Storm Surge Modelling for Bunbury Report
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Professional Opinion No. 2010/04 Storm surge modelling for Bunbury, Western Australia L. Fountain., J. Sexton, N. Habili, M. Hazelwood, and H Anderson. PREPARED FOR: Department of Planning, Western Australia and the Western Australian Planning Commission November 2010 APPLYING GEOSCIENCE TO AUSTRALIA’S MOST IMPORTANT CHALLENGES Professional Opinion 2010/04 – Storm surge modelling for Bunbury, Western Australia Professional Opinion 2010/04: Storm surge modelling for Bunbury, Western Australia November 2010 Professional Opinion 2010/04 – Storm surge modelling for Bunbury, Western Australia Department of Resources, Energy and Tourism Minister for Resources, Energy and Tourism: The Hon. Martin Ferguson, MP Secretary: Mr Drew Clarke Geoscience Australia Chief Executive Officer: Dr Chris Pigram © Commonwealth of Australia 2010 This work is for internal government use only and no part of this product may be reproduced, distributed or displayed publicly by any process without the joint permission of Geoscience Australia (GA), the Western Australian Department of Planning (DoP) and the Western Australian Planning Commission (WAPC). Requests and enquiries should be directed to the Chief Executive Officer, Geoscience Australia, GPO Box 378 Canberra ACT 2601 and the Department of Planning, Gordon Stephenson House, 140 Williams Street, Perth WA 6000. GA, DoP and WAPC and have tried to make the information in the product as accurate as possible. However, it does not guarantee that the information is totally accurate or complete. Therefore, you should not solely rely on this information when making a commercial decision. GeoCat No. 70307 Bibliographic reference: Fountain, L., Sexton, J., Habili, N., Hazelwood, M. and Anderson, H. 2010. Storm surge modelling for Bunbury, Western Australia, Professional Opinion. No.2010/04 November 2010 Professional Opinion 2010/04 – Storm surge modelling for Bunbury, Western Australia Contents 1. Executive Summary ..................................................................................................................7 2. Glossary ......................................................................................................................................9 3. Introduction .............................................................................................................................10 4. Methodology............................................................................................................................13 4.1. Storm Surge Modelling Framework............................................................................13 4.2. City of Bunbury Case Study.........................................................................................15 5. Results.......................................................................................................................................25 6. Discussion ................................................................................................................................34 6.1. Model Issues and Limitations ......................................................................................36 7. Conclusions..............................................................................................................................39 8. References ................................................................................................................................41 Appendix. A Storm scenario - background................................................................................43 Appendix. B Shoreface Translation Model (STM) Methodology - Overview ....................48 Appendix. C TC Alby observed high water levels...................................................................52 iii November 2010 Professional Opinion 2010/04 – Storm surge modelling for Bunbury, Western Australia Figures Figure 1: Storm surge modelling methodology. This project applies the GCOM2D model as developed and applied by GEMS to estimate the offshore hazard and ANUGA to estimate the storm surge inundation. The change to the coastline is estimated using the STM as developed and applied by the University of Sydney. ..........................................13 Figure 2: ‘Actual case’ (black) and ‘worst case’ (pink) tracks for TC Alby used for verification and prediction of extreme outcomes respectively..........................................17 Figure 3: Model output from GEMSURGE and the tide gauge reading at Bunbury for TC Alby............................................................................................................................................18 Figure 4: Area of interest for storm surge inundation. ...............................................................19 Figure 5: ANUGA refinement for Bunbury inundation model.................................................20 Figure 6: Synthetic gauges supplied by DoP................................................................................21 Figure 7: Sub cells within the Busselton-Rockingham coastal cell............................................23 Figure 8: Bunbury – Stratham Golf Course sub cell (#5) coastal recession risk forecast with time in the future......................................................................................................................24 Figure 9: Extent of potential recession for Bunbury by 2100. The potential costal recession distances are represented as gradated probabilities from the minimum recession of approximately 150m to the maximum extent of up to 450m. NB: the influence of the underlying geology on the extent of potential recession....................................................24 Figure 10: Maximum inundation depth (m) for Case 1 – gate open.........................................25 Figure 11: Maximum inundation depth (m) for Case 2 – gate closed.......................................26 Figure 12: Maximum inundation depth (m) for Case 2 – gate open.........................................26 Figure 13: Maximum inundation depth (m) for Case 3 – gate closed.......................................27 Figure 14: Maximum inundation depth (m) for Case 3 – gate open.........................................27 Figure 15: Maximum inundation depth (m) for Case 4 – gate closed.......................................28 Figure 16: Maximum inundation depth (m) for Case 4 – gate open.........................................28 Figure 17: Maximum inundation depth (m) for Case 5 – gate closed.......................................29 Figure 18: Maximum inundation depth (m) for Case 5 – gate open.........................................29 Figure 19: Maximum inundation depth (m) for Case 6..............................................................30 Figure 20: Time series at two of the synthetic tide gauges supplied by DoP (DoP_2 and DoP_4) for Case 5 – gate open................................................................................................31 Figure 21: Time series at two of the synthetic tide gauges supplied by DoP (DoP_2 and DoP_4) for Case 5 – gate closed. ............................................................................................32 Figure 22: Offshore synthetic tide gauges. ...................................................................................33 Figure 23: Time series at one of the synthetic offshore tide gauges (B) for Case 1. ................33 Figure 24: Time series at one of the synthetic offshore tide gauges (B) for Case 2. ................34 Figure 25: Maximum inundation depth (m) for Case 1 as modelled by GEMS......................35 Figure 26: Maximum inundation depth (m) for Case 2 as modelled by GEMS......................36 Figure 27: Elevation data coverage example................................................................................38 Figure 28: Official track of Tropical Cyclone Alby from the Bureau of Meteorology. ...........43 Figure 29: Tracks of cyclones in the Mandurah area (defined by box) for the period 1950- 2008. ...........................................................................................................................................46 Figure 30: Minimum central pressure of storms in the Mandurah area (1950-2008) – that is within box shown in Figure 29...............................................................................................46 Figure 31: Return for cyclone central pressure for the region shown in Figure 29.................47 Figure 32: Schematic diagram showing features of a tropical cyclone undergoing extra- tropical transition.....................................................................................................................47 Figure 33: Components incorporated pragmatically into morphological behaviour modelling. The objective of the STM is to enable quantitative experimentation on how 4 November 2010 Professional Opinion 2010/04 – Storm surge modelling for Bunbury, Western Australia factors in the third level influence morphological behaviour. (Source: Cowell et al., 1995)...........................................................................................................................................48 Figure 34: Responses of a sand body to sea-level rise: (a) barrier rollover where landward bypassing occurs as washover, flood-tide delta or transgressive-dune deposits; (b and c) transitional barrier truncation with a steeper backshore; (d) a mainland beach where the littoral cell is closed. (Source and further explanation: Cowell et al., 2006).............49