Climate Change, Sea Level Rise and Coastal Subsidence along the Gippsland Coast: Implications for geomorphological features, natural values and physical assets Phase 2 - Gippsland Climate Change Study
Woodside Beach 30% 40% Existing % occurance 2070 High Level % occurance 35% 2070 Mid Level % occurance 25% 2070 High Level % difference average 30% 2070 Mid Level difference average
25% 20% 20%
15% 15% 10% % Wave field
5% 10% % Change in average Hm0 0%
-5% 5% -10%
0% -15% N NNE NE ENE E ESE SE SSE S SSW SW WSW W WNW NW NNW Wave Direction
N Calm 0.27 % Gippsland Coastal Board Final Report May 2008 Wave Height (m) Above 5 4 - 5 3 - 4 2 - 3 1 - 2 10 % Below 1
Climate Change, Sea Level Rise and Coastal Subsidence along the Gippsland Coast: Implications for geomorphological features, natural values and physical assets Phase 2 - Gippsland Climate Change Study Final Report Gippsland Coastal Board
Gippsland Coastal Board 574 Main Street, PO BOX 483 BAIRNSDALE VIC 3875 Phone: (03) 5152 0451 Fax: (03) 5152 0444 E-mail: [email protected]
Prepared for the Gippsland Coastal Board by: Eric Sjerp (Ethos NRM) Allan Charteris (Water Technology)
May, 2008
Disclaimer This report is not to be used for purposes other than that for which it was intended. The conclusions, projections and modelling used in this report are based on the best available information at the time. Where this report is to be made available, either in part or in its entirety, to a third party, Ethos NRM and Water Technology reserve the right to review the information and documentation contained herein and update findings, conclusions and recommendations as required.
ETHOS NRM WATER TECHNOLOGY ENVIRONMENTAL PLANNING & NATURAL WATER, COASTAL AND ENVIRONMENTAL CONSULTANTS RESOURCE MANAGEMENT CONSULTANTS
PO Box 204, 162 Macleod St 15 Business Park Drive Bairnsdale, Vic. 387 Notting Hill, Vic. 3168 Telephone: 03-5153 0037 Telephone: 03-9558 9366 Facsimile: 03-5153 0038 Facsimile: 03-9558 9365 E-mail: [email protected] E-mail: [email protected] Website: www.ethosnrm.com.au Website: www.watech.com.au
Specialist advice from: ENVIRONMENTAL GEOSURVEYS COASTAL GEOMORPHOLOGY SPECIALISTS
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TABLE OF CONTENTS
EXECUTIVE SUMMARY ...... 1
1 INTRODUCTION...... 8 1.1 BACKGROUND ...... 8 1.2 STUDY OBJECTIVE AND METHODOLOGY ...... 8 1.3 PREVIOUS STUDIES AND REPORTS ...... 9 1.3.1 Climate Change Impacts and Adaptation in Gippsland Project...... 11 1.4 ABOUT THE GIPPSLAND COASTAL BOARD...... 12 1.5 POLICY BASIS...... 12 2 FEATURES OF THE GIPPSLAND COAST ...... 14 2.1 NATURAL VALUES...... 14 2.2 MAJOR COASTAL TOWNS AND INFRASTRUCTURE...... 15 3 CLIMATE CHANGE AND SEA LEVEL RISE...... 17 3.1 GLOBAL CLIMATE CHANGE...... 17 3.2 CLIMATE CHANGE IN AUSTRALIA AND VICTORIA ...... 19 3.3 GLOBAL AND AUSTRALIAN SEA LEVELS...... 24 3.4 SUMMARY OF PHASE 1 GIPPSLAND CLIMATE CHANGE STUDY...... 27 3.4.1 Stage 1 Report: The effect of climate change on coastal wind and weather patterns...... 27 3.4.2 Stage 2 Report: The effect of climate change on storm surges ...... 28 3.4.3 Stage 3 Report: The effect of climate change on extreme sea levels in Corner Inlet and the Gippsland Lakes ...... 30 4 COASTAL SUBSIDENCE...... 32
5 COASTAL GEOLOGY, EROSION POTENTIAL AND SEDIMENT TRANSPORT ..36 5.1 COASTAL GEOLOGY AND EROSION POTENTIAL ...... 36 5.2 SEA LEVEL RISE AND COASTAL EROSION...... 38 5.3 WAVE MODELLING AND SEDIMENT TRANSPORT...... 42 6 POTENTIAL IMPACTS AND THREATS TO THE GIPPSLAND COAST...... 46 6.1 OVERVIEW OF POTENTIAL IMPACTS ...... 46 6.2 SAN REMO TO WILSON’S PROMONTORY...... 48 6.2.1 Coastal Erosion Potential ...... 48 6.2.2 Coastal Erosion Threats - Environmental ...... 48 6.2.3 Coastal Erosion Threats - Cultural...... 49 6.2.4 Coastal Erosion Threats – Infrastructure...... 49 6.2.5 Vulnerable Sites ...... 49 6.3 CORNER INLET AND NOORAMUNGA COAST...... 51 6.3.1 Coastal Erosion Potential ...... 51 6.3.2 Coastal Erosion Threats - Environmental ...... 51 6.3.3 Coastal Erosion Threats - Cultural...... 52 6.3.4 Coastal Erosion Threats – Infrastructure...... 52 6.3.5 Vulnerable Sites ...... 52 6.4 NINETY MILE BEACH AND GIPPSLAND LAKES...... 54 6.4.1 Coastal Erosion Potential ...... 54 6.4.2 Coastal Erosion Threats - Environmental ...... 54
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6.4.3 Coastal Erosion Threats - Cultural...... 55 6.4.4 Coastal Erosion Threats – Infrastructure...... 55 6.4.5 Vulnerable Sites ...... 55 6.5 LAKES TYERS TO NSW BORDER ...... 59 6.5.1 Coastal Erosion Potential ...... 59 6.5.2 Coastal Erosion Threats - Environmental ...... 59 6.5.3 Coastal Erosion Threats - Cultural...... 59 6.5.4 Coastal Erosion Threats – Infrastructure...... 59 6.5.5 Vulnerable Sites ...... 59 7 ADAPTIVE MANAGEMENT FOR SEA LEVEL RISE AND CLIMATE CHANGE ALONG THE GIPPSLAND COAST...... 62 7.1 ADAPTIVE MANAGEMENT...... 62 7.2 PRO-ACTIVE RESPONSE TO CLIMATE CHANGE THREATS ...... 62 7.2.1 Awareness Raising...... 62 7.2.2 Future Planning...... 63 7.3 RE-ACTIVE RESPONSE TO CLIMATE CHANGE THREATS ...... 64 7.3.1 Do Nothing ...... 64 7.3.2 Planned Retreat ...... 65 7.3.3 Adaptation...... 65 7.3.4 Protection...... 66 7.4 RISK MANAGEMENT ...... 67 8 RECOMMENDATIONS FOR FUTURE WORK ...... 69 8.1 IMPROVED CLIMATE CHANGE AND SEA LEVEL RISE MODELS ...... 69 8.2 GEOLOGICAL SURVEY...... 69 8.3 DETAILED TOPOGRAPHIC / TERRAIN DATA...... 69 8.4 INUNDATION DUE TO COASTAL SUBSIDENCE...... 70 8.5 ACTION FOR LOCAL GOVERNMENT...... 70 8.6 REGIONAL STAKEHOLDERS ...... 71 9 CONCLUSION...... 72
10 REFERENCES ...... 75
11 MAPS ...... 78 11.1 COASTAL GEOLOGY...... 78 11.2 COASTAL EROSION POTENTIAL...... 78 11.3 COASTAL VALUES AND THREATS - ENVIRONMENTAL ...... 78 11.4 COASTAL VALUES AND THREATS - INFRASTRUCTURE...... 78 11.5 COASTAL VALUES AND THREATS – CULTURAL ...... 78 12 APPENDICES...... 84 12.1 CLIMATE CHANGE WAVE MODELLING ...... 84
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TABLES Table 3-1 Summary of relevant IPCC Fourth Assessment Report conclusions (IPCC, 2007a) ...... 18 Table 3-2 Projected change in climate for Victoria by 2030, relative to 1990. (Source: Hennessy et al., 2006)...... 21 Table 3-3 Summary of projected climate changes for West Gippsland (Source: DSE, 2004a) Note: Based on earlier CSIRO climate models...... 22 Table 3-4 Summary of projected climate changes for East Gippsland (Source: DSE, 2004b) Note: Based on earlier CSIRO climate models...... 23 Table 3-5: Summary of various sea level rise projections...... 26 Table 3-6 100 year return levels for storm surge heights at selected locations along the coast under current climate and 2030 and 2070 scenarios. (Source: McInnes et al., 2005b) ...... 29 Table 3-7 100 year return levels for the combination of storm tide height and mean sea level rise at selected locations along the coast under current climate and 2030 and 2070 scenarios (Source: McInnes et al., 2005b)...... 29 Table 3-8 Storm tide return levels for selected locations around Corner Inlet under current climate and 2030 and 2070 low, mid and high scenarios including corresponding mean sea level rise scenarios (Source: McInnes et al., 2005c) ...... 30 Table 3-9 Storm tide return levels for selected locations around the Gippsland Lakes under current climate and 2030 and 2070 low, mid and high scenarios including corresponding mean sea level rise scenarios (Source: McInnes et al., 2005c)...... 31 Table 4-1 Maximum predicted subsidence at Golden Beach (between Rosedale and Darriman Fault Systems) for 2031 and 2056, using realistic and pessimistic scenarios. (Source: Freij-Ayoub et al., 2007)...... 33 Table 5-1 Proportion of each geological type along the Gippsland coast...... 37 Table 5-2 Shoreline erosion/recession based on Bruun Rule for various sea level rise scenarios...... 40 Table 5-3: Summary of sediment transport analysis for existing conditions versus 2070 climate change estimates ...... 43
FIGURES Figure 3-1 Observed changes in (a) global average surface temperature; (b) global average sea level rise from tide gauge (blue) and satellite (red) data and (c) Northern Hemisphere snow cover for March-April. All changes are relative to corresponding averages for the period 1961-1990. Smoothed curves represent decadal averaged values while circles show yearly values. (Source: IPCC, 2007) ...... 20 Figure 3-2 Annual Mean Australian Temperature Anomalies (from 30yr 1961- 1990 average ) for 1910 to 2005 (Source: CSIRO & Bureau of Meteorology (2007) ...... 21 Figure 3-3 IPCC Third Assessment Report (TAR) projections of global average sea level rise from 1990 to 2100, for six different emissions scenarios. (IPCC, 2001, Source: Pittock, 2003) ...... 25
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Figure 3-4 Synoptic weather conditions responsible for storm surges of at least 0.4 m at Lakes Entrance (Source: McInnes et al., 2005b) ...... 28 Figure 5-1 Proportion of Gippsland Coast threatened by High, Moderate and Low erosion risk...... 38 Figure 5-2 Top: Effect of Storm waves on sandy beach profile Bottom: Bruun Rule beach profile response to sea level rise (after Swartz, 1967)...... 39 Figure 5-3: Potential breach of barrier dunes along Ninety Mile Beach based on ocean storm tide and lake flooding for three scenarios (From: Ethos NRM and Water Technology, 2008...... 41 Figure 5-4: Sediment Transport – Existing versus 2070 climate change estimates ...... 44 Figure 6-1 Flood inundation at Lakes Entrance for 0.0m AHD (top), 1.0m AHD (middle), and 2.0m AHD (bottom) (Source: Wheeler, P., 2008)...... 58
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EXECUTIVE SUMMARY The Gippsland coast is home to thousands of people who live in or near one of the many coastal towns and settlements located between San Remo on the eastern extent of Western Port Bay and Mallacoota near the NSW Border. Despite these built up areas, the Gippsland coast remains in a largely natural state, being characterised by diverse natural and cultural values, including important habitat for a range of fauna species protected by National Parks, Reserves and public foreshore land. Climate change, sea level rise and coastal subsidence all have the very real potential to significantly impact on the Gippsland coast, affecting both natural values and built infrastructure, on private and public land. Physical assets associated with townships and potentially at risk range from isolated boat ramps and jetties to valuable private properties fronting prime foreshore land. Phase 2 Gippsland Climate Change Study This report presents the findings for Phase 2 of the Gippsland Climate Change Study. The study assesses the coastal geological characteristics and the erosion potential of the Gippsland coast, and based on existing climate change predictions, also determines the likely changes to coastal sediment transport patterns along the coast. Potential impacts of climate change-induced sea level rise to physical assets and natural values along the coast have been identified. Strategies to protect, relocate or adapt to these threatened assets are discussed. Key Coastal towns and settlements Key towns and settlements occurring within the Gippsland coast study area are illustrated on maps at the rear of this report and include (from west to east) : San Remo Port Albert Seaspray The Barrier Kilcunda Tarraville Seacombe Lakes Entrance Inverloch Robertson Beach Hollands Landing Lake Tyers Venus Bay Manns Beach Loch Sport Marlo Walkerville McLoughlins Beach Banksia Peninsula Bemm River Waratah Bay Honeysuckles Ocean Grange Tamboon South Sandy Point Gomar Beach Eagle Point Tamboon Port Franklin Paradise Beach Paynesville Gypsy Point Toora Sth (Grip Rd) Golden Beach Bairnsdale Mallacoota Port Welshpool Woodside Beach Metung A number of these towns are located inland on estuarine water bodies. Climate Change Little doubt now remains that global climates are changing. The Intergovernmental Panel on Climate Change (IPCC), CSIRO, the Bureau of Meteorology and others have demonstrated the extent to which global warming will change climatic conditions and cause sea level rise, at a global and local scale.
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IPCC Fourth Assessment Report Conclusions (IPCC, 2007a) · There is unequivocal observational evidence of; - global warming (11 of last 12 years were among the warmest years on record), - increased ocean temperatures, - widespread melting of snow & retreating of sea-ice and glaciers, - widespread changes in precipitation amounts, - changes in wind patterns, - changes in extreme weather, including droughts, and - rising global sea levels over the 20th century of ~ 0.17m. · Global average surface temperatures are projected to increase by between 1.1°C and 6.4°C by the end of the 21st century. · Global average sea level is projected to rise; 0.18m to 0.38m (Low emission scenario) 0.26m to 0.59m (High emission scenario) higher than present by the end of the 21st century. · Additional 0.1m to 0.2m sea level rise if break-up of polar ice sheets accelerates. · Climate change will adversely affect water resources, agriculture, forestry, fisheries, ecological systems, human settlements and human health in many parts of the world. · Global warming and sea level rise will continue for centuries due to timescale lags associated with climate processes, even if greenhouse gas emissions were stabilised. Phase 1 of the Gippsland Climate Change Study (McInnes et al., 2005a & b, 2006) and earlier work by CSIRO indicates that the major impacts of Climate change to weather systems along the Gippsland coast include: Phase 1 Gippsland Climate Change Study (McInnes et al., 2005a & b, 2006) · Increase dominance of south-westerly frontal synoptic weather patterns · Increase wind speed · Increased storm surge height - up to 19% by 2070 · Increased frequency and intensity of extreme events by approx. 10%. Bigger storms … more often Summaries of projected climate changes for both West Gippsland and East Gippsland (Table 3-3 and Table 3-4) have been produced by the Department of Sustainability and Environment (2004a&b), based on CSIRO climate models. Sea Level Rise Large fluctuations in sea level are a natural occurrence over geologic timeframes, primarily influenced by global climate change associated with glacial and inter-glacial episodes. Smaller scale fluctuations have occurred during the Holocene (last ~10,000 years). However, sea level rise resulting from present-day climate change is a consequence of two main processes; thermal expansion of the oceans as surface waters increase in temperature, and melting of land-based ice sheets and glaciers which contribute additional water to oceans, thereby increasing water levels (CSIRO & Bureau of Meteorology, 2007).
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A summary of projected sea level rise scenarios from various previous/existing studies is presented below. Projected Sea Level Rise - Gippsland Coast · IPCC, 2007a: Global range = 0.18m to 0.59m by end of the 21st century with additional 0.1m to 0.2+m for accelerated ice sheet melt (= up to 0.79m) · CSIRO/DSE, 2004: Gippsland range = 0.07m to 0.55m by 2070 · CSIRO/McInnes et al., 2006: Gippsland range = up to 0.49m by 2070 (for high emissions and high wind strength increase scenario) · Rahmstorf, 2007: Global sea level rise in excess of 1.0m by 2100 (based on continued temperature increase and melting of polar ice sheets) · West Gippsland Catchment Management Authority: Gippsland range = 0.49m by 2070 (interim policy position based on CSIRO data) · Victorian Coastal Council (2007): Victorian range = 0.4m to 0.8m by end of the 21st century (Draft policy position based on high emissions scenario and increased melting of polar ice sheets)
(note differing time scales) Based on IPCC projections and further work by Rahmstorf (2007), Hansen (2007) and CSIRO & Bureau of Meteorology (2007), the Victorian Coastal Council’s Draft Victorian Coastal Strategy (VCC, 2007) adopts, as policy for planning purposes along the entire Victorian coast, a projected sea level rise of 0.4m to 0.8m above present sea level by the end of this century. The Garnaut Climate Change Review prepared for the Australian Government (Garnaut, 2008) highlights that global temperature, CO2 emissions and sea level rise observations are all trending towards the upper limits of existing projections, hence emphasising the need to adopt a precautionary approach and consider the upper limit of current sea level rise projections as the most likely scenario. Coastal Geology and Erosion Potential Assessment of coastal geology along the Gippsland coast, undertaken as part of this study, indicates that: Key Conclusions: Geology and Erosion Potential · Highly erodible sediments (Coastal Dunes {including sandy beaches}, Colluvium, Alluvium) comprise approximately 78% of the Gippsland Coast. · Moderately erodible areas (Sandstone, Limestone, Sedimentary) comprise about 13% of the coast. This includes sedimentary areas such as the Croajingalong coast that may have a Low erodibility. · Low erodibility areas (Granite and Volcanic) make up approximately 9% of the coast, generally around Wilsons Promontory and other rocky headlands such as Cape Conran. · Importantly, approximately 65% (1,233km) of the Gippsland coast comprises Coastal Dune Systems. These areas are typically low-lying, comprising unconsolidated sediments and hence are highly susceptible to erosion. Sea Level Rise and Coastal Erosion Highly erodible sections of the Gippsland coast, as identified above, will be most at risk from the effects of climate change-induced sea level rise and increased storm surges. As sea level rises, erodible shorelines (dunes, sand, alluvium, colluvium) will retreat as beach slope and dune profiles adjust to altered (raised) water levels. The Bruun Rule provides a simplistic estimate of likely costal erosion due to sea level rise - for every
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10cm of sea level rise, shoreline recession of 5-10m can be expected, depending on local wave conditions and sand dune characteristics. Detailed modelling of Ninety Mile Beach (Ethos NRM and Water Technology, 2008) indicates that sea level rise and concurrent flooding in the Gippsland Lakes couldresult in a breach of the coastal barrier dunes. Key Conclusions: Sea Level Rise and Coastal Erosion · Highly erodible sections of the Gippsland coast (dunes, sand, alluvium, colluvium) will be most at risk from the effects of climate change-induced sea level rise and increased storm surges. · A 0.79m sea level rise by year 2100 (based on the IPCC high emission scenario of 0.59m plus up to approx 0.2m for continued ice sheet melt), will result in as much as 40m to 79m erosion/retreat along Gippsland’s sandy coast (using simplistic Bruun Rule calculations). · Modelling of Ninety Mile Beach (Ethos NRM and Water Technology, 2008) indicates that a 1 in 100 year storm under a 0.8m yr 2100 sea level rise scenario coinciding with flooding in Lake Reeve could result in several breaches of the barrier dunes protecting Lake Reeve. Wave Modelling and Sediment Transport Detailed wave and sediment transport modelling undertaken as part of this study (Appendix 1) indicates that, due to climate change-induced increased wind speeds and up to 10% increase in wave heights, there will be significant changes to existing coastal sediment transport regimes along the Gippsland coast. Key Conclusions: Sediment Transport · Climate change-induced increased wind strength (based on IPCC high and medium emissions scenarios for 2070) will change wave conditions in Bass Strait, leading to changed sediment transport patterns along the Gippsland coast. · Numeric modelling for a 2070 high emissions scenario (Water Technology, 2007) predicts locations west of Wilsons Promontory will experience:
An increase in gross sediment transport resulting in increased seasonal variability to beach and dune profiles, and
Reduced net westward sediment transport (except Sandy Point) · Locations East of Wilsons Promontory are predicted to experience:
Significant increase in gross sediment transport resulting in increased seasonal variability to beach and dune profiles, and
Significant increase in eastward sediment transport, resulting in possible erosion at the western end of beach cells and deposition towards the east. Subsidence Land subsidence ranging from centimetres to several metres has been recorded in a diverse range of environments including Venice in Italy, Bangkok in Thailand, San Joaquin Valley in California, USA and in the Latrobe Valley, Gippsland. Potential land subsidence along the Gippsland coast is caused by fluid (oil, gas and water) extraction form the Latrobe Aquifer. Findings of recent studies by CSIRO and the Department of Primary Industries have been summarised as part of this study and shown below.
