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Synthesis report

Synthesis report cover

Synthesis report cover

Queensland Climate Change and Community Vulnerability to Tropical Cyclones

OCEAN HAZARDS ASSESSMENT

Reporting on a joint project multi-agency investigation to assess the magnitude of the present and future ocean threat from tropical cyclones in Queensland, Australia and the vulnerability of coastal communities to extreme winds.

Synthesis Report
August 2004

An Overview and Discussion of Results from Project Stages 2,3 and 4

Executive summary

This Synthesis Report provides an overview and current summary of progress on the Queensland Climate Change and Community Vulnerability to Tropical Cyclones project. The project was instigated in 1999/2000 through the combined efforts of the Bureau of Meteorology in Queensland and the Queensland Departments of Emergency Services, Natural Resources and Mines and the Environmental Protection Agency. Financial support to date has been principally through the State Greenhouse Special Treasury Initiative (GSTI) but with increasing support from the Commonwealth/State Natural Disasters Risk Management Studies Program (NDRMSP).

The project has sought to assess:

Part A of the project has updated and extended understanding of the threat of storm tide inundation in Queensland on a state-wide scale, including the effects of extreme wave conditions in selected areas, and estimates of potential enhanced Greenhouse climate impacts. Part A represents the first major update of State-wide storm tide hazard estimates since the mid-1980s and has proceeded within the context of a Stage 1 technical blueprint setting out the essential methodologies and data requirements for a state-of-the-art assessment of the ocean hazards from tropical cyclones. Subsequent stages of the study have focused firstly on improving real-time forecasting capabilities for the Bureau of Meteorology and then on updating and extending present estimates of storm tide statistics for long-term planning and emergency response purposes and in developing near-shore extreme wave statistics for coastal management and design needs. Importantly, the potential impact of future climate change through the enhanced Greenhouse effect has also been able to be assessed within the full context of the naturally complex climatic variability of tropical cyclones. A number of the detailed recommendations from the Stage 1 blueprint have been able to be addressed, at least in part, although all components of the work have been limited by the available funding.

The project has been able to progress mainly through the application of existing numerical and statistical models having the recommended capabilities. Compared with earlier studies, the Stage 2 and 3 results indicate a reduction of estimated storm surge plus tide levels for many parts of the Queensland coast, especially North Queensland. This is consistent with the expectations of undertaking numerical modelling to a higher resolution and accuracy than achieved previously. However, the more detailed Stage 2 estimates for Hervey Bay and the Sunshine coast, which include allowance for wave setup, suggest that previously nominal allowances for this component may have been widely underestimated, thus increasing the potential impact on coastal erosion and the likelihood of inundation of some nearshore housing communities. The project has identified a critical need for further research into wave setup and that significant effort would be needed to explore this effect State-wide. The enhanced Greenhouse scenarios that have been adopted by the project are predicted to increase present climate storm tide levels by about 0.5 m on average (approximately a 19% increase), with a standard deviation of 0.13 m. The standard deviation indicates that there are regional variations and South East Queensland typically experiences higher than average predicted increases.

Within a limited budget, much progress has been made in advancing the knowledge of ocean hazards in Queensland caused by tropical cyclones, but much still remains to be done. Although sophisticated numerical and statistical models have been utilised, the data requirements are significant, much of the work is still highly labour intensive, attention to detail is critical and the coastline is extensive. The significant roadblocks to further quantification of the risks include: (i) the need to review and revise the historical database of tropical cyclone tracks, intensities and scale parameters; and (ii) obtaining high resolution land elevations to enable accurate overland flooding calculations. The project has also highlighted potential shortcomings in the present understanding of wave setup within complex topography and under extreme conditions that might only be addressed through long-term monitoring and targeted research. Finally, the relative contribution of non-cyclonic or more remote cyclonic events to medium-term return period water levels (e.g. up to 100 y) is yet to be investigated, but may be more significant than previously thought. If so, these effects may amplify enhanced Greenhouse MSL rise impacts much more than currently anticipated.

Under Part B of the project, an advanced numerical model of housing vulnerability under extreme winds has been developed for the Cairns, Townsville and Mackay regions (Stage 4). The model presently provides community-wide estimation of wind damage caused by specific cyclone scenarios and the results indicate that Cairns has a higher resilience against building damage than either of the other cities. This resilience is linked to the spatial distribution of housing age, style and the local topography. The model is also capable of being extended to other regions and enhanced to incorporate probabilistic aspects such as those resulting from the Part A outcomes. This would allow a rigorous assessment of (i) economic and societal impacts of climate change, (ii) highlight sensitivity to building styles and practices in different climatic regions, (iii) permit comparison of estimated community vulnerability with the target design resilience assumed by current building regulations, and (iv) assist in developing optimized building practices and effective long-term community insurance products. It is also identified that, in conjunction with the Part A outcomes, a similar approach could be developed to address vulnerability of housing to storm tide impacts. This issue, which is already comprehensively addressed in the USA, will increasingly be of concern for coastal communities and the tourism industry under the threat of possible sea level rise.

A number of individuals from government, consulting and academia have participated in this project over the past 4 years and their contributions are gratefully acknowledged in Appendix A.

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Last updated 16 February 2016

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