The effect of sea-level rise on tides, extreme sea levels and waves in Port Phillip Bay in south-eastern Australia

Abstract

Long-term sea level rise (SLR) related to climate change is expected to increase coastal flood risk from extreme storm tide events in many vulnerable regions of the world by the end of the century. However, coastal inundation from these extreme events arises through the complex interaction of SLR on astronomical tides, waves, and wave-current effects. These non-linear dynamic processes were investigated for the semi-enclosed Port Phillip Bay (PPB) in south-eastern Australia using a two-way coupled hydrodynamic-wave model. The model simulated water levels due to tides, weather and waves, and aspects of wave-flow interaction over a baseline period (1980–2014) and three 20-year periods (1980–1999) using projected SLR scenarios of 0.2 m, 0.8 m, and 1.4 m (latter subsequently extended to 35 years to match baseline). The baseline simulation showed that, because of the predominant wind direction and distance from PPB Heads, the western shores of PPB were vulnerable to high Annual Exceedance Probability (AEP) water levels, but not wave heights, whereas the eastern shores experienced high AEP values for both water levels and waves. SLR simulations indicated in most regions extreme water levels within PPB would increase a further ∼10 % beyond the value of the applied SLR. Storm wave energy also increased with SLR e.g., under the 1.4 m SLR scenario, the 1 % AEP significant wave height increased by 5–10 % in most areas, and by 15–20 % in some locations near PPB Heads. These results provide important practical information for coastal management planning and policy over climate change timescales.