EFFECTIVENESS OF TSUNAMI MITIGATION STRUCTURES ON UNDERUTILIZED URBAN AREAS: A CASE STUDY ON REDUCING DAMAGE CAUSED BY TSUNAMI TO BUILDINGS

Resumen

There are concerns that a Nankai Trough Mega Earthquake may occur soon, and may cause widespread damage. This demands not only functional enhancement of seacoast environments, but also pre-disaster recovery planning that includes evacuation drills and securing evacuation sites in coastal areas. One of the most effective measures for this is relocation to higher ground in urban areas. However, financial restrictions and topographical conditions do not make relocation to higher ground easy. Thus, new countermeasures must be investigated that can facilitate early recovery and reconstruction. We believe that reducing the collapse and washing away of buildings due to tsunamis in densely populated areas could be one of the ways to approach this problem. Here, we find that the risk of building collapse and washing away depends on the type of building1) and inundation height. Thus, inundation due to tsunami must be lowered to avoid the low risk of collapse or wash away. Therefore, we look at the example2) of Miyagi Prefecture amid the lessons of the Great East Japan Earthquake, and expand upon the idea of multiple countermeasures to cover the urban areas. Specifically, low-lying underutilized lands in urban areas must be utilized to provide multifunction disaster prevention facilities enabling multiple countermeasures. Based on the above-mentioned points, the purpose of the present study is to propose multiple tsunami countermeasures for urban areas and numerically investigate their effects. Thus, we conducted a case study in a port town with a small river, which is an area where disasters are a concern.