-ku, Sendai 980-0845, Japan
  • 2Kanagawa Prefectural Office, 1 Nihon Odori, Naka-ku, Yokohama 231-8588, Japan
  • 3Department of Industrial Engineering, Faculty of Engineering, Chulalongkorn University, Phayathai Road, Pathumwan, Bangkok 10330, Thailand
  • 4Electric Power Development Co., Ltd., 6-15-1, Ginza, Chuo-ku, Tokyo 104-8165, Japan

Abstract. Since the two devastating tsunamis in 2004 (Indian Ocean) and 2011 (Great East Japan), new findings have emerged on the relationship between tsunami characteristics and damage in terms of fragility functions. Human loss and damage to buildings and infrastructures are the primary target of recovery and reconstruction; thus, such relationships for offshore properties and marine ecosystems remain unclear. To overcome this lack of knowledge, this study used the available data from two possible target areas (Mangokuura Lake and Matsushima Bay) from the 2011 Japan tsunami. This study has three main components: (1) reproduction of the 2011 tsunami, (2) damage investigation, and (3) fragility function development. First, the source models of the 2011 tsunami were verified and adjusted to reproduce the tsunami characteristics in the target areas. Second, the damage ratio (complete damage) of the aquaculture raft and eelgrass was investigated using satellite images taken before and after the 2011 tsunami through visual inspection and binarization. Third, the tsunami fragility functions were developed using the relationship between the simulated tsunami characteristics and the estimated damage ratio. Based on the statistical analysis results, fragility functions were developed for Mangokuura Lake, and the flow velocity was the main contributor to the damage instead of the wave amplitude. For example, the damage ratio above 0.9 was found to be equal to the maximum flow velocities of 1.3ms−1 (aquaculture raft) and 3.0ms−1 (eelgrass). This finding is consistent with the previously proposed damage criterion of 1ms−1 for the aquaculture raft. This study is the first step in the development of damage assessment and planning for marine products and environmental factors to mitigate the effects of future tsunamis.

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We developed fragility functions of aquaculture rafts and eelgrass based on damage data and numerical simulation of the 2011 Great East Japan tsunami. These fragility functions explain damage characteristics of both items against tsunami flow velocity. By understanding these characteristics, damage estimation and loss assessment as well as marine/fishery disaster mitigation plan and management in other areas of the world from future tsunamis can be implemented.
We developed fragility functions of aquaculture rafts and eelgrass based on damage data and...
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