Systematic Evaluation of Different Infrastructure Systems for Tsunami Defense in Sendai City

Kwanchai Pakoksung,Fumihiko Imamura,Anawat Suppasri

doi:10.3390/geosciences8050173

Abstract

The aim of this study is to assess the performances of different infrastructures as structural tsunami countermeasures in Sendai City, based on the lessons from the 11 March 2011, Great East Japan Tsunami, which is an example of a worst-case scenario. The tsunami source model Ver. 1.2 proposed by Tohoku University uses 10 subfaults, determined based on the tsunami height and the run-up heights measured for all tsunami affected areas. The TUNAMI-N2 model is used to simulate 24 cases of tsunami defense in Sendai City based on a combination of 5 scenarios of structural measures, namely, a seawall (existing and new seawall), a greenbelt, an elevated road and a highway. The results of a 2D tsunami numerical analysis show a significant difference in the tsunami inundations in the areas protected by several combinations of structures. The elevated road provides the highest performance of the single schemes, whereas the highest performance of the 2-layer schemes is the combination of an existing seawall and an elevated road. For the 3-layer scenarios, the highest performance is achieved by the grouping of an existing seawall, a new seawall, and an elevated road. The combination of an existing seawall, a new seawall, a greenbelt and an elevated road is the highest performing 4-layer scenario. The Sendai City plan, with a 5-layer scenario, reduces the tsunami inundation area by 20 sq. km with existing structural conditions. We found that the combination of an existing seawall, a greenbelt, an elevated road and a highway (a 4-layer scheme) is the optimum case to protect the city against a tsunami similar to the 2011 Great East Japan Tsunami. The proposed approach can be a guideline for future tsunami protection and the evaluation of countermeasure schemes.

Highlights

Introduction11 March 2011, affecting human lives and causing economic losses
A magnitude 9.0 earthquake generated a huge tsunami in the Tohoku region of Japan on11 March 2011, affecting human lives and causing economic losses
In addition to the actual structures, their heights are represented in the terrain data, and the hypothetical structures were recommended by the plan to protect Sendai City against tsunamis

Summary

Introduction

11 March 2011, affecting human lives and causing economic losses. The affected area was recorded as approximately 561 sq. Km and covered 3 prefectures (Iwate, Miyagi, and Fukushima) along the Pacific coast of Japan [1,2]. The maximum recorded tsunami run-up height was approximately 40 m located in. The fatality number reported by the National Police Agency was approximately. 15,866 people, with approximately 2946 people missing [4]. The number of buildings and houses that collapsed or were washed away was approximately 130,411 [5,6]. The economic losses associated with the disaster were approximately 25 trillion yen, which was 30% of the national income of Japan in 2011 [7]. Approximately 82,000 people lost their houses [8]. The recovery efforts of the central and local government began, including the conceptual planning of the reconstruction of infrastructures including dike renovation, transportation, land-use zoning and urban relocation

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Conclusion