21.4.1 - January 2020 COASTAL VULNERABILITY ASSESSMENT Whitemark, Flinders Island CLIENT Flinders Island Council Dock4 Architects October 2018 1 Geo-Environmental Solutions 29 Kirksway Place, Battery Pont. Ph 6223 1839 Fax 6223 4539 21.4.1 - January 2020 Executive Summary ............................................................................................................................................ v List of Abbreviations ......................................................................................................................................... vii 1 Introduction ............................................................................................................................................... 1 2 Objectives .................................................................................................................................................. 1 3 Site Details ................................................................................................................................................. 1 3.1 Project Area Land Title ............................................................................................................................. 1 3.2 Project Area Regional Coastal Setting ...................................................................................................... 3 4 Planning ..................................................................................................................................................... 6 4.1 Australian Building Code Board................................................................................................................ 6 4.2 State Coastal Policy .................................................................................................................................. 6 4.3 Building Act 2000 ..................................................................................................................................... 6 4.4 Interim Planning Scheme Overlays ........................................................................................................... 7 4.5 Flinders Island Council Planning Scheme .................................................................................................. 7 4.6 Coastal Hazards Technical Report ............................................................................................................ 7 4.7 Proposed Development ............................................................................................................................ 7 5 Physical Site Assessment ............................................................................................................................ 8 5.1 Geology .................................................................................................................................................... 8 5.2 Project Area Geomorphology ................................................................................................................... 8 5.3 Bathymetry ............................................................................................................................................. 16 5.4 Shoreline Geometry ................................................................................................................................ 18 5.5 Beach Classification ................................................................................................................................ 19 5.5.1 Reflective ........................................................................................................................................... 19 5.5.2 Beach Plus Tidal Sand Flat .................................................................................................................. 19 5.5.3 Low Tide Terrace ................................................................................................................................ 19 5.5.4 Summary ............................................................................................................................................ 19 5.6 Coastal Erosion Overview ....................................................................................................................... 19 5.7 Previous Studies ..................................................................................................................................... 21 6 Stillwater Inundation Assessment ............................................................................................................ 23 6.1 Previous Studies ..................................................................................................................................... 23 6.2 Site Baseline Seawater Levels ................................................................................................................. 23 6.2.1 Storm Tide.......................................................................................................................................... 23 6.2.2 Sea Level Rise ..................................................................................................................................... 23 6.2.3 Wind Setup ........................................................................................................................................ 24 6.2.4 Stillwater Levels ................................................................................................................................. 24 7 Coastline Hydrodynamics ......................................................................................................................... 24 7.1 Methods ................................................................................................................................................. 25 7.1.1 Swell Waves ....................................................................................................................................... 25 7.1.2 Wind Waves ....................................................................................................................................... 25 7.1.3 Wave Attenuation .............................................................................................................................. 25 7.1.4 Wave Inundation ............................................................................................................................... 25 7.2 Findings .................................................................................................................................................. 26 7.2.1 Significant Swell Waves ..................................................................................................................... 26 7.2.2 Localised Wind Waves ....................................................................................................................... 27 © Geo-Environmental Solutions Pty Ltd i 2 21.4.1 - January 2020 7.2.3 Wave Conditions ................................................................................................................................ 28 7.2.4 Dominant Wave Characteristics ........................................................................................................ 28 7.2.5 Wave Attenuation from Sea Bed Friction & Breaker Zone Hydrodynamics ...................................... 29 7.2.6 Wave Runup and Wave Setup ........................................................................................................... 30 8 Coastline Inundation Levels ...................................................................................................................... 30 8.1 Site 1 ....................................................................................................................................................... 30 8.2 Site 5 ....................................................................................................................................................... 31 9 Sediment Erosion Assessment .................................................................................................................. 32 9.1 Previous Studies ..................................................................................................................................... 32 9.2 Scope of Works ....................................................................................................................................... 32 9.3 Historical Aerial Imagery ........................................................................................................................ 32 9.3.1 Site 1 .................................................................................................................................................. 33 9.3.2 Site 2 .................................................................................................................................................. 33 9.3.3 Site 4 .................................................................................................................................................. 33 9.3.4 Site 5 .................................................................................................................................................. 33 9.4 Tidal Prism Analysis ................................................................................................................................ 34 9.5 Nalinga Creek Erosion ...........................................................................................................................