City of Victor Harbor
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City of Victor Harbor Victor Harbor Coastal Management Study FINAL REPORT December 2013 Project Team Geoff Fisher- AWE Doug Bowers-AWE Doug Lord-Coastal Environment Pty Ltd Nicky O’Broin-AWE Nicole Ross-AWE City of Victor Harbor AWE Document History and Status Issue Version Issued to Qty Date Reviewed Approved Draft V3 CVH 1 7/6/13 DB GF Final Draft V4 CVH 1 2/8/13 GF GF Prelim Final V5 CVH 1 23/10/13 NOB GF Council V6 CVH 1 4/12/13 GF GF Endorsed Printed: December 4, 2013 Last Saved: December 4, 2013 File Name: 13123 Final Report_v6.1_131204.doc Project Manager: Doug Bowers/Geoff Fisher Client: City of Victor Harbor Project: Victor Harbor Coastal Management Study Name of Document: Final Document Version: V6 Job Number: 13123 Council Endorsement Details: Resolution No. is OC 13/0514, dated Monday 25 November 2013. OC 13/0514 Victor Harbor Coastal Management Study Moved: Cr B Bond Seconded: Cr T Telfer 1. That the Coastal Management Study as presented be adopted by Council to guide future works and funding applications for the Victor Harbor Coastline. 2. That the 30 year expenditure forecast be incorporated into Council’s Draft 10 Year Capital Works Program at its next review. CARRIED 13123, Victor Harbor Coastal Management Study i AWE City of Victor Harbor ii 13123, Victor Harbor Coastal Management Study AWE City of Victor Harbor Table of Contents Executive Summary 1 Scope of Assessment ................................................................................................................................... 1 2 Existing Context ........................................................................................................................................... 3 2.1 Regional Setting ................................................................................................................................ 3 2.2 Aboriginal & European Heritage ....................................................................................................... 3 2.3 Planning and Development ............................................................................................................... 5 2.4 Geological and Geo-morphological Background ............................................................................ 10 2.5 Inman River ..................................................................................................................................... 13 2.6 Vegetation ...................................................................................................................................... 14 2.7 Recorded Changes to the Beach and Coast .................................................................................... 14 2.8 Infrastructure .................................................................................................................................. 19 3 Coastal Processes ...................................................................................................................................... 22 3.1 Past Studies of the Coast ................................................................................................................ 22 3.2 Tides ................................................................................................................................................ 23 3.3 Winds .............................................................................................................................................. 23 3.4 Waves ............................................................................................................................................. 24 3.5 Inman River ..................................................................................................................................... 25 3.6 Storm Surge .................................................................................................................................... 26 3.7 Bathymetric and Survey Data ......................................................................................................... 26 3.8 Climate Change Impacts ................................................................................................................. 27 4 Project Site Impacts and Key Issues .......................................................................................................... 28 4.1 Variability in Alongshore Sand Supply ............................................................................................ 28 4.2 Coastal Erosion and Recession........................................................................................................ 31 4.3 Stormwater Discharge and Seagrass Impacts ................................................................................. 35 4.4 Inman River Impacts ....................................................................................................................... 35 4.5 Seagrass Accumulation ................................................................................................................... 36 4.6 Native Vegetation ........................................................................................................................... 36 4.7 Current and Future Hazards and Risks to Address ......................................................................... 37 4.8 Natural Resource Assets ................................................................................................................. 37 5 Community Consultation ........................................................................................................................... 38 5.1 Consultation Activities .................................................................................................................... 38 5.2 Community Feedback ..................................................................................................................... 39 5.3 Future Community Consultation .................................................................................................... 41 6 Risk Assessment ........................................................................................................................................ 42 6.1 Risk Assessment Process ................................................................................................................. 42 6.2 Assets at Risk .................................................................................................................................. 42 6.3 Summary of Risks (without any intervention) ................................................................................ 44 6.4 Triggers for Intervention ................................................................................................................. 45 7 Management Options ............................................................................................................................... 47 iii 13123, Victor Harbor Coastal Management Study City of Victor Harbor AWE 7.1 Consideration of Management Techniques .................................................................................... 47 7.2 Approach......................................................................................................................................... 51 7.3 Engineering Intervention Options .................................................................................................. 52 7.4 Asset Management Options ........................................................................................................... 53 7.5 Planning Responses ........................................................................................................................ 54 7.6 Funding Arrangements ................................................................................................................... 55 7.7 Indicative Unit Costs for Major Capital Work Items ....................................................................... 55 8 Conclusions and Recommendations ......................................................................................................... 56 8.1 Overview ......................................................................................................................................... 56 8.2 Conclusions ..................................................................................................................................... 56 8.3 Recommendations .......................................................................................................................... 57 9 References ................................................................................................................................................. 58 List of Tables Table 2-1 Aerial Photography Summary ............................................................................................................... 15 Table 2-2 Survey Profile Locations ........................................................................................................................ 17 Table 3-1 Tide Levels For Victor Harbor ............................................................................................................... 23 Table 3-2 Winds .................................................................................................................................................... 23 Table 7-1 Consideration of Structural Management Options - Shore Parallel Structures .................................... 47 Table 7-2 Consideration of Structural Management