@article {bnh-5040, title = {Resilience to clustered disaster events at the coast: final project report}, year = {2018}, month = {11/2018}, institution = {Bushfire and Natural Hazards CRC}, abstract = {

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 Ni{\~n}a 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.

}, issn = {424}, author = {Scott Nichol} } @article {bnh-5068, title = {Improved treatment of non-stationary conditions and uncertainties in probabilistic models of storm wave climate}, journal = {Coastal Engineering}, volume = {127}, year = {2017}, month = {09-2017}, pages = {1-19}, chapter = {1}, abstract = {

A framework is presented for the probabilistic modelling of non-stationary coastal storm event sequences. Such modelling is required to integrate seasonal, climatic and long-term non-stationarities into\ coastal erosion\ hazard assessments. The framework is applied to a study site on the East Australian Coast where storm waves are found to exhibit non-stationarities related to\ El Ni{\~n}o-Southern Oscillation\ (ENSO) and seasonality. The impact of\ ENSO\ is most prominent for storm wave direction, long term mean sea level (MSL) and the rate of storms, while seasonal non-stationarity is more ubiquitous, affecting the latter variables as well as storm wave height, duration, period and surge. The probabilistic framework herein separates the modelling of ENSO and seasonal non-stationarity in the storm\ wave properties\ from the modelling of their marginal distributions, using copulas. The advantage of this separation is that non-stationarities can be straightforwardly modelled in all storm wave variables, irrespective of whether parametric or non-parametric techniques are used to model their marginal distributions. Storm wave direction and steepness are modelled with non-parametric distributions whereas storm wave height, duration and surge are modelled parametrically using extreme value mixture distributions. The advantage of the extreme value mixture distributions, compared with the standard extreme value distribution for peaks-over-threshold data (Generalized Pareto), is that the statistical threshold becomes a model parameter instead of being fixed, and so uncertainties in the threshold can be straightforwardly integrated into the analysis. Robust quantification of uncertainties in the model predictions is crucial to support hazard applications, and herein uncertainties are quantified using a novel mixture of parametric percentile bootstrap and Bayesian techniques. Percentile bootstrap confidence intervals are shown to non-conservatively underestimate uncertainties in the extremes (e.g. 1\% annual exceedance probability wave heights), both in an idealized setting and in our application. The Bayesian approach is applied to the extreme value models to remedy this shortcoming. The modelling framework is applicable to any site where multivariate storm wave properties and timings are affected by seasonal, climatic and long-term non-stationarities, and can be used to account for such non-stationarities in coastal hazard assessments.

}, doi = {https://doi.org/10.1016/j.coastaleng.2017.06.005}, url = {https://www.sciencedirect.com/science/article/pii/S0378383916302861}, author = {Davies, G and David Callaghan and Uriah Gravois and Jiang, W and David Hanslow and Scott Nichol and Tom Baldock} } @conference {bnh-3891, title = {Improving resilience to storm surge hazards}, booktitle = {AFAC17}, year = {2017}, month = {09/2017}, publisher = {Bushfire and Natural Hazards CRC}, organization = {Bushfire and Natural Hazards CRC}, address = {Sydney}, abstract = {

Winds, waves and tides associated with storms are capable of causing severe damage to coastal property and infrastructure. Locations that are prone to erosion and inundation first require an accurate assessment of risk before deciding the most cost effective mitigation option. This research aims to produce probabilistic assessments of the coastal erosion and inundation risks associated with storms, particularly for coincident or clustered events, thereby helping to strengthen the resilience of coastal communities.