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Key Conclusions: Coastal Subsidence (From Freij-Ayoub et al. (2007): · Coastal land subsidence is predicted to occur to differing degrees along almost the entire Ninety Mile Beach. · Greatest subsidence is predicted in an area centred on the coast at Golden Beach. · Maximum subsidence under a ‘realistic’ scenario is predicted to be 0.51m by 2031 and 0.48m by 2056. · Maximum subsidence under a ‘pessimistic’ scenario is predicted to be 0.87m by 2031 and 1.2m by 2056. · Any land subsidence along the Gippsland coast will exacerbate the effect of sea level rise and future coastal erosion. · Inundation maps for the combined effect of land subsidence and increased storm tide and wave heights due to climate change predict that under both the ‘realistic’ and ‘pessimistic’ scenarios, the majority of coastal dunes between Seaspray and Rotamah Island are almost entirely inundated. · Significant uncertainties and limitations remain for the data used to generate coast subsidence and inundation predictions along the Gippsland coast. · To date, high resolution ground surveys have not detected any statistically valid land subsidence (other than at the Latrobe Valley open pit coal mines) (AAMHatch, 2006, 2007) Potential Impacts and Threats to the Gippsland coast Coastal erosion, flooding and large scale changes to Gippsland’s coastline caused by climate change not only has the potential to impact on a very broad range of environmental and cultural values, but may also pose a direct threat to an array of physical assets along the Gippsland coast. The most vulnerable coastal sites are low- lying areas and/or those that have a high potential for erosion, and hence shoreline retreat. Section 6 of this report presents a detailed assessment of environmental and cultural values and infrastructure assets that are potentially at risk. A summary is presented below. The most dramatic potential impact will result from the erosion and breaching of coastal dunes and barrier islands that currently protect inlets, estuaries, low-lying plains and wetlands located immediately behind the dunes and barrier islands. Once eroded, and if the breach is sustained (remains open), the lack of these protective barrier dunes will result in rapid inundation by sea water, increased marine influence, and ultimately creating coastal embayments subject to greater tidal variation, increased wave action and potentially substantially increased erosion and flooding (Ethos NRM, 2008). A sustained breach in a barrier dune complex is most likely to occur following several large storm events, in rapid succession, such that the eroded beach/dunes/islands do not have an opportunity to reform.
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Overview: Potential impacts to the Gippsland coast from sea level rise, increased coastal erosion and changed coastal processes Environmental Impacts · Increased flooding of low-lying areas · Increased inundation from storm surge effect · Increased saline water (tidal) intrusion into estuaries, rivers and coastal embayments · Accelerated coastal erosion due to higher mean water levels and increased storm intensity · Changed beach and dune morphology due to increased erosion and changed sediment transport patterns · Large scale modification to coastal landforms, particularly river deltas and breaching of coastal barrier dunes protecting inlets and estuaries such as the Gippsland Lakes · Potential erosion and loss of barrier dune islands protecting Corner Inlet · Increased wave penetration into ‘breached’ estuaries · Altered inundation frequencies for fringing estuarine wetlands · Ecological collapse of systems unable to tolerate increased marine environment, particularly wetlands and fringing estuarine/riparian vegetation · Modified distribution of fauna species, particularly estuarine-dependent fish and birds · Increased erosion threat to jetties, sea walls, canals, roads, bridges etc · Flooding and loss of efficiency of stormwater drainage systems · Potential loss of Crown land frontage along private coastal land Infrastructure at Potentially at Risk · Private residences, including canal estates · Commercial shops and service industries · Roads and bridges, including highways · Utilities, including power, telecommunications, water mains, sewer mains and associated pump stations, and reticulated gas · Stormwater and drainage · Beach groynes · Port facilities, including ramps, jetties, breakwaters, navigation aids · Public boat ramps · Private jetties · Septic tanks · Recreational foreshore areas comprising walking tracks, picnic sites and related public facilities · Surf life saving facilities and clubrooms · Threat (including perceived threat) to property values · Altered recreational opportunities along coastal zone.
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Response to Climate Change and Sea Level Rise Response to climate change and sea level rise needs to be both pro-active, comprising increasing community awareness and planning for change, and re-active responses which involve either: · Doing nothing, · Retreating from impacted areas, · Adapting to (or accommodating) the change, or · Protecting (or defending) an area against the impact of the change. Many physical assets along the Gippsland coast can most likely be adequately and cost- effectively protected against the impacts of sea level rise, at least in the short to medium term. However, on a larger and far more complex scale, entire communities and dwellings may need to be relocated because the cost of protecting such areas from erosion and/or flooding is prohibitively high, particularly when on-going maintenance of protective measures is included. Some low-lying dwellings and coastal communities along the Gippsland coast may ultimately find that a managed relocation by retreating to higher ground is the only cost-effective long term response option. On-going protection measures such as dykes, levee banks, sea walls and pumps could be effective in the short term but would require considerable maintenance/replacement and upgrading over time. A vital component of adequate risk management involves being able to make balanced decisions regarding the most appropriate action, based on the magnitude of the risk, its consequences, the cost of taking action and the preparedness of the community to both pay for action and ‘forego private rights’. The key step towards being able to make informed and consistent decisions is for Government to provide clear policy direction regarding anticipated climate change and sea level rise impacts through proclaiming a statutory sea level rise and/or erosion setback, depicted as an overlay or development control in municipal planning schemes. Local Government will therefore need considerable support from State and Commonwealth Government to enable adequate planning and risk management tools to be incorporated into decision making frameworks.
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1 INTRODUCTION
1.1 Background Sea level rise and altered weather patterns due to global climate change, and possible coastal land subsidence due to oil, gas and water extraction, have the potential to cause significant impacts along the Gippsland coast. The Gippsland Coastal Board is conducting a two-phase Gippsland Climate Change Study to better understand the range of possible impacts to assist in the future development of appropriate tools to manage risks and enable effective adaptive responses by Government, local stakeholders and individuals. Phase 1 of the study was completed by CSIRO, resulting in the release of three separate reports (McInnes et al., 2005a & b, 2006) that quantify possible changed coastal wind and weather patterns, changed storm surge conditions and changes in extreme sea levels along the Gippsland coast due to projected climate change scenarios. This report forms Phase 2 of the Gippsland Climate Change Study. It uses the knowledge gained during Phase 1 to model the potential impact to the Gippsland coast’s geomorphological features and processes, to its natural values, and to built assets such as roads, bridges, jetties and water/sewerage/power services in low-lying township areas. Phase 2 of the study will also provide information to assist coastal managers in their long-term decision making and strategic planning. The need to better understand the potential impacts of climate change and sea level rise was highlighted by the release in 2007 of the Intergovernmental Panel on Climate Change Fourth Assessment Report (IPCC, 2007a & b). In an Australian context, the recent Garnaut Climate Change Review (Garnaut, 2008) prepared for the Australian Government further reinforces the need to assess potential impacts at a regional and local scale. Along the Gippsland coast, the dual effect of projected sea level rise and potential coastal land subsidence will cause increased flooding and have a potentially catastrophic impact upon natural resources, physical processes, infrastructure and physical assets of built up areas, and upon recreational opportunities experienced along the coast.
1.2 Study Objective and Methodology The objective of this Phase 2 - Gippsland Climate Change Study is to determine the implications of sea level change and coastal subsidence based on the various scenarios outlined in the three CSIRO reports (McInnes et al., 2005a & b, 2006). Specifically the study seeks to: 1) Determine the likely impacts, and identify the risk profile, of: · Gross changes to coastal processes and geomorphology along the Gippsland coast (including coastal embayments and estuarine systems), such as breaching of barrier dune systems (ie Gippsland Lakes), shoreline erosion/deposition, and erosion of offshore sandy islands (dissected barrier formations).
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· Shoreline inundation/flooding along the Gippsland coast, taking into account the increased effect of tides and storm surge on water bodies (estuarine lagoons, and embayments) that may have previously been protected by coastal dunes or offshore islands. · Increased water/sea level and changed coastal processes on the natural and physical assets of both public and private land along the Gippsland coast. 2) Identify and recommend appropriate approaches and tools to assist decision- making, to better manage risks and to enable effective adaptive responses. Study Area The study area extends along the Gippsland coast from San Remo in the west to the NSW border, east of Mallacoota. Methodology In additional to existing information from CSIRO, the Intergovernmental Panel on Climate Change and numerous other sources, this report has been prepared based on new work, undertaken by the authors, comprising an assessment of the Gippsland coast’s erodibility, detailed wave and sediment transport modelling (Appendix 1), a threats analysis, and on stakeholder input. No new modelling of coastal land subsidence was undertaken as part of this study, rather the findings of recent studies by CSIRO and the Department of Primary Industries are used to better understand the dual effects of sea level rise and potential land subsidence along the Gippsland coast. A Discussion Paper (Water Technology & Ethos NRM, 2007) was prepared and distributed to a range of stakeholder groups (Government agencies, coastal land managers and community groups). It formed the basis for several workshops at which feedback was sought on an initial threats analysis and local knowledge of participants was recorded using annotated aerial photography of the Gippsland coast. The identification in this report of coastal features that are potentially at risk from climate change, sea level rise and coastal subsidence is based on the authors’ local knowledge, input from workshop participants, input from stakeholders, and informed by information presented in a variety of previous studies.
1.3 Previous Studies and Reports A variety of reports have previously been prepared that relate to or inform the process of identifying potential impacts of climate change, sea level rise and coastal subsidence along the Gippsland coast. Relevant reports are listed below, a number of which are describe in greater detail in subsequent chapters of this report. Global climate change impacts have been reported on in detail by the Intergovernmental Panel on Climate Change (IPCC, 2001, 2007a & b). A summary is provided in Section 3.1. CSIRO have, as Phase 1 of the Gippsland Climate Change Study, completed three detailed investigations into Climate Change in Eastern Victoria: · Stage 1 Report: The effect of climate change on coastal wind and weather patterns (McInnes et al., 2005a)
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· Stage 2 Report: The effect of climate change on storm surges (McInnes et al., 2005b) · Stage 3 Report: The effect of climate change on extreme sea levels in Corner Inlet and the Gippsland Lakes (McInnes et al., 2006) Results from the Phase 1 Gippsland Climate Change Study reports by CSIRO are summarised in Sections 3.4 and are available on the Gippsland Coastal Board website at www.gcb.vic.gov.au CSIRO have also previously prepared reports on Climate Change in Victoria: High Resolution Assessment of Climate Change Impacts (Whetton et al., 2002), and information for a number of regional climate change booklets, including for West Gippsland and East Gippsland (DSE, 2004a & b). Further reports on sea-level rise around the Australian coastline and the changing frequency of extreme sea-level events have been prepared by Church et al. (2006a & b). CSIRO and the Bureau of Meteorology (2007) have produced a comprehensive technical summary of all climate change science relevant to Australia. The recent Garnaut Climate Change Review prepared for the Australian Government (Garnaut, 2008) highlights that global temperature, CO2 emissions and sea level rise observations are all trending towards the upper limits of existing projections, hence emphasising the need to adopt the upper limit of current sea level rise projections. West Gippsland Catchment Management Authority auspiced A Regional Pilot Project Initiating Gippsland’s Response to Climate Change, details of which are discussed in section 1.3.1. The Gippsland Coastal Board, in establishing the scope of the current investigation, has previously prepared an overview of potential climate change impacts to the Gippsland coast (Sjerp, 2002). Riedel and Sjerp (2007) demonstrated the long term erosional nature of Ninety Mile Beach using historic aerial photography and inspection of coastal landforms. A detailed investigation using a high resolution (LiDAR) digital elevation model of Ninety Mile Beach between Honeysuckles and Paradise Beach) (Ethos NRM and Water Technology, 2008) demonstrated the extent of potential inundation/flooding, due to sea level rise, of low-lying private land located behind narrow coastal barrier dunes within Wellington Shire. The study also identified locations where the coastal barrier dunes could potentially be breached as a result of sea level rise and subsequent coastal erosion. Results from the investigation are being used to determine future options for development of private land along Ninety Mile Beach. The implications of a sustained breach, due to sea level rise and coastal erosion, in barrier dunes forming the Gippsland Lakes was summarised for a workshop investigating the potential impacts of climate change on the Gippsland Lakes (Ethos NRM, 2008). Findings of the investigation also apply to other coastal barrier lagoon- style estuaries along the Gippsland coast. Flooding extent at Lakes Entrance has been modelled using survey data and Geographic Information System (GIS) interactive web-based visualisation tools by Wheeler (2008). Highly accurate topographic information (LiDAR) is currently being collected by the Department of Sustainability and Environment (and supported by the Gippsland Coastal Board) to enable construction of a digital elevation model for the entire Victorian coast.
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This information, when available, will allow accurate assessment of potential flooding and inundation using different sea level rise projections. A case study of the St Kilda foreshore in the City of Port Phillip, Melbourne (NATCLIM, 2007), provides a climate change risk assessment to assist with future planning for climate change in the City of Port Phillip. Older studies of the impacts of climate change include investigations into coastal vulnerability undertaken by the Port of Melbourne Authority (PMA, 1992) and Lawson & Treloar Pty Ltd (1996). The Australian Greenhouse Office has published two risk management guidelines relating to climate change in Australia: Climate Change Impacts and Risk Assessment (AGO, 2006a), which targets business and Government, describes a detailed risk assessment process, whilst Climate Change Scenarios for Initial Assessment of Risk in Accordance with Risk Assessment Guidance (AGO, 1006b) was written by CSIRO and provides a summary of various climate change scenarios and the predicted range of impacts for ten regions throughout Australia. Falling water levels in the Latrobe Aquifer and possible causal relationships to land subsidence along the Gippsland coast have been investigated by CSIRO (Hatton et al., 2004; Underschultz et al., 2006; Freij-Ayoub et al., 2007), following earlier work by Sinclair Knight Merz (SKM, 1995 & 2000). Speakers notes from subsidence seminars held by the Gippsland Coastal Board in April 2000 have also been compiled (GCB, 2000). Findings by Freij-Ayoub et al. (2007) are summarised in Section 4. The Department of Primary Industries (DPI) is undertaking a series of highly accurate ground elevation measurements in the Gippsland Basin region to reliably identify if land subsidence is taking place. Surveys have been completed for the period June 2004 to 2007 (AAMHatch, 2004, 2006 & 2007). 1.3.1 Climate Change Impacts and Adaptation in Gippsland Project In 2005 West Gippsland Catchment Management Authority auspiced A Regional Pilot Project Initiating Gippsland’s Response to Climate Change, with a final report - Climate Change Impacts and Adaptation in Gippsland (Fisher, 2006) that includes a record and outcomes from several workshops and stakeholder consultations. Of particular value is the report’s Appendix 1, which was prepared by CSIRO (Brooke and Hennessy, 2005) and describes climate change impacts in Gippsland, elaborating on the CSIRO reports discussed in sections 3.4. The report also contains a very useful climate change directory for Gippsland. Workshops and stakeholder consultations undertaken as part of the project identified general climate change impacts, information needs and gaps, and prioritised actions based on a number of themes, including Water, Rivers and Coasts. Key relevant coastal-related findings included: · Wetlands, estuaries, coastal dune stability and coastal urban infrastructure are some of the most vulnerable ‘areas and activities of concern’ · Altered environmental flows, and potential loss of sites of high biodiversity value were also identified. · Impacts were thought to result mainly from sea level rise, increased storm surge, flooding, inundation, increased extreme weather events, coastal erosion, and loss of protective dunes.
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· Strategic land use planning was seen as a key management tool. · Some coastal towns were seen as being ‘unsustainable’ in the longer term. Many other issues and potential impacts were identified but not necessarily relevant to the current study which focuses on potential coastal impacts. Key relevant coastal-related recommendations were: · To continue research and accurate forecasting of potential climate change and sea level rise impacts to the Gippsland coast. · To obtain additional information regarding impacts to infrastructure resulting from increased storm surge, sea level rise and flooding. · To develop contingency scenarios. · To review planning controls in Gippsland to ensure they reflect potential impacts of climate change, particularly flooding. Results and copies of project reports, including appendices and workshop presentations are available on the West Gippsland Catchment Management Authority website at www.wgcma.vic.gov.au.
1.4 About the Gippsland Coastal Board The Gippsland Coastal Board is one of three regional Coastal Boards formed under the Coastal Management Act 1995. The Gippsland Coastal Board reports to the Minister for Environment & Climate Change and to the Victorian Coastal Council, the statewide umbrella organisation. The Gippsland Coastal Board’s principal role is to implement the Victorian Coastal Strategy (VCC, 2002) through providing advice to the Minister and the Victorian Coastal Council, through the development of Coastal Action Plans (CAP) and by facilitating improved coastal management through liaison with industry, government and the community. The Board has completed a number of Coastal Action Plans including; Gippsland Lakes Coastal Action Plan (1999), Gippsland Boating Coastal Action Plan (2002), Integrated Coastal Planning for Gippsland Coastal Action Plan (2002), and the Gippsland Estuaries Coastal Action Plan (2006). The Board has also produced numerous detailed management guidelines and information brochures to encourage improved coastal management outcomes. The Board works co-operatively with other organisations to initiate and implement specific projects consistent with actions identified in Coastal Action Plans. Strategic and action planning, rather than on-ground works, together with community education form the Board’s main activities.
1.5 Policy Basis Gaining a better understanding of how vulnerable the Gippsland coast is to the effects of climate change is supported by a broad range of a policy objectives outlined in the following key documents: • Victorian Greenhouse Strategy (DSE, 2002 & 2005 update) • Adapting to Climate Change: Enhancing Victoria's Capacity (DSE, 2004c)
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• Our Environment, Our Future - Sustainability Action Statement 2006 (DSE, 2006) • Victorian Coastal Strategy (VCC, 2002) • Draft Victorian Coastal Strategy (VCC, 2007) • East Gippsland & West Gippsland Regional Catchment Strategies (EGCMA, 2006; WGCMA, 2005) • Municipal planning schemes prepared by local Councils • Integrated Coastal Planning for Gippsland - Coastal Action Plan (GCB, 2002) • Gippsland Lakes Coastal Action Plan (GCB, 1999) • Numerous management plans prepared by Parks Victoria for Coastal, Marine and National parks along the Gippsland coast. • Coastal Spaces Final Recommendations (DSE & VCC, 2006). • Coastal Urban Design Frameworks prepared by local Councils for numerous coastal settlements along the Gippsland coast. • Numerous foreshore management plans/strategies prepared by the Department of Sustainability and Environment, local municipalities and/or Committees of Management for foreshore areas fringing coastal estuaries along the Gippsland coast.
