@article {bnh-7964, title = {NSW Mid North Coast flood impact research}, number = {659}, year = {2021}, month = {04/2021}, institution = {Bushfire and Natural Hazards CRC}, address = {MELBOURNE}, abstract = {

On March 18, 2021, an extreme rainfall event kicked off, resulting in severe flooding in the Mid North Coast of New South Wales. 18,000 people were evacuated, including 1,000 flood rescues. Flooding also impacted the North Coast, Hunter, Western Sydney, South Coast, Central West, and North West Regions of NSW. Flooding was also experienced in Southeast Queensland. The focus of this briefing is on flood impacts experienced on the NSW Mid North Coast.

Overview

On March 24, Risk Frontiers, with assistance from the BNHCRC, deployed a survey team to the NSW Mid North Coast region to observe and report on significant flooding in the area. Areas surveyed included, Bulahdelah, Taree, Wingham, Port Macquarie, North Haven, Laurieton, and Dunbogan. In addition to measuring flood depths and recording noteworthy damages to belongings and infrastructure, the team spoke with residents, business owners, and rescue personnel (Rural Fire Service, NSW Fire and Rescue, and State Emergency Services). Discussions covered evacuation, emergency response and communication, community resilience, and the insurability of their homes.

A couple of key issues emerged during the investigation. The first was insurance affordability in areas that were clearly at risk of flooding. Some residents and business owners we spoke with cited quotes for policies covering flood ranging from $5k - $30k per year. Our survey indicates that the full extent of damage will not be evident in claims data due to the low rates of insurance as a lot of individuals had chosen to remain uninsured due to the prohibitive costs quoted for them. Disaster mitigation needs to be considered in these areas to assist with insurance affordability.

Another common concern expressed was the lack of warning and mitigative action. For example, some residents had not considered sandbagging. Residents claimed they were either misinformed or warned too late, and then felt aspects of the process to recover were unclear.

}, keywords = {Flood, Impact, Mid North Coast, New South Wales, quick response, research}, issn = {659}, author = {Steve George and Salom{\'e} Hussein and R Crompton and Thomas Mortlock} } @article {bnh-7296, title = {Compound natural disasters in Australia: a historical analysis}, number = {605}, year = {2020}, month = {09/2020}, institution = {Bushfire and Natural Hazards CRC}, address = {Melbourne}, abstract = {

Compound disasters pose complex disaster coordination and recovery challenges. To inform disaster planning for catastrophic disasters it is essential to understand their frequency and characteristics. In this study we utilise natural disaster loss databases to identify the frequency of historical compound disasters in Australia, considering their characteristics and climate influences. Results show that compound disasters have occurred frequently and are associated with the highest seasonal losses in terms of both insured financial losses and fatalities. They may occur coincidently with other societal stressors such as wars, recessions and pandemics further exacerbating their consequences. Though their component disasters most frequently occur in eastern Australia, events can comprise disasters in both the east and west of the continent.\  There is no temporal trend in their frequency when considering financial losses, but there is a downward trend when considering only fatalities. \ It is essential that future disaster risk assessments and plans consider compound disaster scenarios. Relationships with climate drivers may assist to forecast their occurrence.

}, keywords = {compound, historical analysis, Natural disasters}, issn = {605}, author = {Andrew Gissing and Matthew Timms and Stuart Browning and Coates, Lucinda and R Crompton and John McAneney} } @article {bnh-4145, title = {A natural hazard building loss profile for Australia: 1900-2015}, number = {331}, year = {2017}, month = {10/2017}, institution = {Bushfire and Natural Hazards CRC}, address = {Melbourne}, abstract = {

This study examines building damage as recorded in PerilAUS to determine the national profile of natural peril impacts and frequencies. The analysis employs Risk Frontiers{\textquoteright} Damage Index based on a House Equivalent (HE) loss metric introduced by Blong (2003); a normalisation correction based on Crompton and McAneney (2008) and Crompton et al. (2010); and a lower bound event threshold of 25 normalised HE. The latter is equivalent to a monetary loss of around $10m in 2015-16. Normalisation puts historical events on a common footing with losses that would be incurred given 2015 societal and demographic conditions. It answers the question: what would be the building losses if historic events were to recur today?

