Kangaroo Island Coastal Hazard Strategy Kangaroo Island Coastal Hazard Strategy November 2018 Prepared for Kangaroo Island Council by Seed Consulting Services and Water Technology Kangaroo Island Coastal Hazard Strategy Kangaroo Island Coastal Hazard Strategy prepared for Kangaroo Island Council Prepared by: Seed Consulting Services 106 Gilles Street, Adelaide, South Australia 5000 P. +61 8 8232 4823 W. www.seedcs.com.au In collaboration with: Water Technology Cover photo: Nepean Bay. By Ross Evans Photography. Kangaroo Island Coastal Hazard Strategy Document Control Document information Information Document Owner Kangaroo Island Council Project ID 808 KI COAST Last Saved Date 22/03/2019 File Name DRAFT KI Coastal Hazard Strategy V2.2 Document history Version Issue date Version 1 1 November 2018 Version 2 20 November 2018 Version 2.1 25 November 2018 Version 2.2 1 March 2019 Document approvals Project Director Mark Siebentritt Authors Mark Siebentritt Disclaimer The information contained in this Seed Consulting Services (Seed) report is given in good faith and has been derived from sources believed to be reliable and accurate. Seed accepts no legal liability for the accuracy of field data, analytical results or mapping data provided as part of this report or for any associated loss in productivity, business or such like through third part use of this data. Seed accepts no legal liability for failure of third parties to obtain any necessary government or other agency permits or approvals with respect to any issue raised in this report where approvals may be required. The material and opinions in this report may include the views or recommendations of third parties, which may not necessarily reflect the views of Seed, or indicate Seed’s recommendation regarding a particular course of action. Seed does not provide advice of an investment or commercial valuation nature. Seed does not accept any liability for investment decisions made on the basis of environmental or other information provided in this report. Kangaroo Island Coastal Hazard Strategy Contents Executive summary ................................................................................................... i 1 Introduction ........................................................................................................ 1 1.1 Background ................................................................................................................................. 1 1.2 Objective ..................................................................................................................................... 2 1.3 How was this strategy developed?.............................................................................................. 2 2 Coastal hazard risk assessment ...................................................................... 5 2.1 Oceanographic and coastal processes ....................................................................................... 5 2.2 Erosion assessment .................................................................................................................... 6 2.2.1 Sandy shorelines ................................................................................................................................... 6 2.2.2 Estuaries, lagoons and tidal flats ........................................................................................................... 7 2.2.3 Soft rock ................................................................................................................................................ 7 2.2.4 Hard rock shoreline................................................................................................................................ 8 2.3 Inundation .................................................................................................................................... 8 2.4 Risk assessment definitions ........................................................................................................ 9 3 Potential impacts and response options ....................................................... 10 3.1 Overview ................................................................................................................................... 10 3.2 American River .......................................................................................................................... 11 3.2.1 Potential impacts ................................................................................................................................. 11 3.2.2 Response options ................................................................................................................................ 15 3.3 Antechamber Bay ...................................................................................................................... 18 3.3.1 Potential impacts ................................................................................................................................. 18 3.3.2 Response options ................................................................................................................................ 20 3.4 Baudin Beach ............................................................................................................................ 22 3.4.1 Potential impacts ................................................................................................................................. 22 3.4.2 Response options ................................................................................................................................ 23 3.5 Bay of Shoals ............................................................................................................................ 25 3.5.1 Potential impacts ................................................................................................................................. 25 3.5.2 Response options ................................................................................................................................ 28 3.6 Brownlow ................................................................................................................................... 29 3.6.1 Potential impacts ................................................................................................................................. 29 3.6.2 Response options ................................................................................................................................ 31 3.7 D’Estrees Bay............................................................................................................................ 34 3.7.1 Potential impacts ................................................................................................................................. 34 3.7.2 Response options ................................................................................................................................ 36 3.8 Emu Bay .................................................................................................................................... 37 3.8.1 Potential impacts ................................................................................................................................. 37 3.8.2 Response options ................................................................................................................................ 39 3.9 Kingscote ................................................................................................................................... 42 3.9.1 Potential impacts ................................................................................................................................. 42 3.9.2 Response options ................................................................................................................................ 44 3.10 Nepean Bay............................................................................................................................... 46 3.10.1 Potential impacts ............................................................................................................................. 46 3.10.2 Response options ............................................................................................................................ 49 Kangaroo Island Coastal Hazard Strategy 3.11 Penneshaw................................................................................................................................ 51 3.11.1 Potential impacts ............................................................................................................................. 51 3.11.2 Response options ............................................................................................................................ 53 3.12 Sapphire Town, Island Beach and Brown Beach...................................................................... 55 3.12.1 Potential impacts ............................................................................................................................. 55 3.12.2 Response options ............................................................................................................................ 56 4 Discussion ....................................................................................................... 58 4.1 Future impacts..........................................................................................................................