Effects of the Tsunami Countermeasures Focusing on the Tsunami Arrival Time in Kamakura

Abstract

While tsunami hazard maps show the expected maximum inundation depth, most of them do not show the minimum arrival time that is useful for considering evacuation plans and countermeasures. The objectives of the present study are thus to introduce a concept of an integrated tsunami minimum arrival time that can be used for considering evacuation strategy and countermeasures in order to maximize the least evacuation time among all the expected tsunamis. We applied this concept to the coastal area of Kamakura, Japan, as a case study and created maps for this integrated minimum time using an unstructured grid circulation model, FVCOM. We then considered three types of countermeasures (construction of elevated road, water gate, and elevated river wall) and evaluated them in terms of maximizing the expected least evacuation time and reducing the inundation area. This concept is considered to be useful for planning countermeasures because their effectiveness can be evaluated quantitatively. Key