While more validation and analysis remains to be done, we are confident that the relative importance of the various perils and their spatial distribution across states and territories has been faithfully captured. Broadly we find that there have been on average 5.85 events per year causing losses in excess of 25 normalised HE. This frequency exhibits no statistically significant change since 1900. The mean loss per event is $118m with a standard deviation of $430m.

The most costly event in terms of building damage is the 1999 Sydney hailstorm, which was also the most expensive insured loss. The losses broadly follow a Pareto distribution in which 20\% of events account for 80\% of the aggregated normalised building losses and the top 20 are responsible for 50\% of those losses. We can expect natural disaster events as costly as the 1999 Sydney hailstorm to occur about once per century, events like the Brisbane floods once every 30 to 40 years and that of the Hobart Bushfires about once a decade.

Just why most of the extreme losses {\textendash} the 1974 Brisbane floods and Cyclone Tracy in the same calendar year, the 1999 Sydney hailstorm and the 2011 Queensland and Victorian floods {\textendash} are clustered post-1970 requires further investigation. We do not believe this to be a reporting bias and know in the case of floods, for example, that Brisbane experienced much higher floods in the early and late 19th century than either the 1974 and 2011 floods. Regardless of the reason, the pattern of losses demonstrates clearly the {\textquoteleft}heavy-tailed{\textquoteright} character of the distribution of natural peril losses: in other words, there is always the possibility of event losses far in excess of the historical mean. This may be occur because of an event of higher intensity or larger footprint, that footprint impacting an area of higher-valued exposure, or all of these together.

Of all the perils, tropical cyclones have been most destructive and responsible for 30\% of the national building damage since 1900. Bushfires, floods and hail have all been similarly costly each accounting for another 18\% of building losses, although when hailstorms are combined with other storm events (excluding cyclones), thunderstorms similarly contribute 30\% of the losses. Compared with meteorological hazards, geophysical perils have had a minor influence on building damage over the last 116 years with earthquake losses dominated by a single event -- the 1989 Newcastle earthquake. However this time period is too short to predict the frequency of damaging seismic events and in the case of this peril, as with some others, the spatial pattern of losses shown here could be overturned by another extreme loss.\ 

}, issn = {331}, author = {John McAneney and Madappatt, N and Coates, Lucinda and R Crompton and Rebecca D{\textquoteright}Arcy and Blong, R} } @conference {bnh-1618, title = {Estimating the Impacts of Natural Hazards on Fatalities and Building Losses Conference Paper 2014}, booktitle = {Bushfire and Natural Hazards CRC and AFAC Wellington Conference 2014}, year = {2015}, month = {02/2015}, abstract = {

This paper is a first pass at quantifying the impacts of natural hazards on fatalities and building losses in Australia over the past century. The emphasis is on developing a methodology which allows the effects of societal changes (population and wealth) across time to be taken into consideration. This process, termed normalisation, effectively estimates the building losses or fatalities from an event as if the event were to impact present-day society, thus allowing a comparison of the most damaging natural hazard events, even if they occurred many years apart. PerilAUS, a database of natural hazard events in Australia and virtually complete since 1900, is described. Future research into losses from natural hazards in Australia is documented.

}, author = {Robin van den Honert and Coates, Lucinda and Katharine Haynes and R Crompton} } @article {bnh-3452, title = {Estimating present day extreme water level exceedance probabilities around the coastline of Australia: tropical cyclone-induced storm surges}, journal = {Climate Dynamics}, volume = {42}, year = {2014}, month = {01/2014}, pages = {139-157}, chapter = {139}, abstract = {