Coastal erosion and inundation hazard is modelled in this study by simulations of realistic storm condition forcing (waves and tides) through a morphodynamic model to calculate return periods for maximum extent of shoreline retreat. This approach of estimating erosion return periods is superior to the assumption that the most energetic storm causes maximum erosion. The methodology is demonstrated at Old Bar, NSW, which us currently an erosion hotspot. The model will also be applied for the metropolitan Adelaide beaches. These sites were selected to test the methodology for a span of geographic conditions in terms of storm climate and deep-water wave exposure, working towards developing this method into a transportable framework applicable to other coastal areas. \ 

Desktop and field assessments of each site were conducted to document geomorphic and sediment characteristics to inform shoreline modelling. Having established the historical framework at each location, multivariate statistical analysis of wave (buoy or hindcast models) and tides for peak storm events has allowed for the synthesis of realistic future conditions. This complex sequencing of cycling between accretion and erosion incorporating cross-shore and alongshore sediment transport has been estimated using a probabilistic shoreline translation model. Here, model outputs for Old Bar are illustrated, which indicate a complex response over decadal time frames. Further work will then assess risk to infrastructure based on the most probable envelope of shoreline position. This information can then be used to inform coastal management strategies.\ 

}, author = {Uriah Gravois and Tom Baldock and David Callaghan and Davies, G and Jiang, W and Moore D and Scott Nichol} } @article {bnh-4195, title = {Resilience to clustered disaster events at the coast - storm surge: annual report 2016-17}, number = {306}, year = {2017}, month = {09/2017}, institution = {Bushfire and Natural Hazards CRC}, address = {Melbourne}, abstract = {

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 Ni{\~n}a 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 {\textendash} 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{\textquoteright}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 {\textquoteleft}hotspots{\textquoteright}. 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.


[1] Beach erosion to continue in ex-TC Debbie{\textquoteright}s wake 1 April 2017 Sunshine Coast Daily
https://www.sunshinecoastdaily.com.au/news/beach-erosion-to-continue-in-ex-tc-debbies-wake/3161769/

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 Ni{\~n}a 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 {\textendash} 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{\textquoteright}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 {\textquoteleft}hotspots{\textquoteright}. 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.


[1] Beach erosion to continue in ex-TC Debbie{\textquoteright}s wake 1 April 2017 Sunshine Coast Daily
https://www.sunshinecoastdaily.com.au/news/beach-erosion-to-continue-in-ex-tc-debbies-wake/3161769/

}, issn = {306}, author = {Scott Nichol} } @article {bnh-2918, title = {Resilience to clustered disaster events at the coast: storm surge: Annual project report 2015-2016}, number = {168}, year = {2016}, month = {08/2016}, institution = {Bushfire and Natural Hazards CRC}, address = {Melbourne}, abstract = {

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 Ni{\~n}a 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 {\textendash} 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.

Australia{\textquoteright}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. The storm event that impacted the southeast coast of Australia on the weekend of 5 May 2016 has served as a dramatic reminder of the damage that storm surge can produce, with significant beach erosion and property damage at a number of high profile locations in Sydney including Collaroy and Coogee. 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.

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 is 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\ {\textquoteleft}hotspots{\textquoteright}. 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.

}, issn = {168}, author = {Scott Nichol} } @article {bnh-2406, title = {Resilience to clustered disaster events on the coast: Storm surge}, year = {2015}, author = {Scott Nichol} } @article {bnh-2333, title = {Resilience to clustered disaster events on the coast: storm surge - Annual project report 2014-2015}, number = {122}, year = {2015}, month = {02/11/2015}, institution = {Bushfire and Natural Hazards CRC}, address = {Melbourne}, abstract = {

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 Ni{\~n}a 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. Traditional wisdom indicated that there were two storms that led to the coastal impact (May and June). However, the reanalysis data sets indicate that between January and June of 1974, there were at least 10 events but not all of these events led to coastal erorion. These prior events would have 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 {\textendash} 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{\textquoteright}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.

How are you going to solve it?

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 will focus on two case studies determined in consultation with the project end-users. Defining the hazard is non-trivial as it may be difficult to identify clustered events in the historical record. Determining the impact from a clustered event set will need to take into account the beach recovery time for the two sites. The coastal compartment framework provides the functional unit for understanding the shoreline response at a range of spatial scales, and detailed geomorphological site investigations will be undertaken and analysed within this framework for input to the beach response modelling.

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

}, issn = {122}, author = {Scott Nichol} }