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2 FEATURES OF THE GIPPSLAND COAST
2.1 Natural Values The Gippsland coast contains a range of important natural features potentially at risk from climate change, sea level rise, changes to coastal processes, and coastal land subsidence. In summary these features include: · Diverse natural, cultural and landscape values · National, Marine & Coastal Parks · Areas recognised internationally for: o Biological significance & diversity o Ramsar wetlands o Migratory bird habitat (JAMBA & CAMBA) · Numerous Victorian BioSites / sites of flora or fauna significance / threatened species · Broad range of Ecological Vegetation Classes (EVC’s), some poorly represented and/or unique to Gippsland · Numerous sites of Aboriginal cultural significance · Diverse range of significant geomorphological values including: o Long sandy beaches with complex nearshore sediment transport budgets o Large coastal dunes, including barrier dune complexes backed by estuarine lagoons o Rocky headlands and wave cut platforms o Estuaries, lakes and wetlands o River mouths and deltas o Hinterland comprising undulating foothills and low-lying coastal plains. Dominant landscape features along the Gippsland coast include: · Bunurong Coast · Anderson Inlet · Cape Liptrap · Shallow Inlet · Wilsons Promontory · Corner Inlet and coastal rivers & streams · Ninety Mile Beach and barrier dunes · Jack Smith Lake · Gippsland Lakes and Lake Tyers · Lower Snowy River Wetlands · Sydenham and Tamboon Inlets · Cape Howe · Small estuaries, rivers, sandy beaches and high dunes of Far East Gippsland · Croajingolong coast and Mallacoota Inlet. Threats to these natural and cultural values are considered in section 6, including maps illustrating the distribution of each feature (at rear).
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2.2 Major Coastal Towns and Infrastructure Physical infrastructure located at and between townships along the Gippsland coast varies considerably. Large areas, particularly within National/Coastal Parks and Crown Land reserves, remain undeveloped and are devoid of any substantial built infrastructure or assets other than relatively isolated boat ramps and access paths. Likewise, a significant proportion of private land along the coast and fringing estuaries and embayments is undeveloped. Where physical infrastructure does exist, it often relates to or is associated with a built- up coastal township or settlement. It is these assets, which occur on both public and private land, that are potentially at risk from climate change, sea level rise, changed coastal processes and coastal subsidence. The key towns and settlements occurring within the study area along the Gippsland coast are illustrated on maps at the rear of this report and include :
San Remo Manns Beach Eagle Point Kilcunda McLoughlins Beach Paynesville Inverloch Honeysuckles Bairnsdale Venus Bay Gomar Beach Metung Walkerville Paradise Beach The Barrier Waratah Bay Golden Beach Lakes Entrance Sandy Point Woodside Beach Lake Tyers Port Franklin Seaspray Marlo Toora Sth (Grip Rd) Seacombe Bemm River Port Welshpool Hollands Landing Tamboon South Port Albert Loch Sport Tamboon Tarraville Banksia Peninsula Gypsy Point Robertson Beach Ocean Grange Mallacoota
A number of these towns are located inland on estuarine water bodies and would become threatened only if existing coastal barrier dunes were breached. The range of coastal infrastructure associated with these communities includes: · Private residences, including canal estates · Commercial shops and service industries · Roads and bridges, including highways · Utilities, including power, water mains, sewer mains and associated pump stations, and reticulated gas · Stormwater and drainage · Beach groynes · Port facilities, including ramps, jetties, breakwaters, navigation aids · Public boat ramps · Private jetties
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· Septic tanks · Recreational foreshore areas comprising walking tracks, picnic sites and related public facilities · Surf life saving facilities and clubrooms A consolidated inventory of physical infrastructure along the Gippsland Coast does not exist, however municipal councils, VicRoads, Gippsland Ports and utility companies have records of their assets, including; roads, drainage, buildings (ie kiosks, surf clubs etc), power, telephone, water, sewage, jetties and wharfs. The economic value of infrastructure along the Gippsland coast, and more importantly, the value of that potentially at risk from sea level rise and coastal subsidence, is difficult to determine. Rating databases could provide private land and building values, whilst the depreciated replacement value often attributed to an asset by its owner (ie council or utility company) could provide a value for drains, roads and buildings. No attempt has been made in this study to determine the precise location of physical infrastructure along the Gippsland Coast, nor its economic value.
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3 CLIMATE CHANGE AND SEA LEVEL RISE
3.1 Global Climate Change Little doubt now remains that global climates are changing. It is, however, important to distinguish between ‘natural’ variability in weather patterns caused by phenomena such as El Nino (Southern Oscillation) - which causes extended periods of below average rainfall in south eastern Australia on a semi-cyclic basis - and climate change resulting from human-induced changes to atmospheric concentrations of greenhouse gases. The drought experienced in Gippsland over recent years was more closely related to a mild El Nino event (BoM, 2007) than a direct manifestation of global climate change, although it may to a small extent be exacerbated by an ‘overprint’ of changed global climatic conditions. The Intergovernmental Panel on Climate Change (IPCC) was established in 1988 by the United Nations' Environment Program and the World Meteorological Organisation. It is responsible for providing the international community with authoritative advice on scientific, technical and economic issues relating to climate change. IPCC's Third Assessment Report (TAR) (IPCC, 2001) concluded that global warming had accelerated in recent decades. The recently released Fourth Assessment Report (4AR) Climate Change 2007: The Physical Science Basis – Summary for Policy Makers (IPCC, 2007a) and Climate Change Impacts, Adaptation and Vulnerability (IPCC, 2007b) increases the level of scientific certainty upon which climate change and projections are made and provides stronger evidence that the majority of global surface warming is attributable to increases in greenhouse gas emissions associated with human activities. Table 3-1 summarises the IPCC Fourth Assessment Report (IPCC, 2007a) in the context of the present investigation along the Gippsland coast.
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Table 3-1 Summary of relevant IPCC Fourth Assessment Report conclusions (IPCC, 2007a) IPCC Fourth Assessment Report Conclusions (IPCC, 2007a) · There is unequivocal observational evidence of;
- global warming (11 of the last 12 years were among the warmest years on record), - increased ocean temperatures, - widespread melting of snow & retreating of sea-ice and glaciers, - widespread changes in precipitation amounts, - changes in wind patterns, - changes in extreme weather, including droughts, and - rising global sea levels over the 20th century of ~ 0.17m. · Global average surface temperatures are projected to increase by between 1.1°C and 6.4°C by the end of the 21st century. · Global average sea level is projected to rise; 0.18m to 0.38m (Low emission scenario) 0.26m to 0.59m (High emission scenario) higher than present by the end of the 21st century. · Additional 0.1m to 0.2m sea level rise if break-up of polar ice sheets accelerates. · Climate change will adversely affect water resources, agriculture, forestry, fisheries, ecological systems, human settlements and human health in many parts of the world. · Global warming and sea level rise will continue for centuries due to timescale lags associated with climate processes, even if greenhouse gas emissions were stabilised.
The IPCC 4th report (IPCC, 2007a) makes the following key conclusions which are illustrated in Figure 3-1.
· Warming of the climate system is unequivocal, as is now evident from observations of increases in global average air and ocean temperatures, widespread melting of snow and ice, and rising global average sea level. · Global atmospheric concentrations of carbon dioxide, methane and nitrous oxide have increased markedly as a result of human activities since 1750 and now far exceed pre-industrial values determined from ice cores spanning many thousands of years. · At continental, regional, and ocean basin scales, numerous long-term changes in climate have been observed. These include changes in Arctic temperatures and ice, widespread changes in precipitation amounts, ocean salinity, wind patterns and aspects of extreme weather including droughts, heavy precipitation, heat waves and the intensity of tropical cyclones. · Most of the observed increase in globally averaged temperatures since the mid-20th century is very likely [as apposed to likely, TAR, 2001] due to the observed increase in anthropogenic greenhouse gas concentrations. · Eleven of the last twelve years (1995 -2006) rank among the 12 warmest years in the instrumental record of global surface temperature (since 1850). The total temperature increase from 1850 – 1899 to 2001 – 2005 is 0.76 °C.
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The linear warming trend over the last 50 years of 0.13 °C per decade is nearly twice that for the last 100 years. · For the next two decades a warming of about 0.2°C per decade is projected for a range of emission scenarios. [Model-based projections of global average surface warming at the end of the 21st century (2090-2099), range from:] 1.1°C – 2.9°C higher than present [Low emission scenario] to 2.4°C – 6.4°C higher than present [High emission scenario] · Global average sea level rose at an average rate of 1.8 mm per year over 1961 to 2003. There is high confidence that the rate of observed sea level rise increased from the 19th to the 20th century. The total 20th century rise is estimated to be 0.17m. · Model-based projections of global average sea level rise at the end of the 21st century (2090-2099) …… [range from] ….. 0.18m – 0.38m higher than present [Low emission scenario] to 0.26m – 0.59m higher than present [High emission scenario] · Anthropogenic warming and sea level rise would continue for centuries due to the timescales associated with climate processes and feedbacks, even if greenhouse gas concentrations were to be stabilized.
3.2 Climate Change in Australia and Victoria Climate change observations throughout Australia are summarised by CSIRO & Bureau of Meteorology (2007), and Hennessy et al. (2006, citing numerous authors): · From 1910 to 2004, the Australian-average maximum temperature rose 0.6°C and the minimum temperature rose 1.2°C. · 2005 was the Australian continent’s warmest year since 1910. · The north-western two-thirds of Australia has become wetter since 1950, while southern and eastern Australia has become drier. Droughts have become hotter and therefore more intense. · From 1950 to 2005, extreme daily rainfall has increased in north-western and central Australia and over the NSW western tablelands, but decreased in the southeast, southwest and central east-coast. Annual Mean Australian Temperature Anomalies are illustrated in Figure 3-2. Projected climate changes for Victoria, based on CSIRO climate models, are shown in Table 3-2. Summaries produced by the Department of Sustainability and Environment in 2004 of projected climate changes for both West Gippsland and East Gippsland are provided in Table 3-3 and Table 3-4 respectively, although the information is based on earlier CSIRO climate models.
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Figure 3-1 Observed changes in (a) global average surface temperature; (b) global average sea level rise from tide gauge (blue) and satellite (red) data and (c) Northern Hemisphere snow cover for March-April. All changes are relative to corresponding averages for the period 1961-1990. Smoothed curves represent decadal averaged values while circles show yearly values. (Source: IPCC, 2007)
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Figure 3-2 Annual Mean Australian Temperature Anomalies (from 30yr 1961- 1990 average ) for 1910 to 2005 (Source: CSIRO & Bureau of Meteorology (2007)
Table 3-2 Projected change in climate for Victoria by 2030, relative to 1990. (Source: Hennessy et al., 2006)
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Table 3-3 Summary of projected climate changes for West Gippsland (Source: DSE, 2004a) Note: Based on earlier CSIRO climate models.
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Table 3-4 Summary of projected climate changes for East Gippsland (Source: DSE, 2004b) Note: Based on earlier CSIRO climate models.
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3.3 Global and Australian Sea Levels Large fluctuations in sea level are a natural occurrence over geologic timeframes, primarily influenced by global climate change associated with glacial and inter-glacial episodes. Smaller scale fluctuations have occurred during the Holocene (last ~10,000 years). The Victorian coastline experienced a period of slightly higher than present sea level between 4000 and 6000 years ago, followed by a relatively stable mean sea level for the past 4000 years (Bird, 1993). Recent observational records indicate that global sea levels have risen an average of 1.8 mm per year between 1961 and 2003, and that the rate has increased to 3.1mm per year between 1993 and 2003 (IPCC, 2007a,b). Church and White (2006) demonstrated that global sea levels rose by approximately 0.17m during the 20th century. This rate of sea level rise, caused by global warming, is more rapid than that caused by ‘natural’ long term (geological time scale) sea level change associated with glacial and inter- glacial episodes, and smaller scale fluctuations that have occurred during the Holocene. In Victoria, monitoring stations established at Lorne and Stony Point as part of the Australian Baseline Sea Level Monitoring Project have recorded short-term rises of 2.8mm per year and 2.4mm per year respectively since monitoring commenced in 1993 (BOM, 2006). The IPCC Third Assessment Report (TAR) projected global sea level would rise between 0.05m to 0.32m by 2050, and between 0.09m to 0.88m centimetres by 2100, depending on various emissions scenarios (IPCC, 2001). Refer Figure 3-3. Climate change, or more specifically global warming, causes sea level rise by two main The IPCC Fourth Assessment Report processes: (IPCC, 2007a) further refined these · thermal expansion of the oceans as projections, indicating that global sea level surface waters increase in temperature, and will rise between 0.18m to 0.59m by the · melting of land-based ice sheets and end of the 21st century (0.18m to 0.38m glaciers which contribute additional water for low emissions scenario, or 0.26m to to oceans, thereby increasing water levels. 0.59m for high emissions scenario). Variations in the amount of sea level rise Accelerated melting of the Greenland and around the globe are due to the influence of Antarctic ice sheets are predicted to ocean currents and spatial variations in the increase the upper ranges of projected amount of ocean warming. sea level rise by a further 0.1m to 0.2m (CSIRO & Bureau of Meteorology, 2007) (IPCC, 2007a).
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Global average sea level rise 1990 to 2100 for the SRES scenarios. Each of the six lines appearing in the key is the average of AOGCMs for one of the six illustrative scenarios. The region in dark shading shows the range of the average of AOGCMs for all thirty five SRES scenarios. The region in light shading shows the range of all AOGCMs for all thirty five scenarios. The region delimited by the outermost lines shows the range of all AOGCMs and scenarios including uncertainty in land-ice changes, permafrost changes and sediment deposition. Note that this range does not allow for uncertainty relating to ice-dynamic changes in the West Antarctic ice sheet. (After IPCC, Third Assessment Report - Climate Change 2001)
Figure 3-3 IPCC Third Assessment Report (TAR) projections of global average sea level rise from 1990 to 2100, for six different emissions scenarios. (IPCC, 2001, Source: Pittock, 2003)
The IPCC Fourth Assessment Report (2007a) is, by virtue of its consensus nature, a relatively conservative projection of anticipated global sea level rise. Several researchers (Rahmstorf, 2007; Hansen, 2007; and CSIRO & Bureau of Meteorology, 2007) have Global sea level is projected by the highlighted that sea level rise is likely to be even IPCC to be 18-59cm by 2100, with a greater - in excess of 1.0m by yr 2100 - than that possible additional contribution from projected by the IPCC because of recent ice sheets of 10 to 20cm. However, further ice sheet contributions that observational trends (primarily continued high can not be quantified at this time greenhouse gas emissions and accelerating may increase the upper limit of sea melting of polar ice sheets), and due to further level rise substantially. Global ‘positive feedback’ resulting from increasing climate models indicate that mean ocean temperatures preventing seasonal sea level rise on the east coast of Australia may be greater than the reforming of polar ice sheets, with the resultant global mean sea level rise. loss of solar reflection further heating ocean waters. (CSIRO & Bureau of Meteorology, 2007)
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Studies by CSIRO as part of the Gippsland Climate Change Study (McInnes et al., 2005a & b, 2006) have provided detailed analysis for south eastern Australia (refer to Section 3.4 for details). In summary, these studies found that, at worst, the Gippsland coast is likely to experience increased wind speed, increase dominance of southwesterly frontal synoptic weather patterns, increased storm surge, increased storm tide heights, and increased frequency and intensity of extreme events. In the worst-case predicted wind speed scenario, storm tide height would increase by up to 0.20m by 2070, and sea level will rise up to 0.49m by 2070 (for a high emissions scenario). In the absence of a definitive state-wide policy position on projected sea level rise, the West Gippsland Catchment Management Authority has adopted 0.49m rise by 2070 as an interim policy position based on CSIRO data (Wayne Gilmore, WGCMA, pers. comm.). Based on IPCC projections and the further work by Rahmstorf (2007), Hansen (2007) and CSIRO & Bureau of Meteorology (2007), the Victorian Coastal Council’s Draft Victorian Coastal Strategy (VCC, 2007) adopts as policy for planning purposes along the entire Victorian coast, a projected sea level rise of 0.4m to 0.8m above present sea level by the end of this century. The Garnaut Climate Change Review prepared for the Australian Government (Garnaut, 2008) highlights that global temperature, CO2 emissions and sea level rise observations are all trending towards the upper limits of existing projections, hence emphasising the need to adopt a precautionary approach and consider the upper limit of current sea level rise projections as the most likely scenario.
Table 3-5: Summary of various sea level rise projections Projected Sea Level Rise - Gippsland Coast · IPCC, 2007a: Global range = 0.18m to 0.59m by end of the 21st century with additional 0.1m to 0.2+m for accelerated ice sheet melt · CSIRO/DSE, 2004: Gippsland range = 0.07m to 0.55m by 2070 · CSIRO/McInnes et al., 2006: Gippsland range = up to 0.49m by 2070 (for high emissions and high wind strength increase scenario) · Rahmstorf, 2007: Global sea level rise in excess of 1.0m by 2100 (based on continued temperature increase and melting of polar ice sheets) · West Gippsland Catchment Management Authority: Gippsland range = 0.49m by 2070 (interim policy position based on CSIRO data) · Victorian Coastal Council (2007): Victorian range = 0.4m to 0.8m by end of the 21st century (Draft policy position based on high emissions scenario and increased melting of polar ice sheets)
(note differing time scales)
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3.4 Summary of Phase 1 Gippsland Climate Change Study CSIRO (McInnes et al., 2005a & b, 2006) completed Phase 1 of Gippsland Climate Change Study, which investigated three aspects relating to the extent and impact of sea level rise and subsidence along the Gippsland coast: Stage 1 focused on changes to future coastal wind and weather patterns, then applying this understanding, and the predictions of sea level rise and subsidence, to storm surge and storm tide hazards - Stage 2. Stage 3 involved applying this same methodology to determine extreme Phase 1 of the Gippsland Climate Change sea levels inside the embayments of the Study (McInnes et al., 2005a & b, 2006) and earlier work by CSIRO indicates that the Gippsland Lakes and Corner Inlet. major impacts of Climate Change to Phase 1 of the Gippsland Climate Change weather systems along the Gippsland Study (McInnes et al., 2005a & b, 2006) and coast include: earlier work by CSIRO concludes that the • Increase dominance of south-westerly frontal synoptic weather patterns major impacts of Climate Change to weather systems along the Gippsland coast • Increase wind speed include an increase dominance of south- • Increased storm surge height - up to 19% by 2070 westerly frontal synoptic weather patterns, an increase wind speed, an increased storm • Increased frequency and intensity of extreme events by approx. 10% Bigger surge height - up to 19% by 2070, and an storms … more often increased frequency and intensity of extreme events by approx. 10%. The summaries below are abridged text taken from the respective reports. 3.4.1 Stage 1 Report: The effect of climate change on coastal wind and weather patterns Storm surges along the eastern Victorian coastline are caused by severe winds and, to a lesser degree, the associated falling atmospheric pressure that accompanies them. McInnes et al. (2005a) used climate model simulations to analyse the nature of synoptic events responsible for storm surges along the eastern Victorian coast and the projections of future changes in their relative frequencies and associated wind speeds. Results of the investigation formed the basis of the Stage 2 and 3 investigations. Six synoptic weather systems in Bass Strait and the southern Tasman Sea that are responsible for severe winds and elevated sea level conditions along the eastern Victorian coast were identified: prefrontal, frontal, post-frontal, Tasman low, cut-off low and continental low. Each system has different wind directions and speeds. The three stages of frontal events were the most frequently occurring patterns, accounting for 69% of severe wind days. Based on thirteen climate model simulations, future changes in mean wind speeds were found to have strong seasonality with a tendency towards increases over southeastern Victoria, Bass Strait and the southern Tasman Sea in winter and spring, weak increases in summer and decreases in autumn, although the models contained a large degree of uncertainty. Analysis of tide gauge data with the tidal component removed yielded residuals that provide information about the influence of weather on sea levels. A daily maximum sea level residual value of 0.4m or greater was used as a threshold for storm surge identification. Approximately 96% of elevated storm surge events at Stony Point were due to the passage of cold fronts while only 1% was due to Tasman lows. Elevated sea
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Page 27 Climate Change, Sea Level Rise and Coastal Subsidence along the Gippsland Coast: Implications for geomorphological features, natural values and physical assets Phase 2 - Gippsland Climate Change Study Final Report Gippsland Coastal Board levels at Lakes Entrance were caused by fronts in about 71% of occasions, Tasman lows in about 23% of cases and cut-off lows in about 3% of cases. Using CSIRO’s climate models, the number of frontal days contributing to the most severe 1% of wind days both increased and decreased slightly (depending on the model) for the 2030 and 2070 scenarios, when compared to a 1961 to 1990 reference period. 3.4.2 Stage 2 Report: The effect of climate change on storm surges Hydrodynamical modelling and statistical analysis of extreme sea level events were used to determine the effect of climate change on storm surges by developing spatial patterns of storm surge recurrence intervals under present climate conditions and those projected to occur in 2030 and 2070 (McInnes et al., 2005b). Storm surges along the south coast occur year round, however, storm surges are more common in the winter months, when more severe cold fronts traverse the southern coastline, and the largest increases projected for wind speed occur in winter. Since this could point to a shift to more frequent storms during winter, a ‘worstcase’ scenario with winter changes was also analysed. Investigation of the meteorological drivers of storm surges indicated that at Lakes Entrance 70% of storm surges of at least 0.4 m were due to cold fronts while 23% were due to Tasman lows and 6% were due to east coast lows (Figure 3-4). Cold fronts elevate sea levels along a larger portion of the eastern Victorian coastline while the effect of Tasman lows was confined to the coastline east of Wilsons Promontory
Figure 3-4 Synoptic weather conditions responsible for storm surges of at least 0.4 m at Lakes Entrance (Source: McInnes et al., 2005b)
Generally, the projected increases in storm surge heights are small owing to the relatively small magnitude storm surges that occur along the Gippsland coast. The high values for annual average wind speed changes for 2030 and 2070 result in approximate increases in storm surge height of 6 and 19% respectively. Projected 100 year return levels for storm surge heights are shown in Table 3-6. The combination of storm surge and prevailing tide provides the total sea level. The highest storm surges along the eastern Victorian coast occur from Lakes Entrance eastwards, the highest tides occur to the west of Wilsons Promontory. The highest storm tides also occur in this region. Mean sea level rise will have a larger impact on sea level extremes over eastern Victoria than wind speed-induced changes (ie. storm tide height) in the future. The 2030 mid and 2070 mid storm tide changes are about 12 to 15 % of the respective mean sea level rise scenarios. Changes in sea level resulting from the combination of both wind speed
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Page 28 Climate Change, Sea Level Rise and Coastal Subsidence along the Gippsland Coast: Implications for geomorphological features, natural values and physical assets Phase 2 - Gippsland Climate Change Study Final Report Gippsland Coastal Board changes (ie. storm tide height) and mean sea level rise are summarised in Table 3-7 for the 1 in 100 year event.
