An impact-based approach to assessing climate change’s role in changing coastal inundation risk

Mr Ben S. Hague1,2, Dr Shayne McGregor2, Dr Ruth Reef2, Dr David A. Jones1, Dr Bradley F. Murphy1

1Bureau of Meteorology, Docklands, Australia, 2School of Earth, Atmosphere and Environment, Monash University, Clayton, Australia


Recent studies have identified and projected further changes in heights of mean and extreme sea levels (e.g. 1-in-100-year return periods) due to increasing global mean sea level. However, Australia still lacks crucial information on changes to the frequency of coastal inundation impacts, and the sea levels at which these impacts occur, both vital for understanding future changes to inundation risk. This presentation will discuss a novel framework that defines coastal flood thresholds by matching reports of past flooding to tide gauge observations. Whilst the framework is generic, and will be applied nationally in subsequent work, this presentation will focus on Sydney, NSW as a case study.

By analysing exceedances of impact-based thresholds corresponding to different severities of inundation impacts, we assessed changes in coastal inundation frequency that have already occurred and the degree to which these changes can be attributed to global mean sea level rise. Through the development of coastal inundation projections under sea level rise scenarios we found regular and predictable high tides are becoming the predominant cause of impact-producing coastal inundation that will occur weekly by 2050 in Sydney. This contrasts to the historical period where similar inundation events were rarer and due to large storm surge events. This has implications for coastal risk management policy as flooding becomes chronic with continued sea level rise. Finally, by considering different emission scenarios and emergence times of regular coastal flooding, we offer insights into how this new perspective on coastal inundation risk can enhance coastal resilience and preparedness.


Ben Hague is a climatologist at the Bureau of Meteorology where he is developing datasets to monitor coastal inundation. He is also a PhD student at Monash University where his thesis topic is ‘Trends and projections of tidal inundation and extreme sea levels in Australia’.