Report 3: Outer Barrier Coastal Erosion Hazard Gippsland Lakes/90 Mile Beach Local Coastal Hazard Assessment Project April 2014 Department of Environment and Primary Industries Gippsland Lakes/90 Mile Beach Coastal Hazard Assessment DOCUMENT STATUS Version Doc type Reviewed by Approved by Date issued v01 Draft Report Tim Womersley Andrew McCowan 06/09/2012 v04 Draft Report Tim Womersley Warwick Bishop 25/03/2013 v05 Draft Report Warwick Bishop Warwick Bishop 30/08/2013 v06 Draft Report Warwick Bishop Warwick Bishop 06/12/2013 v07 Final Final Report Warwick Bishop Warwick Bishop 14/04/2014 PROJECT DETAILS ippsland Lakes/90 Mile Beach Coastal Hazard Project Name Assessment Client Department of Environment and Primary Industries Client Project Manager Ashley Hall Water Technology Project Manager Warwick Bishop Report Authors Tim Womersley, Neville Rosengren, Josh Mawer Job Number 2363-01 Report Number R03 Document Name 2363-01R03v07_Coastal.docx Cover Photo: Outer Barrier at Bunga Arm (Neville Rosengren, 3 February 2013) Copyright Water Technology Pty Ltd has produced this document in accordance with instructions from Department of Environment and Primary Industries for their use only. The concepts and information contained in this document are the copyright of Water Technology Pty Ltd. Use or copying of this document in whole or in part without written permission of Water Technology Pty Ltd constitutes an infringement of copyright. Water Technology Pty Ltd does not warrant this document is definitive nor free from error and does not accept liability for any loss caused, or arising from, reliance upon the information provided herein. 15 Business Park Drive Notting Hill VIC 3168 Telephone (03) 8526 0800 Fax (03) 9558 9365 ACN No. 093 377 283 ABN No. 60 093 377 283 2363-01 / R03 v07 Final - 14/04/2014 ii Department of Environment and Primary Industries Gippsland Lakes/90 Mile Beach Coastal Hazard Assessment TABLE OF CONTENTS 1. Introduction .................................................................................................................. 1 2. Geomorphology ............................................................................................................. 2 2.1 Origin ....................................................................................................................................... 2 2.2 Coastal Barriers........................................................................................................................ 5 2.2.1 Gippsland Lakes Barrier Systems ............................................................................................. 6 2.2.2 Outer Barrier Geomorphology ................................................................................................ 8 2.2.3 Unit 1: Nooramunga Barrier Islands ...................................................................................... 11 2.2.4 Unit 2: New Entrance to Woodside Beach ............................................................................ 11 2.2.5 Unit 3: Woodside Beach to Glomar Beach ............................................................................ 14 2.2.6 Unit 4: Glomar Beach to Paradise Beach ............................................................................... 17 2.2.7 Unit 5: Paradise Beach to Loch Sport Ocean Beach .............................................................. 19 2.2.8 Unit 6: Loch Sport Ocean Beach to Ocean Grange ................................................................ 20 2.2.9 Unit 7: Bunga Arm ................................................................................................................. 22 2.2.10 Unit 8: Barrier Landing........................................................................................................... 23 2.2.11 Unit 9: Lakes Entrance ........................................................................................................... 24 2.2.12 Unit 10: Eastern Beach to Lake Bunga ................................................................................... 25 2.2.13 Unit 11: Lake Bunga to Red Bluff ........................................................................................... 25 2.3 Summary ................................................................................................................................ 26 3. MetOcean Conditions .................................................................................................. 28 3.1 Wind Climate ......................................................................................................................... 28 3.2 Wave Climate ........................................................................................................................ 28 3.2.1 Storm Wave Climate .............................................................................................................. 30 3.3 Coastal Water Levels ............................................................................................................. 34 3.3.1 Astronomical Tides ................................................................................................................ 34 3.3.2 Storm Surges.......................................................................................................................... 34 4. Coastal Dynamics and Geomorphological Changes ........................................................ 36 4.1 Sediment Budgets .................................................................................................................. 36 4.1.1 Nearshore Geology ................................................................................................................ 36 4.1.2 Sediment Sources and Sinks .................................................................................................. 38 4.2 Aeolian and Biological Processes and Dune Morphology ..................................................... 40 4.2.1 Incipient Foredunes ............................................................................................................... 40 4.2.2 Established Foredunes ........................................................................................................... 40 4.2.3 Foredune Vegetation ............................................................................................................. 40 4.2.4 Transgressive Dunes .............................................................................................................. 43 4.2.5 Climbing Dunes ...................................................................................................................... 44 4.2.6 Backscarp Sand Apron ........................................................................................................... 45 4.2.7 Elongate Blowout – Shore-Normal and Oblique ................................................................... 46 4.2.8 Shore-Parallel Depression Complex ...................................................................................... 48 4.3 Coastal Overwash .................................................................................................................. 50 4.3.1 Outer Barrier Washovers ....................................................................................................... 50 4.3.2 Reeves Beach to Seaspray ..................................................................................................... 51 2363-01 / R03 v07 Final - 14/04/2014 iii Department of Environment and Primary Industries Gippsland Lakes/90 Mile Beach Coastal Hazard Assessment 4.3.3 Ocean Grange ........................................................................................................................ 55 4.3.4 Bunga Arm ............................................................................................................................. 56 4.3.5 Eastern Beach ........................................................................................................................ 57 4.4 Longshore Transport and Contemporary Shoreline Change ................................................. 58 5. Response of Coastal Barriers to Rising Sea Levels .......................................................... 68 5.1 Overview ................................................................................................................................ 68 5.2 Barrier Erosion ....................................................................................................................... 71 5.2.1 Depth of Closure .................................................................................................................... 72 5.2.2 Dune and Berm Height .......................................................................................................... 72 5.2.3 Application of the Bruun Model at Representative Locations .............................................. 73 5.3 Barrier Translation ................................................................................................................. 80 5.3.1 Application of the Barrier Island Equilibrium Model at Representative Locations ............... 80 6. Short-Term Storm Related Erosion ............................................................................... 85 6.1 Assessment of Short Term, Storm Related Erosion ............................................................... 86 7. Evaluation of Sources of Uncertainty ............................................................................ 90 7.1.1 Barrier Translation and Overwash Processes