Table 3-6 100 year return levels for storm surge heights at selected locations along the coast under current climate and 2030 and 2070 scenarios. (Source: McInnes et al., 2005b)
Table 3-7 100 year return levels for the combination of storm tide height and mean sea level rise at selected locations along the coast under current climate and 2030 and 2070 scenarios (Source: McInnes et al., 2005b)
Other climate change variables that are likely to impact on coastal vulnerability include extreme rainfall events that can accompany southern Tasman lows and east coast lows - which are responsible for about 30% of storm surge events that occur at Lakes Entrance. Rainfall from these systems is likely to increase under climate change and so flood risk within Lakes Entrance due to the combination of extreme sea levels and runoff would be expected to increase also. Projected wind speed changes will also impact on the wave heights experienced during extreme storm surge events, which could influence coastal erosion.
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3.4.3 Stage 3 Report: The effect of climate change on extreme sea levels in Corner Inlet and the Gippsland Lakes Results of the Stage 1 and 2 investigations were used to determine the impact of climate change on sea level heights and inundation around Corner Inlet and the Gippsland Lakes (McInnes et al., 2006). The sea level heights due to the combination of the storm tides with the corresponding mean sea level rise scenario are presented in Table 3-8 for several locations around Corner Inlet. The inundation resulting from sea level extremes is greatest across the islands and northern coastline of the inlet. The inundation in the regions of the towns of Port Franklin, Port Welshpool and Port Albert will increase by between 15% and 30% by 2070 under a high wind speed change, high mean sea level rise scenario.
Table 3-8 Storm tide return levels for selected locations around Corner Inlet under current climate and 2030 and 2070 low, mid and high scenarios including corresponding mean sea level rise scenarios (Source: McInnes et al., 2005c)
Elevated sea levels along the open coastline adjacent to the Gippsland Lakes are most commonly caused by the southwesterlies that accompany the passage of cold fronts. These produce 1 in 100 year sea levels of approximately 0.71 m on the open coastline. The narrow entrance to the Gippsland Lakes significantly limits the flow of water from Bass Strait. Furthermore wind setup means that the highest sea levels are in the northeast of the Lakes and so there is no height differential across the entrance to induce such flow. The sea level heights due to the combination of the storm tides with the corresponding mean sea level rise scenario are presented in Table 3-9 for several locations around the Gippsland Lakes. The inundation resulting from sea level extremes will be greatest in existing swamp areas and in the vicinity of Lake Reeve, located along the barrier between the Lakes and the open coastline. The total area of inundation within the model domain doubles from current climate values of around 25 km2 to just over 50 km2 under a 2030 high wind speed change, high mean sea level rise scenario. It increases by a further 25% relative to 2030 under the corresponding scenario for 2070.
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Table 3-9 Storm tide return levels for selected locations around the Gippsland Lakes under current climate and 2030 and 2070 low, mid and high scenarios including corresponding mean sea level rise scenarios (Source: McInnes et al., 2005c)
These storm tide and mean sea level rise projections for locations within the Gippsland Lakes are in addition to increased water levels caused by flood waters emanating from the Gippsland Lakes catchment.
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4 COASTAL SUBSIDENCE Land subsidence ranging from centimetres to several metres has been recorded in a diverse range of environments including Venice in Italy, Bangkok in Thailand, San Joaquin Valley in California, USA and in the Latrobe Valley, Gippsland. Land subsidence occurs as a result of either: a) tectonic movements involving a net lowering of the land surface over long time periods (hundreds to thousands of years), or from b) the extraction of underground water, oil and/or natural gas resulting in a relatively rapid collapse (compaction) of underlying strata and hence a lowering of the land surface – such as is the case surrounding the Latrobe Valley open pit coal mines where ground water from the Latrobe Aquifer is extracted for dewatering purposes. The extent of subsidence is a function of the amount of fluid extracted, the geological characteristics of the aquifer from which fluid is extracted and overlying strata, the distribution of geological faults, and the rate of aquifer recharge (both natural and artificial). Remedial actions to reduce land subsidence include a cessation of fluid extraction and/or artificial recharge to the aquifer. This report summarises the findings of recent studies by CSIRO and the Department of Primary Industries into potential land subsidence along the Gippsland coast caused by fluid extraction form the Latrobe Aquifer. A Risk Analysis for Subsidence in the Gippsland Coast (SKM, 1995) identified that extraction of irrigation groundwater (5000-10,000 ML/yr), mine dewatering (25,000- 30,000 ML/yr) and offshore oil and gas production (100,000 ML/yr) were the principle cause of a major lowering in the Latrobe Aquifer. Analysis of data from 12 groundwater monitoring bores indicated a reduction in groundwater of between 10 to 40 metres. The risk analysis predicted subsidence ranging from millimetres if remedial actions were implemented immediately, up to approximately 2 metres in approximately 70 years time if no action is taken. Further studies commissioned by the Minerals and Petroleum Division of the Department of Natural Resources and Environment (SKM 2001a & b), modelled the possible range of subsidence near Golden Beach and near Yarram in South Gippsland and concluded that the risk of subsidence along the Gippsland coast was considerably less than originally predicted. However, the reports also highlighted that further geotechnical sampling was required to obtain more reliable and confident estimates of subsidence. A Ground Elevation Project being undertaken in South Gippsland for the Department of Primary Industries - Minerals and Petroleum Division has re-established a network of highly accurate monitoring benchmarks, monitoring of which ceased approximately ten years ago. The network comprises 3 reference stations in stable ground (connected directly to bedrock) and 14 monitoring stations located in ground potentially subject to subsidence along the 100km coastal strip between Port Albert and Loch Sport. Results from monitoring surveys completed for the period June 2004 to May 2007 (Epochs 1, 2 & 3) have not detected any statistically valid land subsidence (other than at the Latrobe Valley open pit coal mines) (AAMHatch, 2006, 2007). The lack to-date of (statistically valid) detectable land subsidence along the Gippsland coast may in part be due to the lag interval between extraction from the aquifer and
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Page 32 Climate Change, Sea Level Rise and Coastal Subsidence along the Gippsland Coast: Implications for geomorphological features, natural values and physical assets Phase 2 - Gippsland Climate Change Study Final Report Gippsland Coastal Board commencement of subsidence. This lag is in part dependent on the geological characteristics of the aquifer and the overlying strata, which remain poorly understood. Using the earlier subsidence modelling work by SKM, the survey monitoring data by AAMHatch, previous CSIRO subsidence investigations (Hatton et al., 2004: Underschultz et al., 2006) and climate change modelling (McInnes et al., 2005a & b, 2006), CSIRO have recently completed a detailed simulation of coastal subsidence and storm wave inundation risk in the Gippsland Basin (Freij-Ayoub et al., 2007). The simulation model uses two scenarios – a ‘realistic’ prediction and a ‘pessimistic’ prediction of subsidence, each for two time periods – by year 2031 and by 2056. Modelling predictions are based on lithological data and well head pressures from numerous wells along the Gippsland coast. The study area extends from west of McLoughlins Beach to Bunga Arm near Sperm Whale Head (West of Lakes Entrance), and is divided into three ‘regions’ based on the discrete geological fault systems. Results presented by Freij-Ayoub et al. (2007) demonstrate that coastal subsidence is predicted to occur to differing degrees across almost the entire study area, with the greatest subsidence predicted in an area centred on the coast at Golden Beach (between the Rosedale Fault System and Darriman Fault System, and where the Latrobe aquifer is the thickest). The report presents a series of subsidence contour maps that illustrate the range in predicted subsidence levels. By 2031 the realistic scenario predicts a maximum subsidence of 0.51m and a pessimistic scenario maximum subsidence of 0.87m. For 2056, the realistic scenario predicts a maximum subsidence of 0.48m and a pessimistic scenario maximum subsidence of 1.2m. Table 4.1. summarises the findings.
Table 4-1 Maximum predicted subsidence at Golden Beach (between Rosedale and Darriman Fault Systems) for 2031 and 2056, using realistic and pessimistic scenarios. (Source: Freij-Ayoub et al., 2007) Time Period Maximum Predicted Realistic Maximum Predicted Pessimistic Subsidence Scenario Subsidence Scenario 2031 0.51m 0.87m Max Range = 0.22m to 0.51m Max Range = 0.30m to 0.87m 2056 0.48m 1.20m Max Range = 0.20m to 0.48m Max Range = 0.47m to 1.20m
Inundation maps prepared by Freij-Ayoub et al. (2007) illustrate the extent of flooding that would likely result from lowering of coastal areas due to land subsidence. Additional maps illustrate the likely inundation that would result from the combined effects of coastal land subsidence and the increased storm tide and wave heights predicted due to climate change (based on McInnes et al., 2005a & b, 2006). Areas affected by subsidence alone are restricted to relatively small areas surrounding the margins of Lake Reeve, whereas areas affected by inundation resulting from increased storm tide and wave heights are more extensive. The contribution to overall (combined) inundation from subsidence was found to be significantly less than that contributed by inundation resulting from increased storm tide and wave heights (Freij- Ayoub et al., 2007). The combined subsidence and climate change inundation maps, for both 2031 & 2056 and for both the realistic and pessimistic scenarios, show that the majority of the outer
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Page 33 Climate Change, Sea Level Rise and Coastal Subsidence along the Gippsland Coast: Implications for geomorphological features, natural values and physical assets Phase 2 - Gippsland Climate Change Study Final Report Gippsland Coastal Board dunes between Seaspray and Rotamah Island are almost entirely inundated. The implication being (although not explicitly stated by Freij-Ayoub et al. (2007) that the dunes are swamped and the barrier between Bass Strait and Lake Reeve is breached. This clearly has very significant ramifications regarding ocean ingress to the Gippsland Lakes and the ecology of the Lakes system. Due to the regional (widespread) nature of anticipated lowering of coastal land, the predicted land subsidence is not expected by Freij-Ayoub et al. (2007) to impact on the structural integrity of buildings and infrastructure, although oil and gas pipelines crossing the coast are potentially at greater risk. Freij-Ayoub et al. (2007) stress that the data used to generate these inundation maps is based on a relatively coarse Digital Elevation Model (topographic information) that does not accurately represent coastal landforms along the Gippsland coast, particularly low- lying wetlands and coastal dunes. Hence the extent of inundation may be subject significant errors. Also, the combined subsidence and climate change inundation mapping does not extend east of Rotamah Island due to a lack of data. Further uncertainty exists in the subsidence predictions and inundation models due to remaining doubt regarding stratigraphy and lithology of the Latrobe aquifer. A study of potential coastal erosion due to sea level rise along Ninety Mile beach between Honeysuckles and Paradise Beach (Ethos NRM and Water Technology, 2008) used a high resolution LiDAR Digital Elevation Model and also concluded that a breach in the dunes is possibly (by year 2100), although not over and area as extensive as that suggested by Freij-Ayoub et al. (2007). The implications of a breach in the dunes along Ninety Mile Beach has previously been explored for the Gippsland Lakes Task Force by Sjerp (2008).
Key Conclusions: Coastal Subsidence (From Freij-Ayoub et al. (2007): · Coastal land subsidence is predicted to occur to differing degrees along almost the entire Ninety Mile Beach. · Greatest subsidence is predicted in an area centred on the coast at Golden Beach. · Maximum subsidence under a ‘realistic’ scenario is predicted to be 0.51m by 2031 and 0.48m by 2056. · Maximum subsidence under a ‘pessimistic’ scenario is predicted to be 0.87m by 2031 and 1.2m by 2056. · Any land subsidence along the Gippsland coast will exacerbate the effect of sea level rise and future coastal erosion. · Inundation maps for the combined effect of land subsidence and increased storm tide and wave heights due to climate change predict that under both the ‘realistic’ and ‘pessimistic’ scenarios, the majority of coastal dunes between Seaspray and Rotamah Island are almost entirely inundated. · Significant uncertainties and limitations remain for the data used to generate coastal subsidence and inundation predictions along the Gippsland coast.
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· To date, high resolution ground surveys have not detected any statistically valid land subsidence (other than at the Latrobe Valley open pit coal mines) (AAMHatch, 2006, 2007).
Recommendations: · The predicted coastal inundation resulting from land subsidence and climate change-induced increased sea level / storm tides / wave heights should be re-calculated using new high resolution LiDAR Digital Elevation Model data recently acquired by the Department of Sustainability and Environment. · Undertake specific studies to determine the risk from land subsidence to the serviceability of pipelines (oil, gas, salt water) crossing the coast near the Rosedale Fault System (northeast of Paradise Beach).
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5 COASTAL GEOLOGY, EROSION POTENTIAL AND SEDIMENT TRANSPORT As highlighted in previous sections, the predicted consequences of climate change include sea level rise, changes in weather patterns, changed wind speed and direction (wind climate), changed ocean wave patterns (wave climate), changed storm intensity and storm frequency, and changed rainfall distribution and frequency (CSIRO and BoM). Sea level rise will pose a direct threat to coastal areas, the extent of erosion being dependent upon the erosion potential of the geological formations and rock types present along the coast. Changed weather, storm, wind and wave patterns will also alter coastal processes, particularly sediment transport patterns, and hence could greatly influence the shape of beaches, dunes and shoreline position along the Gippsland coast. This section discusses the geological characteristics of the Gippsland coast, the erosion potential, and changes to sediment transport patterns.
5.1 Coastal Geology and Erosion Potential Surface geology along the Gippsland coast is a useful measure of coastal erodibility and hence can be used to identify vulnerable sites at a regional scale. Geological information available from the Department of Sustainability and Environment was analysed as part of this study to determine the different geological formations present along the Gippsland coast. The broad geological types present along the Gippsland coast are described below and illustrated on Map 1 (at rear). Alluvium: Unconsolidated terrestrial sediment composed of sorted or unsorted sand, gravel, and clay that has been deposited by water. Coastal Dunes: Unconsolidated sands Colluvium: Loose sediment that has been deposited or built up at the bottom of a low grade slope or against a barrier on that slope, transported by gravity. Colluvium often interfingers with alluvium (deposits transported downslope by water). Granite: A coarse-grained, intrusive igneous rock composed predominantly of quartz, feldspars and micas. Limestone: A sedimentary rock composed principally of calcium carbonate. Sandstone: A detrital sedimentary rock composed predominantly of quartz grains, feldspar and rock fragments, bound together by a cement of silica, carbonate or other minerals, or a matrix of clay minerals.
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Sedimentary: A rock formed by the accumulation and cementation of mineral grains transported by wind, water, or ice to the site of deposition or chemically precipitated at the depositional site. Volcanic: Formed from magma and other volcanic flows.
These broad geological types have differing levels of erodibility, depending on their composition, the degree of consolidation and the amount of metamorphism and/or deformation that may have occurred. An indicative ranking of erosion potential is provided below. Highest Erosion Potential - Coastal dunes (Sandy beach) - Alluvium - Colluvium Moderate Erosion Potential - Sandstone - Limestone - Sedimentary * Low Erosion Potential - Volcanic - Granite
*Note: Sedimentary rocks, particularly those that have been subject to metamorphism, may often have a low erosion potential. Based on analysis using Geographic Information system tools, the length of each geological type along the Gippsland coast has been determined and is summarised in Table 5-1 and illustrated in Figure 5-1.
Table 5-1 Proportion of each geological type along the Gippsland coast
Geological Type Erosion Potential Length (km) % of Total Coastal Dunes High 1,233 65.42% Sedimentary Moderate 230 12.23% Colluvium High 148 7.86% Granite Low 141 7.49% Alluvium High 94 5.01% Sandstone Moderate 18 0.96% Volcanic Low 17 0.93% Limestone Moderate 2 0.10% Total 1,884 100.00%
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Highly erodible sediments - Alluvium, Coastal Dunes, 9% 13% Colluvium Moderately erodible areas - 78% Sandstone, Limestone, Sedimentary Low erodibility areas - Granite and Volcanic
Figure 5-1 Proportion of Gippsland Coast threatened by High, Moderate and Low erosion risk Key Conclusions: Geology and Erosion Potential · Highly erodible sediments (Coastal Dunes {including sandy beaches}, Colluvium, Alluvium) comprise approximately 78% of the Gippsland coast. · Moderately erodible areas (Sandstone, Limestone, Sedimentary) comprise about 13% of the coast. This includes sedimentary areas such as the Croajingalong coast that may have a Low erodibility. · Low erodibility areas (Granite and Volcanic) make up approximately 9% of the coast, generally around Wilsons Promontory and other rocky headlands such as Cape Conran. · Importantly, approximately 65% (1,233km) of the Gippsland coast comprises Coastal Dune Systems. These areas are typically low-lying, comprising unconsolidated sediments and hence are highly susceptible to erosion.
