Analysis of bay bathymetry elements on wave amplification: a case study of the tsunami in Palu Bay

This research was inspired by the deadly tsunami that struck Palu Bay, Sulawesi, Indonesia on September 28, 2018. High waves were observed not only at the bay's head but also in several other locations along the bay. This high amplification is most likely influenced by Palu Bay's bathymetry and the underwater sill in front of Palu City. The numerical simulations of the two-dimensional shallow water equations were used to investigate these aspects. The numerical scheme is validated first with analytical solutions of standing waves in a parabolic bay, as a model of Palu Bay. The results show a significant amplification at the bay's head, as a result of the bay's reduced cross-sectional area. Some amplifications were also observed along the channel sides, and the role of the underwater sill was also investigated. Next, we carried out simulations with the actual Palu Bay bathymetry and a hypothetical tsunami $N-$wave and/or Gaussian humps. The simulation result depicts extremely high waves recorded along the Palu Bay coastline, which is consistent with the field survey; additionally, the wave signal at Pantoloan corresponds reasonably well to the tide gauge data. These findings indicate that Palu Bay's bathymetry plays an important role in local wave amplification.

Automated summary

This research was inspired by the deadly tsunami that struck Palu Bay, Sulawesi, Indonesia on September 28, 2018, and focused on the impact of bathymetry and underwater obstacles on local wave amplification. Through numerical simulations and field surveys, it was found that the bathymetry of Palu Bay plays a crucial role in local wave amplification.