Can Small Islands Protect Nearby Coasts From Tsunamis? An Active Experimental Design Approach

TL;DR

This study investigates whether small islands can protect coasts from tsunamis by analyzing run-up amplification through numerical simulations and an emulator to optimize the exploration of physical parameters.

Contribution

It introduces a novel experimental design using Gaussian Process emulators to efficiently identify conditions leading to maximum tsunami run-up amplification near small islands.

Findings

Run-up amplification can be significantly higher behind small islands.

The emulator effectively guides parameter exploration, reducing the number of simulations needed.

Physical parameters like island slope and wave wavelength influence run-up amplification.

Abstract

Small islands in the vicinity of the mainland are believed to offer protection from wind and waves and thus coastal communities have been developed in these areas. However, what happens when it comes to tsunamis is not clear. Will these islands act as natural barriers ? Recent post-tsunami survey data, supported by numerical simulations, reveal that the run-up on coastal areas behind small islands was significantly higher than on neighboring locations not affected by the presence of the island. To study the conditions of this run- up amplification, we solve numerically the nonlinear shallow water equations (NSWE). We use the simplified geometry of a conical island sitting on a flat bed in front of a uniform sloping beach. By doing so, the experimental setup is defined by five physical parameters, namely the island slope, the beach slope, the water depth, the distance between the island and the plane beach and the incoming wavelength, while the wave height was kept fixed. The objective is twofold: Find the maximum run-up amplification with the least number of simulations. To achieve this goal, we build an emulator based on Gaussian Processes to guide the selection of the query points in the parameter space.