5.2 Sea Level Rise and Coastal Erosion Highly erodible sections of the Gippsland coast, as identified above, will be most at risk from the effects of climate change-induced sea level rise and increased storm surges. As sea level rises, erodible shorelines (dunes, sand, alluvium, colluvium) will retreat as beach slope and dune profiles adjust to altered (raised) water levels. The extent of shoreline retreat can be determined for specific locations using ‘storm bite’ analysis based on detailed knowledge of shoreline and dune morphology for a typical 1% AEP storm event (storm surge and tide). Such analysis has been successfully undertaken for sites on the NSW central coast (Cardno Lawson Treloar, 2007). Figure 5.2 illustrates the typical effect of storm waves on sandy beaches. Alternatively, a more generalised indication of shoreline erosion can be obtained by applying the Bruun Rule (Bruun, 1962). This predicts that 1cm of mean sea level rise results in 50cm to 100cm of shoreline retreat, depending on local wave conditions and sand dune characteristics (Figure 5.2). Hence for every 10cm of sea level rise, shoreline recession of between 5 to 10m could be expected. The Bruun Rule is a very simplistic method of determining coastal erosion under conditions of elevated water levels, but it is nevertheless a useful indication in the context of a region-wide study.
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Low energy waves transport sediment onshore
Storm waves and surge erodes upper beach and dunes. Large, high energy waves transport sediment offshore
New eroded beach profile is established.
Elevated water level erodes beach and dunes, resulting in shoreline moving inland.
Figure 5-2 Top: Effect of Storm waves on sandy beach profile Bottom: Bruun Rule beach profile response to sea level rise (after Swartz, 1967)
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The extent of shoreline erosion/recession based on Bruun Rule for various sea level rise scenarios is shown in Table 5.2. If 0.79m sea level rise by year 2100 is applied (based on the IPCC high emission scenario of 0.59m plus up to approx 0.2m for continued ice sheet melt), then sandy shorelines along the Gippsland coast could retreat by as much as 40m to 79m. This scenario is consistent with the Victorian Coastal Council’s 0.8m draft policy position in the draft Victorian Coastal Strategy (VCC, 2007).
Table 5-2 Shoreline erosion/recession based on Bruun Rule for various sea level rise scenarios Projected sea Timeframe, basis and source Shoreline level rise (m) erosion/recession based on Bruun Rule (m) 0.18 Minimum IPCC projection for yr 2100 9 to 18 0.49 CSIRO projection for yr 2070. 24.5 to 49 Used by West Gippsland Catchment Management Authority for planning purposes 0.79 Maximum IPCC projection for yr 2100, based 40 to 79 on 0.59m + 0.2m ice cap melt. Also basis for Victorian Coastal Council upper sea level rise draft policy position of 0.8m >1.0 Rahmstorf projections based on accelerated At least 50 to 100 temperature increase and break-up of polar ice sheet
Detailed work along Ninety Mile Beach between the Honeysuckles and Paradise Beach (Ethos NRM and Water Technology, 2008 – based on data from McInnes et al., 2005a&b, 2006) used a Bruun Rule ratio of 1:75 (1 cm sea level rise results in 75cm shoreline recession) to calculate potential erosion from a 1% AEP storm event (storm surge and tide) under climate change conditions and both a 0.49m and 0.8m sea level rise scenario. This modelling took advantage of the high resolution LiDAR Digital Terrain Model. Results indicated that a 1 in 100 year storm under a 0.8m yr 2100 sea level rise scenario coinciding with flooding in Lake Reeve would result in the barrier dunes between Bass Strait and Lake Reeve being breached at a number of locations (Figure 5.3). Breaches occur where the dune complex is characterised by narrow single crested dunes. A similar situation could easily arise on other coastal dunes fronting smaller estuaries along the Gippsland coast, eg Andersons Inlet, Shallow Inlet, Jack Smith Lake, Lake Tyers, Ewing Marsh and Snowy River. A breach in the barrier dunes along Lake Reeve is also inferred in the results of recent coastal inundation mapping by CSIRO (Freij-Ayoub et al., 2007) that illustrates the combined impact of coastal subsidence and sea level rise. This was previously discussed in Section 4.
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Flooding in Lake Reeve 1 in 100 yr flood level without sea level rise component (1.9m AHD) - thick dashed light blue line. 1 in 100 yr flood level with 0.49m sea level rise component (2.39m AHD) - thin green line. 1 in 100 yr flood level with 0.80m sea level rise (2.7m AHD) - blue water depth shading. Example of theoretical breach in barrier dunes: where coastal erosion and lake flooding intersect
Coastal Erosion 1 in 100 year storm tide level without a sea level rise component (1.4m AHD) – thick red line 1 in 100 year storm tide level with a 0.49m sea level rise component (1.89m AHD) – orange line 1 in 100 year storm tide level with a 0.80m sea level rise component (2.2m AHD) – thin yellow line
Figure 5-3: Potential breach of barrier dunes along Ninety Mile Beach based on ocean storm tide and lake flooding for three scenarios (From: Ethos NRM and Water Technology, 2008
Key Conclusions: Sea Level Rise and Coastal Erosion • Highly erodible sections of the Gippsland coast (dunes, sand, alluvium, colluvium) will be most at risk from the effects of climate change-induced sea level rise and increased storm surges. • A 0.79m sea level rise by year 2100 (based on the IPCC high emission scenario of 0.59m plus up to approx 0.2m for continued ice sheet melt), will result in as much as 40m to 79m erosion/retreat along Gippsland’s sandy coast (using simplistic Bruun Rule calculations). • Modelling of Ninety Mile Beach (Ethos NRM and Water Technology, 2008) indicates that a 1 in 100 year storm under a 0.8m yr 2100 sea level rise scenario coinciding with flooding in Lake Reeve could result in several breaches of the barrier dunes protecting Lake Reeve.
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Recommendations: · Undertake detailed ‘storm bite’ analysis using the high resolution LiDAR DEM at specific high risk locations along the Gippsland Coast as identified in Section 6.
5.3 Wave Modelling and Sediment Transport Projected changes in wind speed and direction through Bass Strait as identified by McInnes et al. (2005a & b, 2006) have been used for this study to carry out numerical modelling of changes to wave conditions and longshore transport patterns along the Gippsland coast. Appendix 1 provides the results of this numerical modelling (Water Technology, 2007). The existing wind and wave conditions for the IPCC “high” and “medium” emissions scenarios for 2070 were modelled to determine the effect of the changed conditions on waves in Bass Strait. Based on the predicted changed wave climate in Bass Strait, the changes to sediment transport patterns were determined for numerous locations along the Gippsland coast, including: · Kilcunda · Venus Bay · Sandy Point · McLoughlins Beach · Seaspray · Lakes Entrance · Marlo · Bemm River · Mallacoota As incident wave energy increases with stronger winds, larger amounts of sediment can be mobilised and transported in both onshore/offshore and alongshore directions. Changes in both gross and net sediment transport were analysed. Gross sediment transport refers to the total volume of sediment being transported along the coast, parallel to the shoreline. This includes transport which is taken off-shore by waves and transported along the nearshore zone by waves and currents. Net sediment transport refers to the difference in the gross sediment transport and represents the dominant direction of transport. The Gippsland coast is oriented roughly east-west, and as such sediment transport is referred to as occurring to the east or west. In reality, localised areas may experience transport in a more northeast or southwest direction, however the general terms used here are east-west transport. Table 5.3 and Figure 5.4 summarise the results of sand transport analysis along the Gippsland coast.
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Table 5-3: Summary of sediment transport analysis for existing conditions versus 2070 climate change estimates
Kilcunda Sediment Transport Potential East West Gross Nett Existing 758000 942000 1700000 -184000 2070 mid emissions 827000 956000 1783000 -129000 2070 high emissions 1018000 1153000 2171000 -135000 % Change in Mid Scenario Transport 9% 1% 5% -30% % Change in High Scenario Transport 34% 22% 28% -27%
Venus Bay Sediment Transport Potential East West Gross Nett Existing 659000 946000 1605000 -287000 2070 mid emissions 728000 973000 1701000 -245000 2070 high emissions 908000 1181000 2089000 -273000 % Change in Mid Scenario Transport 10% 3% 6% -15% % Change in High Scenario Transport 38% 25% 30% -5%
Sandy Point Sediment Transport Potential East West Gross Nett Existing 636000 872000 1508000 -236000 2070 mid emissions 691000 902000 1593000 -211000 2070 high emissions 841000 1105000 1946000 -264000 % Change in Mid Scenario Transport 9% 3% 6% -11% % Change in High Scenario Transport 32% 27% 29% 12%
Mcloughlins Beach Sediment Transport Potential East West Gross Nett Existing 664000 330000 994000 334000 2070 mid emissions 703000 335000 1038000 368000 2070 high emissions 840000 382000 1222000 458000 % Change in Mid Scenario Transport 6% 2% 4% 10% % Change in High Scenario Transport 27% 16% 23% 37%
Seaspray Sediment Transport Potential East West Gross Nett Existing 548000 443000 991000 105000 2070 mid emissions 578000 450000 1028000 128000 2070 high emissions 686000 518000 1204000 168000 % Change in Mid Scenario Transport 5% 2% 4% 22% % Change in High Scenario Transport 25% 17% 21% 60% Lakes Entrance Sediment Transport Potential East West Gross Nett Existing 401000 401000 802000 0 2070 mid emissions 425000 400000 825000 25000 2070 high emissions 511000 469000 980000 42000 % Change in Mid Scenario Transport 6% 0% 3% - % Change in High Scenario Transport 27% 17% 22% -
Marlo Sediment Transport Potential East West Gross Nett Existing 1015000 812000 1827000 203000 2070 mid emissions 1092000 810000 1902000 282000 2070 high emissions 1367000 979000 2346000 388000 % Change in Mid Scenario Transport 8% 0% 4% 39% % Change in High Scenario Transport 35% 21% 28% 91%
Bemm River Sediment Transport Potential East West Gross Nett Existing 1563000 1021000 2584000 542000 2070 mid emissions 1673000 1040000 2713000 633000 2070 high emissions 2055000 1277000 3332000 778000 % Change in Mid Scenario Transport 7% 2% 5% 17% % Change in High Scenario Transport 31% 25% 29% 44%
Mallacoota Sediment Transport Potential East West Gross Nett Existing 3390000 418000 3808000 2972000 2070 mid emissions 3648000 424000 4072000 3224000 2070 high emissions 4664000 529000 5193000 4135000 % Change in Mid Scenario Transport 8% 1% 7% 8% % Change in High Scenario Transport 38% 27% 36% 39%
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Annual Transport (m3) West East -5000000 -4000000 -3000000 -2000000 -1000000 0 1000000 2000000 3000000 4000000 5000000
1. Kilkunda
Kilcunda
2. Venus Bay Venus Bay
3. Sandy Point Existing Transport Sandy Beach
2070 Low Transport 4. Port Albert Port Albert 2070 Mid Transport
5. Woodside Woodside Beach 2070 High Transport
6. Seaspray
Existing Net Seaspray
7. Loch Sport 2070 Low Net Loch Sport
2070 Mid Net 8. Lakes Entrance Kalimna 2070 High Net
9. Marlo
Marlo
10. Bemm River Bemm River
11. Mallacoota Mallacoota Figure 5-4: Sediment Transport – Existing versus 2070 climate change estimates
West of Wilson’s Promontory The sediment transport analysis (Appendix 1) indicates that at locations west of Wilsons Promontory, the existing net sediment transport is in a westerly direction along the coastline. Predicted climate change variations to wind patterns are expected to result in an increase in significant wave heights of approximately 8-10%, however there is expected to be only limited change to the incident wave direction based on this data. The increase in wave heights in areas west of Wilson’s Promontory is predicted to result in an increase in gross sediment transport by up to 30% for the 2070 high emissions scenario. The net westward transport rates may reduce by between 5 to 27% at Kilcunda and Venus Bay depending on the emissions scenario. The existing westward net transport rate at Sandy Point may increase by up to 12% under the 2070 high emissions scenario, but decrease by 11% for the 2070 mid emissions scenario. This illustrates the sensitivity of the coastline to climatic wind changes. Large changes in gross sediment transport along a coastline will cause an increase in the seasonal variability of beach and dune profiles (shoreline location and beach steepness) as more sediment is transported away from a beach in one season before being returned in the next. This could lead to damage occurring as larger amounts of sediment are eroded and transported away from a beach, allowing undermining of dunes to occur, before the sediment is returned on the reverse transport processes to be redeposited. Similarly, increased gross transport may lead to large build-ups alongside coastal infrastructure during certain seasons before the sediment is eroded in the following season.
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East of Wilson’s Promontory For locations east of Wilsons Promontory the existing net sediment transport is in an easterly direction, except at Lakes Entrance where east and west are approximately ‘in balance’. Under the IPCC 2070 high emissions scenario, studied locations (Appendix 1) east of Wilsons Promontory are predicted to experience a significant (21% to 36%) increase in gross sediment transport and between 37% and 91% increase in net sediment transport eastward. This includes Lakes Entrance where eastward net sediment transport will become the dominate process. In addition to the increased seasonal variability to beach and dune systems caused by the increased gross transport rates, as discussed above, the increase in net transport east will result in more sand travelling eastwards. Where there is insufficient sand supply to support this change, erosion and shoreline recession will typically occur at the western end of beach cells, with deposition in the east. These changes would be expected to continue until a new stable profile and beach alignment evolves. Refer to Appendix 1 for complete details of numeric modelling (Water Technology, 2007) and predicted changes to wave conditions and longshore transport patterns along the Gippsland coast.
Key Conclusions: Sediment Transport · Climate change-induced increased wind strength (based on IPCC high and medium emissions scenarios for 2070) will change wave conditions in Bass Strait, leading to changed sediment transport patterns along the Gippsland coast. · Numeric modelling for a 2070 high emissions scenario (Water Technology, 2007) predicts locations west of Wilsons Promontory will experience:
An increase in gross sediment transport resulting in increased seasonal variability to beach and dune profiles, and
Reduced net westward sediment transport (except Sandy Point) · Locations East of Wilsons Promontory are predicted to experience:
Significant increase in gross sediment transport resulting in increased seasonal variability to beach and dune profiles, and
Significant increase in eastward sediment transport, resulting in possible erosion at the western end of beach cells and deposition towards the east.
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6 POTENTIAL IMPACTS AND THREATS TO THE GIPPSLAND COAST
6.1 Overview of Potential Impacts Climate change effecting south eastern Australia is, by the year 2070, projected to cause sea level rise, changed wind speeds and direction, changed ocean wave patterns in Bass Strait, changed storm intensity and frequency, changed rainfall distribution and frequency, and changed coastal sediment transport and geomorphological processes (refer previous sections of this report). In addition to the obvious threat of flooding and coastal inundation caused by sea level rise, these changes will also have a significant, and potentially greater influence on the overall shape of the Gippsland coast. Sea level rise will cause coastal erosion (Section 5.2), which will be further exacerbated by increased storm surge as larger waves are able to propagate closer to shore and cause greater erosion further up the beach face and into coastal dunes. Changes in wind patterns and storminess will affect ocean waves and longer-term sediment transport processes, thereby changing large scale patterns of erosion and sand deposition along the coast (Section 5.3). The most vulnerable coastal sites are low-lying areas and/or those that have a high potential for erosion, and hence shoreline retreat. Section 5.1 demonstrated that 78% of the Gippsland coast is highly susceptible to erosion and is therefore vulnerable to the effects of climate change. The most dramatic potential impact will result from the erosion and breaching of coastal dunes and barrier islands that currently protect inlets, estuaries, low-lying plains and wetlands located immediately behind the dunes and barrier islands. Once eroded, and if the breach is sustained (remains open), the lack of these protective barrier dunes will result in rapid inundation by sea water, increased marine influence, and ultimately creating coastal embayments subject to greater tidal variation, increased wave action and potentially substantially increased erosion and flooding (Ethos NRM, 2008). A sustained breach in a barrier dune complex is most likely to occur following several large storm events, in rapid succession, such that the eroded beach/dunes/islands do not have an opportunity to reform. Several locations along the Gippsland coast could suffer from such large scale geomorphological change, including the Gippsland Lakes at Seaspray, The Honeysuckles and Bunga Arm (Ethos NRM and Water Technology, 2008), at Corner Inlet if the outer islands are eroded to create additional ocean entrances, at Andersons Inlet and Shallow Inlet, at the Snowy River estuary, and at several smaller lakes and estuaries along the Gippsland coast. Coastal erosion, flooding and large scale changes to Gippsland’s coastline caused by climate change not only has the potential to impact on a very broad range of environmental and cultural values, but may also pose a direct threat to an array of physical assets along the Gippsland coast. A summary of these impacts is presented below, based on knowledge gained during this investigation and in-part from previous studies by Sjerp (2002), Bird (2002), Brooke and Hennessy (2005), Fisher (2006), Ethos NRM, 2007, and Ethos NRM and Water Technology (2008).
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Overview: Potential impacts to the Gippsland coast from sea level rise, increased coastal erosion and changed coastal processes · Increased flooding of low-lying areas · Increased inundation from storm surge effect · Increased saline water (tidal) intrusion into estuaries, rivers and coastal embayments · Accelerated coastal erosion due to higher mean water levels and increased storm intensity · Changed beach and dune morphology due to increased erosion and changed sediment transport patterns · Large scale modification to coastal landforms, particularly river deltas and breaching of coastal barrier dunes protecting inlets and estuaries such as the Gippsland Lakes · Potential erosion and loss of barrier dune islands protecting Corner Inlet · Increased wave penetration into ‘breached’ estuaries · Altered inundation frequencies for fringing estuarine wetlands · Ecological collapse of systems unable to tolerate increased marine environment, particularly wetlands and fringing estuarine/riparian vegetation · Modified distribution of fauna species, particularly estuarine-dependent fish and birds · Increased erosion threat to jetties, sea walls, canals, roads, bridges etc · Flooding and loss of efficiency of stormwater drainage systems · Impact on buried services such as power, water, sewer, gas, telecommunications · Saline intrusion into low-lying sewers and pumpwells · Potential loss of Crown land frontage along private coastal land · Threat (including perceived threat) to property values · Altered recreational opportunities along coastal zone.
Possible coastal subsidence along the Gippsland coast between Corner Inlet and Lakes Entrance is summarised in Section 4. Coastal subsidence has the effect of lowering the coastal landscape and hence exacerbates the effect of sea level rise. The potential impacts described above therefore also apply to coastal subsidence, particularly given that the predicted amount of subsidence (up to 1.2m by 2056 for the ‘pessimistic’ scenario) is similar or greater than the worst case global sea level rise projections (0.59m by end of the 21st century plus 0.2+m for accelerated ice sheet melt). An additional potential impact of coastal subsidence relates to altered drainage and hydrology of wetlands and coastal streams as landforms ‘tilt’ during subsidence. The
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The following sections present results of an assessment of environmental and cultural values and infrastructure assets that are potentially at risk due to increased sea level, possible subsidence and changed geomorphological regimes along the Gippsland coast. The assessment is based on risks identified by the study team and on input provided by stakeholders and coastal managers at consultative workshops designed to obtain additional local knowledge and understanding of regional issues. Workshop attendees were presented with the findings of coastal sediment transport modelling and erosion susceptibility to ensure an appropriate appreciation of the potential threats. Annotated aerial photography of the Gippsland coast aided the identification of potentially threatened sites. Maps illustrating the distribution of geological, environmental and cultural values are provided at the rear of this report.
