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Increasing societal resilience to tsunami risk


By Dr. Rosa Sobradelo and Shigeko Tabuchi | August 5, 2019

Through the Willis Research Network (WRN), Willis Re has worked closely with Tohoku University in Japan since 2010, improving the understanding and quantification of tsunami risk in south-east Asia. We provide an update on the recent research focus: assessment of multi-layered tsunami countermeasures; and insights into "black" tsunamis.

Professor Fumihiko Imamura, Director of Tohoku University’s International Research Institute of Disaster Science (“IRIDeS”) and members in his laboratory have conducted research into tsunami data collection, tsunami simulation, as well as the development of tsunami hazard maps and vulnerability functions.

Recently, our joint research has focused on the following two topics: multi-layered tsunami countermeasures and "black" tsunamis

  1. Assessing the performance of multi-layered tsunami countermeasures before and after the 2011 Great Japan Tsunami

    The 2011 Japan tsunami, with a wave more than 10m overtopping breakwaters and seawalls, destroyed properties, infrastructure and coastal pine forests but was largely blocked by the embankment-type expressway located at approximately 3 km from the shore. The idea of “multi-layered tsunami countermeasures” has been developed as one of the lessons from the 2011 tsunami. For example, Sendai City is now constructing a 6m elevated road at 1 km parallel to the sea as further mitigation to the tsunami power. We have quantitatively evaluated such mitigation effect in Sendai City, and other areas potentially at risk of Nankai Trough tsunami (Wakayama, Tokushima and Kochi cities). Reduced loss of life and property losses in areas with such countermeasure are expected as it is generally observed that tsunami inundation area can be reduced by up to 30%, and the tsunami arrival time can be delayed by up to 10 min.
  2. Multi-sectoral collaboration to quantify the impacts of "black tsunamis"

    Kawasaki City is one of the large cities in the Kanto region, with a large concentration of large companies and factories. Tohoku University collaborated with the University of Tokyo, Kawasaki City and Fujitsu to better understand and quantify the impacts of a "black" tsunami: images of the 2011 tsunami show it as “black” because the water contained sludge, mud and other hazardous substances. “Black” tsunamis have mid to long-term effects on health conditions of tsunami victims, for example very fine sediments would cause pneumonia or brain abscess. Our advanced tsunami simulation techniques revealed a high risk of the black tsunami in Kawasaki City. Our tsunami evacuation simulations highlighted areas with severe traffic, high occupancy of evacuees as well as expected numbers of casualties. Life insurance loss could then be quantitatively assessed by applying various tsunami scenarios together with various tsunami countermeasures and disaster awareness/preparedness of residents. These allow us to create realistic and research-based property and casualty tsunami Realistic Disaster Scenarios that can be used for reinsurance, portfolio optimisation, and creating our own view of risk.

Tohoku University will present at the 2nd World Bosai Forum in Sendai in November.


Dr. Rosa Sobradelo
Senior Research Manager

Rosa is a Senior Research Manager for the Willis Research Network where she manages the Earth Risk Hub. That is to say research activities in the areas of geological risks such as tsunami, volcanic and earthquake risk with leading academic partners around the world, matching them with business needs to derive tangible outputs to improve our client services. She also works on consultancy projects relating to volcanic hazard and risk. She is a statistician at heart, with a PhD in Applied Statistics and Operations Research from the Polytechnic University of Catalunya, an MSc in Mathematics, Statistics and Operations Research from New York University, and a BSc in Business Administration from University of Santiago de Compostela, and has made a career out of risk building probabilistic models for Health, Finance and Catastrophe Risk.

Shigeko Tabuchi
Executive Director

Shigeko is an Executive Director in Willis Re. She has a long experience in developing catastrophe models, including our Algeria earthquake model for ACIP, our Turkey earthquake model for TCIP and most recently our Japan tsunami model. Shigeko joined Willis Re in 1997 with a Master’s Degree in Civil Engineering from Imperial College, London.

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