Abstract
In coastal farmlands, farm roads and farmland serve to dissipate the energy of the tsunami in stages. The role of drainage channels in spreading and draining a tsunami flood should also be considered. The energy dissipation characteristics of a drainage channel and sidewall behind a coastal levee were evaluated in this paper. The sidewall was installed either on the coastal side or on the inland side of the channel bank. A tsunami that overflowed the coastal levee washed the back slope of the levee by supercritical flow. The tsunami that reached the beginning of the inland zone generated a hydraulic jump, the location of which moved to the coastal levee. A comparison of the distribution of the bottom velocity in case of the drainage channel with or without sidewall yielded the following results: 1) In the region of small volume of overflowed tsunami, the drainage channel without sidewall dissipates the energy of the tsunami. However, a drainage channel with a wide cross section is required for a large volume. 2) The sidewall effectively dissipates tsunami energy, and the effect varies with the location of the sidewall.