6.2 San Remo to Wilson’s Promontory 6.2.1 Coastal Erosion Potential The coastline from San Remo to Wilsons Promontory is characterised by Rocky shorelines and sandy beaches. The dominant incident wave direction to this section of the coast is limited by the Bass Strait landmasses, and climate change is unlikely to modify the incident directions significantly. However, wave energy will generally increase as a consequence of climate change related increases in wind speed and storminess. The 2070 high emissions projections indicate increased average wind speed, and an increase in annual significant wave height of 8-10% (Appendix 1). Sixty to seventy percent of the coastline between San Remo and Wilsons Prom is coastal dunes or alluvium, of high erosion erosion. Climate change related increases in wave energy alone (ie no change in incident wave angle) is unlikely to result in significant changes to the alignment of the coastal dune sections of this part of the coast. Modelling (Appendix 1) indicates that increased wave energy may result in increased gross sand transport (up to 30% annually) leading to increased inter-annual variability of the shoreline location, and steeper beach profiles during winter. Offshore bar systems may become more well developed in winter and act as a barrier to high wave energy propagating to the shoreline. Sand supply from eroding coastal areas (Inverloch to Cape Liptrap, Waratah Bay) may introduce more sand into the beach systems, supporting the steeper beach profiles and offshore bars. Net longshore transport rates are unlikely to change significantly, as modelling has indicated only small changes in the annual distribution of wave direction. However, with increased wave energy the gross longshore transport rates are likely to increase, leading to greater annual/seasonal variability in shoreline location and beach profile. A long term quasi-equilibrium will re-establish, that will be characterised by wider beaches during summer months and steeper eroded beaches with a significant offshore bar during winter. 6.2.2 Coastal Erosion Threats - Environmental Much of the potentially highly erodible section of this part of the coast is National Parks or Coastal Reserves, classified for the significance in terms of coastal habitat. These areas provide sanctuary for threatened fauna and flora, as well as a range of other
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Page 48 Climate Change, Sea Level Rise and Coastal Subsidence along the Gippsland Coast: Implications for geomorphological features, natural values and physical assets Phase 2 - Gippsland Climate Change Study Final Report Gippsland Coastal Board important species. Increased variability in the location of the beach may result in loss of habitat. Further, the increase in wave energy may result in changes to the entrance conditions at the large estuaries along this section, Anderson Inlet and Shallow Inlet. This could result in changed tidal range within the estuaries with a range of follow on impacts to intertidal habitats. With greater variability in the beaches, smaller estuaries along this section of coast may exhibit changed opening/closing regimes, with ecological as well as flood related impacts. 6.2.3 Coastal Erosion Threats - Cultural The sandy coastline between San Remo and Wilsons Prom has numerous identified sites of significant aboriginal cultural heritage value, many of which are located within National Parks and Coastal Reserves. There are limited sites of European cultural heritage value (identified through the provisions of a Heritage Overlay) with other sites located within Parks and Reserves (eg Lime Kilns at Walkerville). Increased variability in the location of the back beach may result in the loss of some near-coast cultural assets, particularly significant aboriginal sites along the sandy beaches and around Anderson Inlet and Shallow Inlet. 6.2.4 Coastal Erosion Threats – Infrastructure Numerous towns in this section of the coast are vulnerable to coastal erosion, which could result in losses of residential and commercial property, services (water, electricity, sewerage, gas), and roads. Significant threats exist for immediate foreshore areas at Inverloch, Venus Bay, Walkerville, and Waratah Bay due to their proximity to the erodible coast and/or their low elevation. Changes to wave climate may also result in significant changes to the navigability of ocean entrances, particularly at Anderson Inlet, already recognised as a hazardous crossing. Increased sand transport and larger wave conditions could increase navigation risks in this area. 6.2.5 Vulnerable Sites The following table provides a list of potential impacts and/or sites vulnerable to sea level rise and the coastal geomorphological aspects of climate change, based on a high emissions scenario with approximately 0.8m sea level rise by the end of this century. Sites have been identified by the project team and as a result of stakeholder workshops.
Location Asset or Site Potential Threat / Risk San Remo Existing high erosion sites eg near Davis Increased erosion threat Point Road Rock platform (fishing) areas Increased access risk to recreational users Port infrastructure at San Remo Potential erosion threat and reduced navigability due to increased wave climate and potential altered tidal currents Kilcunda - Coastal dune complex Increased erosion threat Powlett River Powlett River estuary Changes to opening and closing regimes Trestle bridge and rail trail Potential erosion threat to sandy substrate
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Location Asset or Site Potential Threat / Risk Kilcunda - Low-lying cemetery land located adjacent to Potential inundation Powlett River river/estuary Low-lying carparks and beach access points Increased risk of inundation Rock platform (fishing) areas Increased access risk to recreational users Low-lying caravan park and accommodation Potential longer-term erosion threat Intake and outfall pipes for proposed Will require adequate burial depth desalination plant under coastal dunes Cape Environmental values associated with Potential loss from increased erosion Paterson National Park and surrounding coastal areas Stormwater outfalls Risk of decreased capacity/efficiency due to increased water levels or inundation by sand Beach-based boat launching sites Changed beach profile and increased wave energy (safety issues) Surf Lifesaving Club Located amongst coastal dunes, potential increased risk of erosion Inverloch and Township foreshore areas Threat of increased erosion Anderson Inlet Stormwater outfalls Risk of decreased capacity/efficiency due to increased water levels or inundation by sand Seawalls Potential over-topping, erosion or undermining Sewer pump stations in low-lying areas Increased risk of inundation Port and boating infrastructure (boat ramps, Increased water levels and erosion jetty) threat Beach access points Increased erosion threat Foreshore caravan park (low-lying land) Potential inundation Foreshore facilities (picnic, toilet and Potential increased erosion and recreational sites) and buildings (Surf inundation threat Lifesaving Club, Yacht Club, Angling Club, Bowling Club) Dinosaur dig site Potential erosion threat Andersons Inlet Increased storm surge flooding inside inlet, and changed opening / closing regimes Increased navigation hazard into Anderson Inlet due to altered entrance currents Trade waste ocean outfall Increased erosion threat if not buried to sufficient depth Venus Bay Township area Increased risk of storm surge and Tarwin inundation Lower Coastal dune complex Increased erosion Life Saving Club Potential longer term erosion risk Road access Potential increase flooding On-site domestic wastewater management Potential increase flooding (septic tanks) Walkerville Coastal dune complex Increased erosion Lime kilns Potential erosion threat Boat/beach ramp Erosion threat and/or sand inundation Beach camping ground Potential erosion threat Waratah Bay Coastal dune complex Increased erosion Township foreshore area Increased risk of storm surge inundation and erosion
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Location Asset or Site Potential Threat / Risk Sandy Point Coastal dune complex Increased erosion Surf Lifesaving Club in dunes Potential increased erosion
Beach access points Increased erosion threat Inlet foreshore Increased storm surge inundation Shallow Inlet entrance changed opening / closing regimes Shallow Inlet Increased inundation of fringing wetlands Boat launching sites on inlet foreshore Increased inundation and potential altered beach profile On-site domestic waste management potential increase inundation at low- (septic tanks) lying sites Wilsons National Park Erosion of dune systems Promontory Potential impact on coastal wetlands / lagoons Potential erosion of numerous coastal cultural heritage site
6.3 Corner Inlet and Nooramunga Coast 6.3.1 Coastal Erosion Potential The Corner Inlet and Nooramunga coast comprises almost entirely of highly erodible alluvium and coastal dunes. Modelling (Appendix 1) shows an 5-10% increase in significant wave height on the Nooramunga coast, which could lead to accelerated erosion and shoreline retreat on the barrier island and southern Ninety Mile Beach areas. Gross sand transport rates may increase by more than 30%, resulting in significant inter-annual variability of the shoreline location and beach profile. Increased wave energy could significantly alter the shoreline position and sediment characteristics. However, the majority of Corner Inlet is relatively sheltered from ocean wave conditions, hence only locally generated waves are likely to be of concern. Projected increases in wind speed over limited fetch conditions will result in slightly larger waves, although the coastal erosion threat is not significantly increased. Barrier islands protecting Corner Inlet (eg Snake Island, Clonmel Island) will however experience significantly changed wave conditions, both in terms of wave energy and direction. Accordingly, these areas will experience significant changes to the longshore transport regime, with increases in both gross and net transport rates likely. Coupling these changes with sea level rise may result in significant erosion of the barrier islands, potentially resulting in entire loss of the smaller islands. This would enable greater intrusion of ocean waves into Corner Inlet, thereby creating potential for increased erosion of the mainland shoreline. 6.3.2 Coastal Erosion Threats - Environmental Increased sea level, storm surge and erosion of barrier islands would result in impacts to fringing wetlands, saltmarsh tidal flats and mangrove stands. Modification and potential loss of these areas would impact on important habitat for a range of fauna, particularly internationally significant bird species.
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Altered water exchange between Corner Inlet and Bass Strait resulting from potential changes to barrier islands and entrance positions, could affect seagrass beds and nursery habitat for fish species. 6.3.3 Coastal Erosion Threats - Cultural Numerous significant aboriginal cultural heritage sites are identified along sandy shorelines throughout Corner Inlet and the Nooramunga coast. Increased erosion of barrier island could impact on these sites. Sites along the mainland shoreline are less likely to be affected, but may suffer from impacts associated with increased storm surge levels and sea level rise. 6.3.4 Coastal Erosion Threats – Infrastructure Sea level rise and increased storm surge could have significant impacts on low-lying towns and associated infrastructure within Corner Inlet. Port Albert for example currently suffers severe stormwater drainage problems due to the lack of hydraulic gradient between the town’s drainage infrastructure and the ocean. Increased sea level and storm surge will further exacerbate these problems. Commercial and recreational boating infrastructure at Port Albert, Port Welshpool and Barry Beach would be affected by increased water levels and sand movement, as would smaller boat ramps at other towns such as Robertsons Beach, Manns Beach, McLoughlins Beach. Increased wave energy within Corner Inlet as a result of erosion or loss of the barrier islands would further impact on coastal infrastructure. Modified entrance and channel locations could adversely affect shipping channels. 6.3.5 Vulnerable Sites The following table provides a list of potential impacts and/or sites vulnerable to sea level rise and the coastal geomorphological aspects of climate change, based on a high emissions scenario with approximately 0.8m sea level rise by the end of this century. Sites have been identified by the project team and as a result of stakeholder workshops.
Location Asset or Site Potential Threat / Risk Corner Inlet Barrier islands Increased shoreline erosion, potential loss of smaller islands Fringing wetlands, mangroves Increased inundation and altered tidal regimes Entrances and channels Altered currents and water exchange between Corner Inlet and Bass Strait
Shipping channels Potentially altered dredging and navigation requirements Multiple seawalls and levee banks Erosion risk, potential over-topping and inundation of low-lying agricultural land Surrounding low-lying agricultural land Potential increased saline intrusion into groundwater Port Franklin Port infrastructure – including jetties, Increased water levels, potential buildings and ramps flooding and potential increased wave energy and currents Foreshore areas Increased erosion and potential inundation of low-lying areas Stormwater outfalls Risk of decreased capacity/efficiency due to increased water levels or inundation by sand Sewage treatment outfall / ponds Increased risk of erosion / inundation
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Location Asset or Site Potential Threat / Risk Toora South / Old inappropriate subdivision Increased risk of erosion and flooding Grip Road Sewage treatment outfall / ponds Increased risk of erosion / inundation Barry Beach Port infrastructure – including jetties, Increased water levels, potential buildings and ramps flooding and potential increased wave energy and currents Communications infrastructure Increased erosion potential of surrounding land Port Port infrastructure – including jetties, Increased water levels, potential Welshpool buildings and ramps flooding and potential increased wave energy and currents Foreshore areas Increased erosion and potential inundation of low-lying areas Sewer pump stations in low-lying sites Increased risk of flooding Stormwater outfalls Risk of decreased capacity/efficiency due to increased water levels or inundation by sand Sewage treatment outfall / ponds Increased risk of erosion / inundation Port Albert Port infrastructure – including jetties, Increased water levels, potential buildings and ramps flooding and potential increased wave energy and currents Foreshore areas Increased erosion and potential inundation of low-lying areas Historic port sites / buildings Potential increased flooding Stormwater outfalls Risk of decreased capacity/efficiency due to increased water levels or inundation by sand Seawalls Elevated water levels – potential accelerated decay of seawalls Robertsons Foreshore areas and nearby dwellings Increased erosion and potential Beach & inundation of low-lying areas Manns Beach Stormwater outfalls Risk of decreased capacity/efficiency due to increased water levels or inundation by sand On-site domestic wastewater management Potential increase flooding (septic tanks) Boat ramp (and jetty) Erosion threat and/or sand inundation McLoughlins Foreshore areas and nearby dwellings Increased erosion and potential Beach inundation of low-lying areas Road access Increased flooding potential Stormwater outfalls Risk of decreased capacity/efficiency due to increased water levels or inundation by sand On-site domestic wastewater management Potential increase flooding / reduced (septic tanks) efficiency Boat ramp Erosion threat and/or sand inundation
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6.4 Ninety Mile Beach and Gippsland Lakes 6.4.1 Coastal Erosion Potential This entire section of coast comprises coastal dune systems, while the Gippsland Lakes have an alluvial or sandy fringe. Accordingly, this section of the coast is highly susceptible to erosion. Gross longshore sediment transport is estimated (based on modelling in Appendix 1) to mobilise approximately 800,000 to 1 million cubic metres of sand per year. The net transport is in an easterly direction, except near Lakes Entrance where the beaches are ‘in balance’. Climate change has the potential to significantly increase the gross transport, and alter the net transport balance. Modelling shows an increase of up to 23% to the gross longshore transport, which would result in increased annual/seasonal variability in the shoreline location. As this section of the coast typically experiences much higher energy than the San Remo to Wilsons Prom section, the impact to coastline variability and beach profile of climate change is considered to be more severe. Changes to the net longshore transport have been modelled with up to 60% increase in eastward sand transport. Coupled with increased variability in shoreline location due to gross transport increases, the impacts could be significant on the open coast, with considerable erosion in areas where there is insufficient sand supply. Modelling of Ninety Mile Beach (Ethos NRM and Water Technology, 2008) indicates that the narrow coastal barrier dunes could be breached by a 1 in 100 year storm event that occurs concurrently with flooding in Lake Reeve (under a 0.8m sea level rise scenario for year 2100). Bunga Arm on the Gippsland Lakes, Jack Smith Lake and Lake Denison are other locations where a potential breach of the barrier dunes could occur. A sustained breach in the barrier dunes is potentially the most dramatic impact of climate change along the Gippsland coast, the implications of which include increased tidal range, altered flood levels, increased impact of storm surge, increased salinity and altered ecological conditions (Ethos NRM, 2008). 6.4.2 Coastal Erosion Threats - Environmental There are National Parks, Ramsar listed wetlands and a variety of significant coastal and estuarine habitats potentially at risk due to changed longshore transport regimes and erosion along Ninety Mile Beach. These areas are host to a range of fauna species, including colonies of shore birds, waders and the vulnerable Little Tern. Significant coastal erosion may affect these species through loss of roosting and breeding habitats. Should there be a significant ocean breach into the Gippsland Lakes, Jack Smith Lake or Lake Denison, the potential ecological impacts to these Lakes and estuarine systems would be significant (Ethos NRM, 2008) and could include: · Increased intrusion of ocean water · Increased salinity of the lakes and waterbodies · Potential increased wave penetration into waterbodies · Increased penetration of tidal prism · Increased inundation of fringing wetlands, saltmarsh and intertidal zone
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· Increased shoreline erosion – particularly river deltas and sandy spits · Altered distribution (or potential loss) of fauna and flora species due to changed environmental / habitat conditions · Introduction of new species (including weeds and pest animals) due to changed environmental conditions, eg Mangroves could establish in the Gippsland Lakes 6.4.3 Coastal Erosion Threats - Cultural Dunes of Ninety Mile Beach and the shores of coastal estuaries, particularly the Gippsland Lakes, are rich in aboriginal cultural heritage sites. Increased erosion of the barrier dunes and lake shorelines could expose these sites, as is the case currently at Round Head on the Gippsland Lakes. Sites of European cultural significance are less widespread along this section of the Gippsland coast, being limited to urbanised settlements such as Lakes Entrance. 6.4.4 Coastal Erosion Threats – Infrastructure Along Ninety Mile Beach there are relatively few settlements or built infrastructure that could be threatened by increased erosion and changes to longshore sediment transport patterns. However, there are numerous townships and settlements surrounding the Gippsland Lakes that could be threatened by increased water levels due to sea level rise, particularly if there is a sustained breach to the barrier dunes along Ninety Mile Beach. Woodside Beach and Seaspray are located immediately behind coastal dunes with surf lifesaving clubs situated on vulnerable sites where dune erosion could pose a significant threat. Gas and outfall pipelines under coastal dunes at several locations along Ninety Mile Beach could be threatened if buried to insufficient depths. Increased water levels in the Gippsland Lakes, and the impact of a potential breach in the barrier dunes would pose a significant threat to low-lying infrastructure at numerous towns and settlements surrounding the Lakes, including, Hollands Landing, The Honeysuckles, Paradise/Golden Beach, Loch Sport, Paynesville, Raymond Island, Eagle Point, Metung and Lakes Entrance. Port infrastructure, including channels and sand bypassing pumps in the entrance at Lakes Entrance could be affected by increased water levels and altered sediment transport patterns. 6.4.5 Vulnerable Sites The following table provides a list of potential impacts and/or sites vulnerable to sea level rise and the coastal geomorphological aspects of climate change, based on a high emissions scenario with approximately 0.8m sea level rise by the end of this century. Sites have been identified by the project team and as a result of stakeholder workshops.
