2014 Volume 5 Issue 1 Pages 77-81
Large-scale infrastructure for tsunami damage mitigation includes tidewater control forests and tide embankments. It is said that installing a tidewater control forest of 200 m in width along the coast is effective in mitigating tsunami damage. Since the East Japan Great Earthquake, tide embankments of about 7 m high have been under construction on coasts of tsunami-hit areas. Restoration and installation of tidewater control forests require many years, and the construction of large-scale tide embankments requires enormous cost. This study focuses on existing roads in the coastal areas. We investigated the effects of road, depending on their conditions of spacing, on tsunami sand deposition. A 0.3 m-wide, 12 m-long open channel was used for tsunami experiments. To simulate a tsunami, a removable barrier was set near the upstream end of the channel to retain water. The barrier was lifted suddenly to generate a bore. The scale of the model was 1/100. A certain amount of sand and models of a tidewater control forest, a tide embankment and roads made of acrylic were placed at the longitudinal midpoint of the channel. The movement of sand carried by the reproduced tsunami was observed. Several combinations of the tidewater control forest, tide embankment and three roads were used in the tsunami reproduction experiment, with the spacing changed for each experiment. As the result of experiments, it was clarified that when the spaces between the roads were wide, the amount of deposited sand was controlled better. It was also clarified that the amount of sand deposition at the time of a tsunami in a coastal area was able to be controlled effectively by combining roads with wide spacing between them with a tidewater control forest or a tide embankment.
