Tsunami Inundation and Maritime Hazard Modelling for a Maximum Credible Tsunami Scenario in Southeast Tasmania, Australia

Abstract

The east coast of Tasmania is directly exposed to tsunamis originating from the Puysegur subduction zone, off New Zealand’s southwest coast. However, the potential impacts of tsunami inundation for coastal communities and Hobart Airport, and risks to maritime operations in Hobart Port, are poorly understood. The purpose of this project is to simulate a maximum credible earthquake/tsunami/high tide scenario (a Mw 8.7 rupture of the Puysegur subduction zone) across a 17,000 km2 model area and provide outputs that can inform local hazard management plans. Modelling was performed using the ANUGA hydrodynamic library, along with a detailed elevation model constructed from LiDAR, photogrammetric contours and bathymetric datasets. The modelling strategy comprised three primary scenarios: a 13 h simulation of tsunami activity focusing on maritime hazard from waves and currents, with two further 4 h simulations focusing on coastal inundation for 71 coastal communities and Hobart Airport. The models were run on a variable triangulated mesh with a detailed Manning’s n surface roughness model. Tsunami erosion of sand dunes was accounted for through the development of an erosion operator. Results predict severe inundation (> 4 m flow depth) in exposed east-facing areas and the maritime hazard assessment advises that water disturbance would pose a significant threat to marine craft. The assessment suggests that the feasibility of shipping evacuation from Hobart port is questionable, given the timeframes involved and the nature of simulated water disturbance. Modelling results suggest that the dune line in front of Hobart Airport would not be breached in this instance and so inundation would not occur.