Location Asset or Site Potential Threat / Risk Coastal Jack Smith Lake and Lake Denison Potential changes entrance dynamics Estuaries or breech of dunes and increased inundation by ocean waters – will impact on ecology of estuarine system Woodside Surf club and observation tower located in Potentially threatened by dune erosion Beach dunes Pedestrian beach access paths Threatened by dune erosion
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Location Asset or Site Potential Threat / Risk Woodside Carpark and recreation areas behind dunes Potentially threatened if dunes are Beach severely eroded Foreshore caravan park Potentially threatened if dunes are severely eroded or breached Seaspray Coastal dunes Erosion and loss of dune vegetation Surf club located in dunes Threatened by dune erosion Pedestrian beach access paths Threatened by dune erosion Foreshore caravan park and recreation Potentially threatened if dunes are areas behind dunes severely eroded Low-lying dwellings and roads Potentially threatened if dunes are breached and ocean inundates Lake Reeve New sewer and low-lying pumpwells Potential inundation if extreme flooding in Lake Reeve Stormwater Risk of decreased efficiency due to increased water levels Beach access points Increased erosion threat The Honey- Coastal dunes Erosion and loss of dune vegetation suckles Low-lying dwellings and roads Potential inundation if extreme flooding in Lake Reeve Further threatened if dunes are breached Paradise/ Coastal dunes Erosion and loss of dune vegetation Golden Beach Low-lying dwellings, roads and causeway Potential inundation if extreme flooding in Lake Reeve Further threatened if dunes are breached On-site domestic wastewater management Potential increase flooding (septic tanks) Ninety Mile Gas delivery and Outfall pipes (saline water Potentially threatened if buried to Beach and treated wastewater) insufficient depths Beach access points Increased erosion threat
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Location Asset or Site Potential Threat / Risk Gippsland Gippsland Lakes waterbodies and fringing · Potential Breach of barrier dunes Lakes wetlands · Increased intrusion of ocean water · Increased salinity of waterbodies · Potential increased wave penetration into waterbodies · Increased penetration of tidal prism · Increased inundation of fringing wetlands, saltmarsh and intertidal zone · Increased shoreline erosion – particularly river deltas and sandy spits · Altered distribution (or potential loss) of fauna and flora species due to changed environmental / habitat conditions · Introduction of new species (including weeds and pest animals) due to changed environmental conditions, eg Mangroves could establish · Altered river deltas – eg potential avulsion of Mitchell River into Jones Bay · Potential increased erosion of Aboriginal heritage sites eg Round Head Gippsland All townships and settlements surrounding Lakes Gippsland Lakes, including: Seacombe, townships Hollands Landing, Loch Sport, The Grange, Paynesville, Raymond Island, Eagle Point, Metung, Mosquito Point, Barrier Landing and Lakes Entrance Low-lying dwellings, roads and commercial Potential inundation if extreme flooding areas (and canals at Paynesville) in Gippsland Lakes Sewers and low-lying pumpwells (in sewered Potential saline infiltration of buried townships) sewers. Potential inundation of pumpwells during flood events On-site domestic wastewater management Potential increase flooding (for areas with septic tanks) Stormwater Risk of decreased efficiency due to increased water levels at outfalls Jetties, boat ramps, berths and other boating Increased water levels may impact on infrastructure operational efficiency. Potential erosion threat Foreshore recreation facilities Potential threat of foreshore erosion (where seawall is absent) Lakes Entrance Golf Club Potential inundation from Cunninghame Arm Camping areas in Parks and Reserves Potential increased shoreline erosion surrounding Gippsland Lakes Potential inundation of campsite toilets Entrance at Port, dredging and sand by-pass Potentially affected by increased water Lakes infrastructure levels and altered coastal sediment Entrance transport patterns
The extent of flooding at Lakes Entrance under increased sea level and flood conditions has been modelled using survey data and Geographic Information System (GIS)
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Figure 6-1 Flood inundation at Lakes Entrance for 0.0m AHD (top), 1.0m AHD (middle), and 2.0m AHD (bottom) (Source: Wheeler, P., 2008)
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6.5 Lakes Tyers to NSW Border 6.5.1 Coastal Erosion Potential The Gippsland coast east from Lake Tyers to the NSW border is characterised by long sandy beaches interspersed with numerous large rocky headlands and, towards the east along the Croajingalong Coast, by rocky shorelines. Modelling (Appendix 1) suggests up to 36% increase in gross sediment transport and between 39 to 91% increase in the amount of sediment transported in an easterly direction. Hence, much of this section of the Gippsland coast will be susceptible to erosion caused by sea level rise and the projected increased sediment transport regimes. Erosion will occur until a new stable beach profile evolves, except at the western end of beach cells where sediment supply is insufficient. 6.5.2 Coastal Erosion Threats - Environmental Much of the coastline fringes Cape Conran Coastal Park, Croajingalong National Park and a number of Reserves (Ewings Marsh), which provide a broad range of habitats that are host to a great variety of fauna species, many of which are restricted to the eastern end of the Victorian coast. This section of the Gippsland coast also has a number of important estuaries that are in excellent condition, including Lake Tyers, Sydenham Inlet, Tamboon Inlet, Wingan Inlet and Mallacoota Inlet. Erosion of coastal areas, and potential changes to estuary entrances, has the potential to impact on coastal habitats and significantly alter ecological conditions within estuaries, similar to the scenario described above for the Gippsland Lakes. Changed longshore sediment transport patterns will alter the conditions at ocean entrances to smaller estuaries, which, depending on sediment supply, could result in either prolonged entrance closures or more frequent natural opening. 6.5.3 Coastal Erosion Threats - Cultural The coast east of Lake Tyers, particularly the Croajingalong coast and around estuary shores, abounds with sites of aboriginal significance. Increased erosion of coastal dunes and estuary shores may result in exposure and possible loss of some of these sites. Sites of European cultural significance are less widespread along this section of the Gippsland coast, being limited to small urbanised settlements and historic sites such as Point Hicks Lighthouse. 6.5.4 Coastal Erosion Threats – Infrastructure There is very limited built infrastructure along the open coast between Lake Tyers and the NSW border. Most assets are associated with small townships located immediately inland on the shores estuaries. Changes to estuary entrance dynamics may result in increased water levels within estuaries (from sea level rise) if the entrance becomes predominantly open, or could result in flooding (from river inflows) if entrances remain closed for prolonged periods. Increased water levels and flooding has the potential to significantly impact on low-lying areas of townships surrounding coastal estuaries. 6.5.5 Vulnerable Sites The following table provides a list of potential impacts and/or sites vulnerable to sea level rise and the coastal geomorphological aspects of climate change, based on a high
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Page 59 Climate Change, Sea Level Rise and Coastal Subsidence along the Gippsland Coast: Implications for geomorphological features, natural values and physical assets Phase 2 - Gippsland Climate Change Study Final Report Gippsland Coastal Board emissions scenario with approximately 0.8m sea level rise by the end of this century. Sites have been identified by the project team and as a result of stakeholder workshops.
Location Asset or Site Potential Threat / Risk Estuarine Includes lake Tyers, Snowy River, Similar potential impacts to ecological Inlets Sydenham Inlet, Tamboon Inlet, Wingan characteristics as described above for Inlet and Mallacoota Inlet Gippsland Lakes Lake Tyers Estuary entrance Altered entrance dynamics Coastal dunes Erosion and loss of dune vegetation Foreshore car parks and boat ramps Potentially threatened if entrance is breached or remains open more frequently Foreshore recreation facilities Potential threat from foreshore erosion Sewers and low-lying pumpwells Potential inundation of pumpwell Low-lying hotel and dwellings Potential inundation Jetties Increased water levels may impact on operational efficiency Beach access points Increased erosion threat Ewing Marsh Coastal dunes Erosion and loss of dune vegetation Potential breach of barrier dune Marlo Estuary entrance on Snowy River Altered entrance dynamics Coastal dunes Erosion and loss of dune vegetation Foreshore car parks, boat ramp and yacht Potentially threatened if entrance is club breached or remains open more frequently Jetties Increased water levels may impact on operational efficiency. Foreshore recreation facilities Potential threat from foreshore erosion Sewers and low-lying pumpwells Potential inundation of pumpwell
Gas supply lines from Bass Strait Potentially threatened if buried to insufficient depths Low-lying dwellings and road Potential inundation from raised water levels and extreme flooding in Snowy river Stormwater Risk of decreased efficiency due to increased water levels at outfalls Cape Conran Beach access paths Threatened by increased erosion Jetty and boat ramp Increased water levels may impact on operational efficiency. Bemm River Estuary entrance on Sydenham Inlet Altered entrance dynamics Coastal dunes Erosion and loss of dune vegetation Foreshore car parks, boat ramp and yacht Potentially threatened if entrance is club breached or remains open more frequently Foreshore recreation facilities Potential threat from foreshore erosion Low-lying dwellings, hotel and roads Potential inundation from raised water levels and extreme river flooding On-site domestic wastewater management Potential increase flooding (septic tanks) Jetties and boat ramp Increased water levels may impact on operational efficiency. Potential erosion threat
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Location Asset or Site Potential Threat / Risk Tamboon Estuary entrance on Tamboon Inlet Altered entrance dynamics South Coastal dunes Erosion and loss of dune vegetation Low-lying dwellings Potential inundation from raised water levels On-site domestic wastewater management Potential increase flooding (septic tanks) Jetties Increased water levels may impact on operational efficiency. Wingan Inlet Low-lying campsites Potentially threatened by increased & other erosion and elevated water levels smaller inlets Coastal dunes Erosion and loss of dune vegetation Dock Inlet Potential breach of entrance dunes Mallacoota Inlet entrance Altered entrance dynamics
Coastal dunes Erosion and loss of dune vegetation Foreshore recreation facilities Potential threat of foreshore erosion (where seawall is absent) Foreshore caravan park Potential inundation and flooding Sewers and low-lying pumpwells Potential inundation of pumpwells during flood events
Low-lying dwellings and roads (limited in Potential inundation and flooding number) Sewers and low-lying pumpwells Potential inundation of pumpwell Stormwater Risk of decreased efficiency due to increased water levels at outfalls Jetties, boat ramps, berths and other boating Increased water levels may impact on infrastructure operational efficiency.
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7 Adaptive Management for Sea Level Rise and Climate Change along the Gippsland Coast
7.1 Adaptive Management Adaptive management, in the context of this study, refers to how both humans and natural systems respond to the impacts of climate change, sea level rise and coastal subsidence along the Gippsland coast. The process relies on knowledge of the likely impacts and an understanding of the options available to minimise the impacts and maximise any possible advantages (Pittock, 2003). Response to climate change and sea level rise needs to be both pro-active, comprising increasing community awareness and planning for change, and re-active responses (Pittock, 2003; Bell et. all, 2001; AGO, 2006a&b), which involve either: · Doing nothing, · Retreating from impacted areas, · Adapting to (or accommodating) the change, or · Protecting (or defending) an area against the impact of the change. An important aspect of adaptive management is to remain flexible and adjust response options as knowledge of climate change impacts improves. Many of the threats posed by climate change and sea level rise along the Gippsland coast are an intensification or worsening of existing issues. Inappropriate subdivision along the Wellington coast, for example, currently suffers from flooding and coastal erosions threats, which will be intensified by sea level rise, increased wave activity and coastal subsidence. Further, the current tools and planning instruments are not well suited to adaptive and flexible management of the coastline. Changes to the planning scheme and the introduction of additional planning ‘overlays’ can be time consuming, costly, and often require considerable ‘interpretation’ in consideration of local factors. Accordingly, adaptive management actions in Gippsland need to carefully consider their impact on existing and future community needs and expectations.
7.2 Pro-active Response to Climate Change Threats A number of pro-active management options are available that will allow appropriate communication and planning in addressing climate change-related threats along the Gippsland coast. These include continuing to raise the awareness of the potential threats to coastal communities, environmental and heritage assets, as well as public and private infrastructure. In addition, planning for growth and development in the region needs to take into consideration the threats of climate change. 7.2.1 Awareness Raising Continued raising of community awareness will be a challenge over the next decade. Media attention and ‘sensationalist’ journalism fuels skepticism which will reduce the community’s willingness to accept management actions. Informed and balanced coverage of the threats of climate change and coastal subsidence, through projects
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Page 62 Climate Change, Sea Level Rise and Coastal Subsidence along the Gippsland Coast: Implications for geomorphological features, natural values and physical assets Phase 2 - Gippsland Climate Change Study Final Report Gippsland Coastal Board such as this one, will demonstrate that management planning and decision making is being undertaken based on the best available science. Continued engagement of stakeholders, both at the senior management levels, as well as ‘on-the-ground’ will also be important so that a clear and consistent message can be circulated at all levels. This will further assist in ensuring actions are adopted and accepted within the community. The Gippsland Coastal Board will continue to play a vital role in engaging with community members, industry, Local Government and other Government agencies. 7.2.2 Future Planning Planning for future growth along the Gippsland coast needs to consider the threats of climate change. Authorities such as local municipalities, Catchment Management Authorities and the Gippsland Coastal Board have responsibilities to identify hazard- prone areas and to manage these risks, develop and apply appropriate development policies and standards. A policy could be developed for the Gippsland coastal region that references appropriate sea level rise projections, and recognises the uncertainty in the science. Such policy could be applied though existing planning schemes, via additional or alternative ‘overlay’, or more detailed local development controls. These policies would essentially prescribe setback distances from low-lying areas and describe under what circumstances development was not permitted within the setback area. The policies would also need to set out appropriate permitted land use within the setback areas and give consideration existing landuse. State and Commonwealth Governments should provide clear policy direction regarding anticipated sea level rise and coastal subsidence impacts through proclaiming a statutory projected sea level rise and/or erosion setback, depicted as an overlay (or development) control in municipal planning schemes The existing Land Subject To Inundation Overlay (LSIO) provides an instrument to apply such a policy with respect to sea level rise (and coastal subsidence). However, coastal erosion, and the threats associated with the potential breaches of coastal barrier dunes may need to be considered via an alternative planning scheme tool. It may be appropriate to include coastal erosion threats within an Environmental Significance Overlay (ESO), such as currently used to protect ecologically sensitive coastal habitats. Planning appropriate emergency response procedures for people in threatened areas and townships identified in this report is also vital to ensure that risks to the community during future storm or flood event are minimized. A planning policy for areas potentially threatened by climate change-induced sea level rise has been prepared by the Western Australian Planning Commission. The policy is based on a Bruun Rule response (refer to Section xx) and provides a useful starting point for development of a similar setback policy for the Gippsland coast, particularly given the dominance of sandy shorelines. The setback to allow for sea level rise is based on the mean of the median model of the latest Assessment Report of the IPCC Working Group. The vertical change predicted by the current model between the years of 2000 and 2100 is 0.38 metres [for IPCC, 2001]. A multiplier of 100, based on the Bruun Rule shall be used and gives a value for 38 metres for sandy shores [for IPCC, 2001]. For other shore types, [this distance] shall be assessed in regard to local geography.
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WAPC State Coastal Planning Policy No 2.6
Key Strategies: Pro-active Response to Climate Change Threats The Gippsland Coastal Board will take a lead role in: · Facilitating on-going research into potential impacts of climate change on the Gippsland coast · Increasing community awareness of the potential impacts of climate change on the Gippsland coast Local Government and the Department of Planning and Community Development should take a lead role in: · Pro-active planning to develop appropriate land use planning policies to cater for future climate change and sea level rise along the Gippsland coast.
7.3 Re-active Response to Climate Change Threats Re-active responses to climate change threats involve implementing a range of actions based on the immediate and short-to-medium term threats posed by climate change and sea level rise. Choosing the appropriate action will require considerable consultation with the community and stakeholders to gain acceptance, and to determine the level of risk acceptable for specific locations. 7.3.1 Do Nothing In many areas along the Gippsland coast (especially remote areas), the Do Nothing option will be the preferred management response, as there will be limited opportunity to prevent the predicted impact, and the loss resulting from the impact will be relatively minor when placed in context of regional and global change. For example, sea level rise and increased storm activity may lead to losses of coastal dunes and wetlands in the Jack Smith Lake area along Ninety Mile Beach. Ocean waves spilling into these areas may result in loss of the freshwater wetlands, and changes as this system evolves from freshwater to saltmarsh dominated ecosystem. In allowing these changes to evolve, there is recognition that one ecosystem is ecologically no better that the other, only different. Action required to preserve the freshwater systems would be extremely expensive and probably ultimately ineffective. The response in such situations would be to do nothing to stop the change, but to recognize the impact of the change. Where appropriate, studies should be initiated to document those areas with high potential to be lost or changed by climate change related impacts, and to implement ongoing monitoring to study the evolution from one system to another. There are large areas of the Gippsland coast with significant aboriginal heritage value. Many of these are located in coastal dunes or along sandy shores and may be lost as a result of sea level rise. There may be little that can be done to prevent such losses. Nevertheless, the opportunity exists now to implement studies to document these heritage values before they are lost. Similarly for other archeological sites throughout the region.
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For other infrastructure in the coastal dunes, it may be appropriate to do nothing until it is threatened, and then act. For example, it may be considered appropriate to keep surf living saving clubs on the dunes until they are threatened, and then relocate the building closer to the end of it engineering life. Provided the risks are well known, and there has been adequate emergency planning, the overall risk could be considered low. For many environmental and cultural assets, there will be limited opportunity to implement management options to prevent the impacts of climate change and sea level rise, but by identifying those areas at risk, appropriate action can be taken to benefit future generations and expand our knowledge base. 7.3.2 Planned Retreat Planned retreat refers to the deliberate relocation of assets that are threatened by the projected impacts of climate change. This action should be taken with full knowledge of the likely impacts and a comprehensive understanding of the costs and benefits of relocation verses alternative responses. Hence stakeholders with infrastructure and other built assets potentially at risk will benefit from detailed, site-specific studies to assess the projected impacts of climate change, and from knowing the life expectancy and replacement cost of assets. Planned maintenance and upgrading of assets can be implemented in consideration of the climate change threats, and appropriate alternative strategies incorporated into existing management structures. For example, sewer pump stations require maintenance and have a lifecycle of 15-30 years, depending on usage. Planned replacement activities would see alternative strategies employed, such that new facilities are constructed further inland or on higher ground, to avoid the risks of sea level rise and/or coastal erosion. On a larger and far more complex scale, entire communities and dwellings may need to be relocated because the cost of protecting such areas from erosion and/or flooding is prohibitively high, particularly when on-going maintenance of protective measures is included. Some low-lying dwellings and coastal communities along the Gippsland coast may ultimately find that a managed relocation by retreating to higher ground is the only cost-effective long term response option. On-going protection measures such as dykes, levee banks, sea walls and pumps could be effective in the short term but would require considerable maintenance/replacement and upgrading over time. The entire concept of a planned retreat of private dwellings would no doubt create immense community angst and need to be very sensitively managed with considerable Government input. Major issues such as equitable treatment of all assets, compensation and land availability for relocation would need to be addressed. Importantly, it should be recognised that sea level rise may continue well past 2070 or 2100 irrespective of the changed emissions over the next few decades. Therefore, major planned retreat strategies should consider timeframes much longer than the end of the century when identifying potential relocation sites. Relocation needs to be based on setback limits prescribed in planning schemes (where they have been developed), but it needs to be recognised that the limits may change as new and more accurate projections are delivered as the science of climate change advances. 7.3.3 Adaptation Adapting to the impacts of climate change and sea level rise is a strategy employed where the asset, be it a small piece of infrastructure or a dwelling, is modified in such a way that the impacts are minimised or accommodated to enable its continued use at the
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Page 65 Climate Change, Sea Level Rise and Coastal Subsidence along the Gippsland Coast: Implications for geomorphological features, natural values and physical assets Phase 2 - Gippsland Climate Change Study Final Report Gippsland Coastal Board same location. This could involve actions such as elevating roads and dwellings above the threatened flood level, or modifying jetties and boat ramps so that they remain operational at higher water levels. For natural systems such as wetlands or dunes, adaptive responses could involve implementing works that anticipate the predicted change to an ecosystem and work with that change rather than against it. For example, the progressive landward migration of wetlands and coastal dunes could be catered for as a planned change in landuse rather than being perceived as a threat. Adaptation strategies that require physical works or modification to assets are likely to be costly and have flow-on effects to other assets/sites. Such strategies are often likely to be closely associated with related ‘protection works’. Hence the long term cost- effectiveness of, for example, raising buildings will also need to consider broader strategic planning issues such as access and the desirability (risk) of assets remaining in a threatened area. 7.3.4 Protection High value assets that are required at a specific fixed location, for example a telecommunications tower, could be protected from the threats of sea level rise through construction of sea walls, levees and/or pumps. Similarly, following detailed risk and cost analysis, it may prove to be both viable and more cost-effective to protect entire townships rather than relocate them through a planned retreat to higher ground. The value of assets and the availability of a site for relocation will be critical issues in determining whether or not threatened towns like Lakes Entrance, with extensive areas of low-lying buildings, large private buildings (apartment blocks) and a considerable commercial area, are ultimately relocated or protected. The maintenance/replacement and upgrading costs of protective works will also need to be considered. In certain situations, protection of a public or private asset may be an interim solution to minimise flooding and/or erosion for the remainder of its ‘engineering life’ (for example an electricity sub-station, boat ramp, or sewer pump station), prior to it being relocated at some future time when the asset needs replacement. A variety of natural assets and ecological systems may also be protected, for both the short and long term. For example, it may be viable to protect a particularly good example of freshwater wetland from increased marine inundation by constructing levee banks that prevent flooding with saline water. However, such protective works would only be justifiable if the asset being protected was particularly rare or threatened with ‘extinction’. Given the likely high cost of protective works, it may be more appropriate in such instances to allow the transformation over time of natural systems to a new adjusted state, and encourage ‘replacement ecosystems’ at a new more favorable location. Such decisions would therefore need to be based on a variety of factors including conservation status of asset, abundance of asset, cost of protective woks, likelihood of success, and alternative opportunities. Protective works in some areas may take the form of a ‘softer’ solution comprising beach nourishment, revegetation of dunes and foreshores, or estuarine restoration to reduce the impact of sea level rise.
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7.4 Risk Management Effective management of identified climate change and sea level rise risks along the Gippsland coast can be achieved via a range of initiatives, dependent on the nature of the risk, its magnitude and potential consequence. It will be important for stakeholders and asset managers to understand the magnitude and consequence of the climate change risk as it pertains to them. Where do nothing and planned retreat strategies are adopted, risk management and emergency planning will be required to ensure these risks are adequately identified with appropriate planning is in place. A vital component of adequate risk management involves being able to make balanced decisions regarding the most appropriate action, based on the magnitude of the risk, its consequences, the cost of taking action and the preparedness of the community to both pay for action and ‘forego private rights’. The key step towards being able to make informed and consistent decisions is for Government to provide clear policy direction regarding anticipated climate change and sea level rise impacts through proclaiming a statutory projected sea level rise and/or erosion setback, depicted as an overlay or development in municipal planning schemes. Local Government will need considerable support from State and Commonwealth Government to enable adequate planning and risk management tools to be incorporated into decision making frameworks such as municipal planning schemes.
