Published works

What is the problem?

Coastal communities in Australia are particularly exposed to clustered disaster events, due to the impact of cyclones and extra-tropical storms when there can be coincidence of severe wind damage, storm surge, coastal flooding and shoreline erosion. Because the climatic drivers of cyclones and severe storms are stronger during or across specific years (e.g. during La Niña periods), these events often repeatedly impact the coast over periods of weeks to months. The consequences of individual events are therefore exacerbated with little or no opportunity for recovery of natural systems or communities.

The storm events that occurred on the southeast coast of Australia during 1974 are the most significant and recent in memory in terms of coastal impact associated with clustered events. The clustering in that year occurred as a series of at least 10 storms between January and June. Not all of these events led to coastal erosion, but the sequence likely played some role in setting the pre-conditions of the beach that ultimately led to the erosion towards the end of this six month period. The question therefore is to determine the beach response to clustered event sets and the nature of how those events ultimately lead to erosion.

The problem is complex as the response to the forcing will vary – there will be a spectrum from inundation to erosion, and further, there will be varying factors that drive the erosion (e.g. long-shore, cross-shore) that are functions of the location and the event.

Why it is important?

Australia’s population is concentrated along the coastline, with over 85% within 50 km of the coastline (Australian Bureau of Statistics 2001). In New South Wales for example, the NSW Government has identified 15 erosional hotspots (Kinsela and Hanslow 2013), along its 2000 km of coastline. Of the approximately 1000 km of erodible sandy beaches (open coast only), 28% is within 220 m of property. In addition to the severe wind and flooding impacts that Tropical Cyclone Debbie imparted in Queensland and New South Wales in March and April 2017, TC Debbie also caused erosion from Mackay to the Gold Coast. Any subsequent storm(s) will potentially worsen the situation at these locations, particularly if they occur before the beaches have had time to rebuild naturally. A coastal engineer at Mooloolaba (Sunshine Coast) indicated that beaches had been protected by the available large volumes of sand as the summer has been absent of the usual consistent storms[1].

How have we approached the problem?

The study will quantify the risk of these clustered events by determining the nature of the hazard, the elements that are exposed to this hazard and their resultant vulnerability. Combining the frequency of the hazard with its impact will enable the risk to be quantified. This risk can then be managed through the coastal and disaster management processes of all stakeholders.

The study has been focused on two case studies, Old Bar beach in NSW and the beaches of metropolitan Adelaide. These sites were selected in consultation with the project end-users on the basis that they are actively being managed as erosion ‘hotspots’. The physical setting of each site also presents an opportunity to advance our understanding of shoreline processes. The project has adopted the coastal compartment framework as the functional unit for understanding shoreline response at a range of spatial scales, and detailed geomorphological site investigations are being used as input to the beach response modelling.

Together, the risk and coastal compartments framework are powerful in terms of situating the assessment at local, regional and national scales.

What is the problem?

Coastal communities in Australia are particularly exposed to clustered disaster events, due to the impact of cyclones and extra-tropical storms when there can be coincidence of severe wind damage, storm surge, coastal flooding and shoreline erosion. Because the climatic drivers of cyclones and severe storms are stronger during or across specific years (e.g. during La Niña periods), these events often repeatedly impact the coast over periods of weeks to months. The consequences of individual events are therefore exacerbated with little or no opportunity for recovery of natural systems or communities.

The storm events that occurred on the southeast coast of Australia during 1974 are the most significant and recent in memory in terms of coastal impact associated with clustered events. The clustering in that year occurred as a series of at least 10 storms between January and June. Not all of these events led to coastal erosion, but the sequence likely played some role in setting the pre-conditions of the beach that ultimately led to the erosion towards the end of this six month period. The question therefore is to determine the beach response to clustered event sets and the nature of how those events ultimately lead to erosion.

The problem is complex as the response to the forcing will vary – there will be a spectrum from inundation to erosion, and further, there will be varying factors that drive the erosion (e.g. long-shore, cross-shore) that are functions of the location and the event.

Why it is important?

Australia’s population is concentrated along the coastline, with over 85% within 50 km of the coastline (Australian Bureau of Statistics 2001). In New South Wales for example, the NSW Government has identified 15 erosional hotspots (Kinsela and Hanslow 2013), along its 2000 km of coastline. Of the approximately 1000 km of erodible sandy beaches (open coast only), 28% is within 220 m of property. In addition to the severe wind and flooding impacts that Tropical Cyclone Debbie imparted in Queensland and New South Wales in March and April 2017, TC Debbie also caused erosion from Mackay to the Gold Coast. Any subsequent storm(s) will potentially worsen the situation at these locations, particularly if they occur before the beaches have had time to rebuild naturally. A coastal engineer at Mooloolaba (Sunshine Coast) indicated that beaches had been protected by the available large volumes of sand as the summer has been absent of the usual consistent storms[1].

How have we approached the problem?

The study will quantify the risk of these clustered events by determining the nature of the hazard, the elements that are exposed to this hazard and their resultant vulnerability. Combining the frequency of the hazard with its impact will enable the risk to be quantified. This risk can then be managed through the coastal and disaster management processes of all stakeholders.

The study has been focused on two case studies, Old Bar beach in NSW and the beaches of metropolitan Adelaide. These sites were selected in consultation with the project end-users on the basis that they are actively being managed as erosion ‘hotspots’. The physical setting of each site also presents an opportunity to advance our understanding of shoreline processes. The project has adopted the coastal compartment framework as the functional unit for understanding shoreline response at a range of spatial scales, and detailed geomorphological site investigations are being used as input to the beach response modelling.

Together, the risk and coastal compartments framework are powerful in terms of situating the assessment at local, regional and national scales.