Tsunami run-up amplification factors for real-time prediction of run-up heights and inundation distances for Penang Island

Abstract

The mega Indian Ocean tsunami that struck Malaysia on 26 December 2004 has awakened the attention of Malaysian government to implement appropriate risk reduction measures, including timely and orderly evacuation. Certain beaches in Penang have been identified as highly vulnerable to future tsunamis originating from the Andaman Sea. To determine the evacuation zones and routes, the height of the tsunami waves penetrating the beaches must be predicted in advance. However, real-time model simulations are too time-consuming for timely predictions. Therefore, in this study, an approach of applying run-up amplification factors to estimate the run-up heights is conducted to provide a simple and reliable way to obtain real-time estimation of the run-up heights. This is performed by multiplying the run-up amplification factors with the offshore incident wave heights detected or simulated by tsunami early warning system. Model simulations are performed using the in-house model TUNA-RP to obtain the run-up amplification factor and inundation distance for Penang Island. Model simulations show that the run-up amplification factors are mainly determined by the near-shore bathymetry and topography, as well as by the incoming tsunami wave heights and the incoming wave directions. The comparison between measured tsunami wave heights for the 2004 Andaman tsunami and estimated run-up heights derived from run-up amplification factors demonstrates good agreement. The estimated run-up amplification factors may be used to obtain rapid estimation of the inundation distances along the coastline of Penang Island. A comprehensive inundation map of Penang Island that could be used for rapid determination of evacuation zones is presented. The inundation distances and run-up amplification factors produced in this study would be useful to disaster and emergency managers for planning evacuation and managing coastal development.