Key Strategies: Pro-active Responses to Climate Change Threats Do-Nothing Response The Do-Nothing Response to climate change and sea level rise threats along the Gippsland coast may be the most appropriate response where the threatened ‘asset’ (natural or built): · Can not be effectively protected, · Will change ecological character but not be totally lost, or · Will be replaced or relocated anyway at some time in the near future. Planned Retreat · The Planned Retreat Response to sea level rise threats along the Gippsland coast may be the only cost effective long term solution for individual assets and possibly even entire low-lying coastal communities. · Planned retreat of private property will create immense community angst. · Leadership from Government will be required to address key issues such as equitable treatment of all assets (public and private), compensation and land availability for relocation. Adaptation Strategies · Adapting or modifying existing physical assets should consider not only the cost-effectiveness of such actions, but also the broader strategic issues related to an asset remaining in a threatened location.
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Key Strategies: Pro-active Responses to Climate Change Threats Protection Strategies · High value physical assets may warrant protection from sea level rise, either for the sort term until replaced at a new site, or for the longer term if it is more cost effective to implement protective works and if there is no practical alternative site for relocation. · ‘Rare’ or poorly represented natural ecosystems along the Gippsland coast could justifiably be protected if the impact from sea level rise resulted in their total loss. Policy Direction and Government Support · Government should provide clear policy direction regarding anticipated climate change and sea level rise impacts through proclaiming a statutory projected sea level rise and/or erosion setback, depicted as an overlay or development control in municipal planning schemes. · Local Government will need considerable support from State and Commonwealth Government to enable adequate planning and risk management tools to be incorporated into decision making frameworks such as municipal planning schemes.
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8 RECOMMENDATIONS FOR FUTURE WORK There are numerous areas of continued research to better understand climate change and sea level rise threats along the Gippsland coast. Better understanding of the climate models and ways to evaluate and deal with the uncertainty. Within the Gippsland region, there are specific actions that can be undertaken at a local scale to improve our preparedness for climate change. Key areas include: • Continuing to improve climate change models and erosion analysis to better evaluate and deal with remaining uncertainty. • Improving local knowledge of the geology along Gippsland’s coastline, to better identify those areas at risk of erosion. • Improving topographic / terrain data, to understand the magnitude of the flooding and erosion risks to communities along the Gippsland coast. • The extent of inundation resulting from coastal subsidence along the Gippsland coast should be re-modelled using detailed coastal digital elevation models based on new high resolution LiDAR data. • Action by local government to incorporate adequate planning and risk management tools into decision making frameworks. • Adaptive management planning by regional stakeholders to identify appropriate action to address threats to assets under their responsibility. These are discussed in further detail below.
8.1 Improved Climate Change and Sea Level Rise Models As more information becomes available regarding actual greenhouse gas emissions and actual global temperature rises, climate change and sea level rise modelling specific to the Victorian coast should continue to be refined so as to reduce remaining uncertainties surrounding the extent of sea level rise and the severity of resulting coastal erosion. Storm bite analysis using detailed coastal digital elevation models (based on new LiDAR data) should be undertaken at key threatened sites (as identified in Section 5.2) to quantify the precise extent of coast erosion and shoreline recession.
8.2 Geological Survey Existing geological mapping along the Gippsland coast is at a scale of 1:25,000. This is inadequate to resent local coastal geological features at a scale suitable for local action planning. Improved, more accurate data would significantly assist in identifying, with a higher degree of confidence, areas potentially subject to erosion due to storms and climate change related impacts.
8.3 Detailed Topographic / Terrain Data Accurate estimates of risk relating to sea level rise, storm surge inundation and coastal erosion relies heavily on a very accurate knowledge of coastal topography. Existing survey data is insufficiently accurate in terms of extent and resolution, both horizontal and vertical.
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The Department of Sustainability and Environment (DSE) has launched a program to collect Airborne Laser Scanning (ALS), or LiDAR aerial survey data along the entire Victorian coast. Data for a portion of the Gippsland coast (from Honeysuckles to Golden Beach) has already been collected and processed. High resolution LiDAR data will provide terrain information at accuracies of ±0.15m. Existing flood level information (held by DSE), storm surge data from CSIRO and wave data can then be plotted over the new terrain data to better identify risks throughout the region. The mapping should quantify the risks in terms of depth of inundation, frequency of inundation and duration to assist Local government and emergency response organisations in focussing planning efforts and providing guidance on which areas require urgent attention in the application of adaptive management strategies.
8.4 Inundation due to Coastal Subsidence Once the high resolution LiDAR data is captured and a detailed digital elevation model is prepared for the section of Gippsland’s coast threatened by coastal subsidence (Corner Inlet to Lakes Entrance), the extent of inundation due to the combined effect of sea level rise and subsidence should be re-modelled using the subsidence parameters outlined in the most recent CSIRO investigation (Freij-Ayoub et al., 2007). This will produce a more accurate map of threatened sites and better depict the extent to which the barrier dunes along Ninety Mile Beach could be breached.
8.5 Action for Local Government Local government and emergency response organisations are responsible for much of the emergency planning along the Gippsland coast, responding (in partnership with VicSES) to flooding and coastal erosion events. Geology and terrain information, discussed above, will provide the basis for the development of emergency response actions delivered via the Municipal Emergency Management Plan (MEMP). Local government should act to identify specific risks, classify these risks and set out the appropriate emergency response. State and Commonwealth governments should provide clear policy direction for Local government regarding anticipated climate change and sea level rise impacts through proclaiming a statutory projected sea level rise and/or erosion setback. In consultation with DSE and regional stakeholders, Councils should be responsible for implementing new and/or revised planning controls to address climate change risks. Development of these new planning tools and/or instruments will require careful consideration of community benefit within the context of uncertainty associated with future climate change. In addition to depicted projected sea level rise and/or erosion setbacks as overlays in municipal planning schemes, Local government could also consider Coastal Action Plans (prepared by regional Coastal Boards) and specific local Development Control Plans as alternative (or additional) planning tools. Targeted plans would recognise that planning in the coastal zone has inherent uncertainty that requires case by case consideration.
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8.6 Regional Stakeholders Regional stakeholders with ownership and management responsibility over cultural, environmental and infrastructure assets (private and public) will need to continue being informed about climate change threats. Ongoing management and maintenance planning should be reviewed to include adaptive management actions to ensure assets are protected, relocated or removed as appropriate. This adaptive management planning will be challenging, as the region’s population continues to grow, and demand on the assets increases.
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9 CONCLUSION The Gippsland coast is rich and diverse in natural and cultural values. The coast also supports settlements and townships that vary considerably in the size and distribution along the coast. Physical assets associated with these built up areas range from isolated boat ramps and jetties to valuable private properties fronting prime foreshore land. Climate change, sea level rise and coastal subsidence all have the very real potential to significantly impact on the Gippsland coast, affecting both natural values and built infrastructure, on private and public land. Previous investigations by the Intergovernmental Panel on Climate Change (IPCC), CSIRO, the Bureau of Meteorology and others have demonstrated the extent to which global warming will change climatic conditions and cause sea level rise, at a global and local scale. The IPCC (2007a) has projected that sea level will rise by up to 0.79m (0.59m plus 0.20m from additional ice sheet melt) by the end of this century, with some projections indicating global sea level rise in excess of 1.0m (Rahmstorf, 2007). Phase 1 of the Gippsland Climate Change Study (McInnes et al., 2005a & b, 2006) and earlier work by CSIRO indicates that the major impacts of climate change to weather systems along the Gippsland coast include: · Increase dominance of south-westerly frontal synoptic weather patterns · Increase wind speed · Changed annual rainfall patterns · Increased storm surge height - up to 19% by 2070 · Increased frequency and intensity of extreme events by approx. 10%. Suggesting bigger storms … more often. This study - Phase 2 of the Gippsland Climate Change Study - has assessed coastal geological characteristics and erosion potential of the Gippsland coast from San Remo to Mallacoota, and based on climate change predictions, also determined the likely changes to coastal sediment transport patterns along the coast. Detailed wave modelling undertaken as part of this study is presented in Appendix 1. Assessment of coastal geology indicates that: · Approximately 78% of the Gippsland coast comprises highly erodible sediments (sandy beaches, sand dunes, colluvium, alluvium), and · Approximately 65% of the Gippsland coast comprises coastal dunes. Sea level rise will result in coastal recession as beaches equilibrate to the new wave and tidal regimes. The Bruun Rule provides a simplistic estimate of likely costal erosion due to sea level rise - for every 10cm of sea level rise, shoreline recession of 5-10m could be expected, depending on local wave conditions and sand dune characteristics. Hence shoreline recession of between 40m and 79m cam be expected along the Gippsland coast, based on 0.79cm sea level rise. Wave and sediment transport modelling undertaken for this study (Appendix 1) indicates, due to climate change-induced increased wind speeds, that there will be a significant increase in wave heights of up to 10% throughout the region, resulting in increased wave energy attacking the coast. In turn this results in:
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· Significant increases in total sediment mobility of 30% to 50% increase in gross sand transport along the Gippsland coast. · For locations west of Wilsons Promontory; typically higher seasonal variability to shoreline location, beach profiles and dune morphology (shape). · For locations east of Wilsons Promontory; higher seasonal variability to beaches, and significant increases in the net eastward transport of sand along the Gippsland coast, potentially resulting in accelerated erosion of sandy shorelines at the western end of beach cells and deposition towards the east against rocky headlands. The combined effect of sea level rise and changed sediment transport patterns is likely to result in significant erosion in many areas along the Gippsland coast. This will be further compounded by any lowering of the coastal land surface due to coastal subsidence. Hence, many assets, both built and natural, in close proximity to the shoreline are to varying extents considered at risk. The most vulnerable coastal sites are low-lying areas and/or those that have a high potential for erosion, and hence shoreline retreat. The most dramatic potential impact will result from the erosion and breaching of coastal dunes and barrier islands that currently protect inlets, estuaries, low-lying plains and wetlands located immediately behind the dunes and barrier islands, for example the Gippsland Lakes and Corner Inlet. A large variety of natural values and physical assets along the Gippsland coast are potentially at risk from climate change-induced sea level rise and coastal erosion. Response to climate change and sea level rise needs to be both pro-active, comprising increasing community awareness and planning for change, and re-active responses which involve either: · Doing nothing, · Retreating from impacted areas, · Adapting to (or accommodating) the change, or · Protecting (or defending) an area against the impact of the change. Many physical assets along the Gippsland coast can most likely be adequately and cost- effectively protected against the impacts of sea level rise, at least in the short to medium term. However, on a larger and far more complex scale, entire communities and dwellings may need to be relocated because the cost of protecting such areas from erosion and/or flooding is prohibitively high, particularly when on-going maintenance of protective measures is included. Some low-lying dwellings and coastal communities along the Gippsland coast may ultimately find that a managed relocation by retreating to higher ground is the only cost-effective long term response option. On-going protection measures such as dykes, levee banks, sea walls and pumps could be effective in the short term but would require considerable maintenance/replacement and upgrading over time. A vital component of adequate risk management involves being able to make balanced decisions regarding the most appropriate action, based on the magnitude of the risk, its consequences, the cost of taking action and the preparedness of the community to both pay for action and ‘forego private rights’. The key step towards being able to make informed and consistent decisions is for Government to provide clear policy direction regarding anticipated climate change and sea level rise impacts through proclaiming a statutory sea level rise and/or erosion setback, depicted as an overlay or development control in municipal planning schemes. Local Government will therefore need considerable support from State and Commonwealth Government to enable adequate
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10 REFERENCES AAMHatch, 2006 & 2007. Gippsland Ground Elevation Survey completed for Epochs 2 & 3, June 2004 to May 2007. Prepared for the Department of Primary Industries (Minerals and Petrolium Division). AGO, 2006a. Climate Change Impacts and Risk Assessment: A Guide for Government and Business. Australian Greenhouse Office. AGO, 1006b. Climate Change Scenarios for Initial Assessment of Risk in Accordance with Risk Assessment Guidance. Australian Greenhouse Office. AGO, 2007. Climate Change Adaptation Actions For Local Government. Report by SMEC Australia to the Australian Greenhouse Office, Department of the Environment and Water Resources, Commonwealth of Australia, 2007, ISBN: 978-921297-27-4 Bell, R., Hume, T, & Hicks, D, 2001. Planning for Climate Change Effects on Coastal Margins. Ministry for the Environment, Wellington, NZ. Bird, 1993. The Coast of Victoria. Melbourne University Press. Bird, E. C. F, 2002. Appendix 1 - In Gippsland Lakes Shore Erosion and Revegetation Strategy, Sjerp et al. 2002. Brooke, C. and Hennessy, K., 2005. Climate change impacts in Gippsland. Appendix 1 in Fisher, S. 2006, Climate Change Impacts and Adaptation in Gippsland. CSIRO Bureau of Meteorology, 2006. Australian Baseline Sea Level Monitoring Project: Annual Sea Level Data Summary Reports. National Tidal Centre, Bureau of Meteorology. Church, J. A. and White, N. J., 2006a. A 20th century acceleration in global sea level rise. Geophysical Research Letters. Vol. 33. Church J. A., Hunter, J. R., McInnes, K. L., & White, N. J., 2006b. Sea-level rise around the Australian coastline and the changing frequency of extreme sea-level events. Australian Meteorological Magazine, 55:4 CSIRO and Bureau of Meteorology, 2007. Climate Change in Australia – Technical Report 2007. www.climatechangeinaustralia.gov.au DSE, 2002. Victorian Greenhouse Strategy. Department of Sustainability and Environment. DSE, 2004a. Climate change in West Gippsland. Department of Sustainability and Environment. DSE, 2004b. Climate change in East Gippsland. Department of Sustainability and Environment. DSE, 2004c. Adapting to Climate Change: Enhancing Victoria's Capacity. Department of Sustainability and Environment. DSE, 2005. Victorian Greenhouse Strategy – Update. Department of Sustainability and Environment. DSE, 2006. Our Environment, Our Future - Sustainability Action Statement 2006. Department of Sustainability and Environment. EGCMA, 2006 East Gippsland Regional Catchment Strategy. East Gippsland Catchment Management Authority. Ethos NRM, 2008. Physical Impacts of Climate Change on the Gippsland Lakes - Workshop Discussion Prompts. Prepared for the Gippsland Lakes Task Force. Ethos NRM and Water Technology, 2008. Climate Change and Sea Level Rise Implications: Ninety Mile Beach and Lake Reeve – Honey Suckles to Paradise Beach. Prepared for Wellington Shire Council.
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Fisher, S., 2006. Climate Change Impacts and Adaptation in Gippsland. Part of the Regional Pilot Project Initiating Gippsland’s Response to Climate Change. West Gippsland Catchment Management Authority. Freij-Ayoub,R., Underschultz, J., Li, F., Trefry, C., Hennig, A., Otto, C., McInnes, K., 2007. Simulation of Coastal Subsidence and Storm Wave Inundation Risk in the Gippsland Basin. CSIRO. Garnaut, R., 2008. Garnaut Climate Change Review - Interim report to the Commonwealth, State and Territory Governments of Australia. GCB, 1999. Gippsland Lakes Coastal Action Plan. Gippsland Coastal Board. GCB, 2002. Gippsland Boating Coastal Action Plan. Gippsland Coastal Board. GCB, 2002. Integrated Coastal Planning for Gippsland - Coastal Action Plan. Gippsland Coastal Board. GCB, 2006. Gippsland Estuaries Coastal Action Plan. Gippsland Coastal Board. Gilmore, Wayne, pers. comm. West Gippsland Catchment Management Authority. Hansen, J., 2007. Scientific reticence and sea level rise. Environmental Research Letters, 2, 1-6. Hatton et al., 2004; Falling water levels in the Latrobe Aquifer – Gippsland Basin: Determination of Cause and Recommendations for Further work. CSIRO Hennessy et al., 2006. Climate Change Scenarios for Initial Assessment of Risk in Accordance with Risk Assessment Guidance. CSIRO IPCC, 2001 Third assessment on climate change. Intergovernmental Panel on Climate Change IPCC, 2007a. Climate Change 2007: The Physical Science Basis – Summary for Policy Makers. Fourth Assessment Report of the Intergovernmental Panel on Climate Change. IPCC, 2007b. Climate Change Impacts, Adaptation and Vulnerability Fourth Assessment Report of the Intergovernmental Panel on Climate Change. Lawson & Treloar Pty Ltd, and Loder and Bayly Consulting Group, 1996. Vulnerability of the Gippsland Lakes to climate change. Report # J5022/R1578 prepared for the Environment Protection Authority. McInnes et al., 2005a. Climate change in Eastern Victoria - Stage 1 Report: The effect of climate change on coastal wind and weather patterns. CSIRO McInnes et al., 2005b. Climate change in Eastern Victoria - Stage 2 Report: The effect of climate change on storm surges. CSIRO. McInnes et al., 2006. Climate change in Eastern Victoria - Stage 3 Report: The effect of climate change on extreme sea levels in Corner Inlet and the Gippsland Lakes. CSIRO. NATCLIM, 2007. Planning for Climate Change – A Case Study : City of Port Phillip. Pittock, B. ed, 2003. Climate Change: An Australian Guide to the Science and Potential Impacts. Australian Greenhouse Office, Canberra. Port of Melbourne Authority, 1992. Victorian coastal vulnerability study. Rahmstorf, S. 2007. A semi-empirical approach to projecting sea level rise. Science, Vol. 315. Riedel, P. and Sjerp, E., 2007. Erosion history of Ninety Mile Beach, Gippsland. Prepared for Parks Victoria. Sjerp et al., 2002. Gippsland Lakes Shore Erosion and Revegetation Strategy. Gippsland Coastal Board. Sjerp, E., 2002. Climate Change Implications for the Gippsland Coast – Presentation for Coastal Adaptation workshop, Altona, Victoria.
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SKM, 1995. Risk Analysis for Subsidence on the Gippsland Coast. Sinclair Knight Merz SKM 2001a, SKM 2001b. Sinclair Knight Merz studies commissioned by Minerals and Petroleum Division of the Department of Natural Resources and Environment - Possible range of subsidence near Golden Beach and near Yarram in Gippsland. SKM, 2006. Gippsland Lakes Second Entrance Study. Underschultz et al., 2006. Falling water levels in the Latrobe Aquifer – Gippsland Basin. CSIRO VCC, 2002. Victorian Coastal Strategy. Victorian Coastal Council. VCC, 2007. Draft Victorian Coastal Strategy. Victorian Coastal Council. Water Technology, 2007. Climate Change Wave Modelling - Sea Level Rise and Coastal Subsidence: Implications for the geomorphological aspects and associated physical and natural assets of the Gippsland coast. Prepared for Gippsland Coastal Board Water Technology & Ethos NRM, 2007. Discussion Paper - Sea Level Change and Costal Subsidence: Implications for geomorphological aspects and associated physical and natural assets of the Gippsland coast. Prepared for the Gippsland Coastal Board. WGCMA, 2005. West Gippsland Regional Catchment Strategy. West Gippsland Catchment Management Authority. Wheeler, P., 2008. Lakes Entrance Flood Visualisation. http://sahultime.monash.edu.au/LakesEntrance/ Whetton et al., 2002. Climate Change in Victoria: High Resolution Assessment of Climate Change Impacts. CSIRO
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11 Maps
11.1 Coastal Geology
11.2 Coastal Erosion Potential
11.3 Coastal Values and Threats - Environmental
11.4 Coastal Values and Threats - Infrastructure
11.5 Coastal Values and Threats – Cultural
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12 APPENDICES
12.1 Climate Change Wave Modelling
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