The incidence of major storm surges in the last decade have dramatically emphasized the immense destructive capabilities of extreme water level events, particularly when driven by severe tropical cyclones. Given this risk, it is vitally important that the exceedance probabilities of extreme water levels are accurately evaluated to inform risk-based flood and erosion management, engineering and for future land-use planning and to ensure the risk of catastrophic structural failures due to under-design or expensive wastes due to over-design are minimised. Australia has a long history of coastal flooding from tropical cyclones. Using a novel integration of two modeling techniques, this paper provides the first estimates of present day extreme water level exceedance probabilities around the whole coastline of Australia, and the first estimates that combine the influence of astronomical tides, storm surges generated by both extra-tropical and tropical cyclones, and seasonal and inter-annual variations in mean sea level. Initially, an analysis of tide gauge records has been used to assess the characteristics of tropical cyclone-induced surges around Australia. However, given the dearth (temporal and spatial) of information around much of the coastline, and therefore the inability of these gauge records to adequately describe the regional climatology, an observationally based stochastic tropical cyclone model has been developed to synthetically extend the tropical cyclone record to 10,000\ years. Wind and pressure fields derived for these synthetically generated events have then been used to drive a hydrodynamic model of the Australian continental shelf region with annual maximum water levels extracted to estimate exceedance probabilities around the coastline. To validate this methodology, selected historic storm surge events have been simulated and resultant storm surges compared with gauge records. Tropical cyclone induced exceedance probabilities have been combined with estimates derived from a 61-year water level hindcast described in a companion paper to give a single estimate of present day extreme water level probabilities around the whole coastline of Australia. Results of this work are freely available to coastal engineers, managers and researchers via a web-based tool (www.sealevelrise.info). The described methodology could be applied to other regions of the world, like the US east coast, that are subject to both extra-tropical and tropical cyclones.

}, doi = {10.1007/s00382-012-1653-0}, url = {https://link.springer.com/article/10.1007\%2Fs00382-012-1653-0}, author = {Ivan D. Haigh and Leigh R. MacPherson and M. S. Mason and E.M.S Wijeratne and Charitha Pattiaratchi and R Crompton and Steve George} } @article {bnh-3451, title = {Estimating present day extreme water level exceedance probabilities around the coastline of Australia: tides, extra-tropical storm surges and mean sea level}, journal = {Climate Dynamics}, volume = {42}, year = {2014}, month = {01/2014}, pages = {121-138}, chapter = {121}, abstract = {

The occurrence of extreme water levels along low-lying, highly populated and/or developed coastlines can lead to considerable loss of life and billions of dollars of damage to coastal infrastructure. Therefore it is vitally important that the exceedance probabilities of extreme water levels are accurately evaluated to inform risk-based flood management, engineering and future land-use planning. This ensures the risk of catastrophic structural failures due to under-design or expensive wastes due to over-design are minimised. This paper estimates for the first time present day extreme water level exceedence probabilities around the whole coastline of Australia. A high-resolution depth averaged hydrodynamic model has been configured for the Australian continental shelf region and has been forced with tidal levels from a global tidal model and meteorological fields from a global reanalysis to generate a 61-year hindcast of water levels. Output from this model has been successfully validated against measurements from 30 tide gauge sites. At each numeric coastal grid point, extreme value distributions have been fitted to the derived time series of annual maxima and the several largest water levels each year to estimate exceedence probabilities. This provides a reliable estimate of water level probabilities around southern Australia; a region mainly impacted by extra-tropical cyclones. However, as the meteorological forcing used only weakly includes the effects of tropical cyclones, extreme water level probabilities are underestimated around the western, northern and north-eastern Australian coastline. In a companion paper we build on the work presented here and more accurately include tropical cyclone-induced surges in the estimation of extreme water level. The multi-decadal hindcast generated here has been used primarily to estimate extreme water level exceedance probabilities but could be used more widely in the future for a variety of other research and practical applications.

}, doi = {10.1007/s00382-012-1652-1}, url = {https://link.springer.com/article/10.1007/s00382-012-1652-1}, author = {Ivan D. Haigh and E.M.S Wijeratne and Leigh R. MacPherson and Charitha Pattiaratchi and M. S. Mason and R Crompton and Steve George} }