STUDY ON TSUNAMI REDUCTION EFFECTS OF BUILDINGS ALONG COASTS

Abstract

 A full-scale three-dimensional numerical analysis is carried out to quantitatively determine whether rigid buildings located along coasts reduce inundation water volume due to run-up tsunamis. For investigation, a run-up tsunami propagating through impermeable rigid buildings on an impermeable horizontal flat land behind an impermeable vertical quay wall is simulated and analyzed in terms of inundation water volume beyond the buildings using a three-dimensional coupled fluid-structure-sediment interaction model. Numerical results show that the inundation water volume decreases with an increase in the ratio of the longshore length of the buildings to the total length of the coastline (building-coastline ratio), and conversely slightly rises with an increase of the height of the tsunami and the cross-shore distance of the buildings from the quay wall. On the other hand, the inundation water volume is insensitive to the period of the tsunami, the height of the quay wall, the initial sea water level, the cross-shore length of the buildings, and the number of gaps between the buildings. Based on the numerical results, approximation equations are proposed to predict the reduction rate of the inundation water volume from the building-coastline ratio. As a result, it is demonstrated that rigid buildings located along coasts are effective as one of the countermeasures against run-up tsunamis in terms of inundation water volume.