GREATER TAREE CITY COUNCIL Black Head to Crowdy Head Coastline Hazard Definition Study Volume 1: Report 301017-00051 September 2010 8-14 Telford Street Newcastle East NSW 2300 Australia Tel: +61 2 4907 5300 Fax: +61 2 4907 5333 www.worleyparsons.com WorleyParsons Services Pty Ltd ABN 61 001 279 812 © Copyright 2010 WorleyParsons Services Pty Ltd GREATER TAREE CITY COUNCIL BLACK HEAD TO CROWDY HEAD COASTLINE HAZARD DEFINITION STUDY VOLUME 1: REPORT Disclaimer This report has been prepared on behalf of and for the exclusive use of Greater Taree City Council, and is subject to and issued in accordance with the agreement between Greater Taree City Council and WorleyParsons. WorleyParsons accepts no liability or responsibility whatsoever for it in respect of any use of or reliance upon this report by any third party. Copying this report without the permission of Greater Taree City Council or WorleyParsons is not permitted. PROJECT 301017-00051 - BLACK HEAD TO CROWDY HEAD HAZARD DEFINITION STUDY REV DESCRIPTION ORIG REVIEW WORLEY- DATE CLIENT DATE PARSONS APPROVAL APPROVAL A Issued for internal review N/A 3 Jul 09 N/A N Patterson D Messiter B Draft Issued for review 5-Aug-09 N/A N/A N Patterson D Messiter N/A C Final 17 Sept 10 D Messiter H Nelson D Messiter Page ii GREATER TAREE CITY COUNCIL BLACK HEAD TO CROWDY HEAD COASTLINE HAZARD DEFINITION STUDY VOLUME 1: REPORT CONTENTS 1. INTRODUCTION ................................................................................................................1 1.1 Background.........................................................................................................................1 1.2 Coastline Management Process.........................................................................................1 1.3 Scope of this Report ...........................................................................................................2 2. STUDY AREA.....................................................................................................................4 2.1 Site Description...................................................................................................................4 2.2 Historical Setting.................................................................................................................5 2.2.1 General ..................................................................................................................5 2.2.2 Sand Mining ...........................................................................................................7 3. DATA AQUISITION.............................................................................................................8 3.1 Previous Studies/ Literature Review...................................................................................8 3.1.1 General ..................................................................................................................8 3.1.2 Racecourse Creek ...............................................................................................10 3.1.3 Diamond Beach Coastal Erosion Study...............................................................11 3.2 Review of Historical Aerial Photographs ..........................................................................11 3.3 Photogrammetry ...............................................................................................................12 3.4 Survey Data ......................................................................................................................12 4. COASTAL PROCESSES..................................................................................................13 4.1 Wave Climate....................................................................................................................13 4.2 Elevated Water Levels......................................................................................................16 4.3 Wave Runup .....................................................................................................................17 4.4 Coastal Storms .................................................................................................................19 4.4.1 General ................................................................................................................19 4.4.2 Storm Types.........................................................................................................20 4.4.3 Storm History .......................................................................................................21 4.4.4 Storminess Indicator ............................................................................................23 Page iii 301017-00051 : Rev C September 2010 GREATER TAREE CITY COUNCIL BLACK HEAD TO CROWDY HEAD COASTLINE HAZARD DEFINITION STUDY VOLUME 1: REPORT 4.5 Wave Induced Currents ....................................................................................................25 4.5.1 Wave Model .........................................................................................................26 4.6 Short Term Onshore/Offshore Sediment Transport – Storm Demand .............................27 4.6.1 General ................................................................................................................27 4.6.2 Storm Demand.....................................................................................................28 4.6.3 Estimate of Storm Demand..................................................................................29 4.7 Longer Term Sand Movement ..........................................................................................29 4.7.1 General ................................................................................................................29 4.7.2 Previous Assessments of Longer Term Sand Movement ...................................30 4.7.3 Interpretation of most recent DECCW Photogrammetry .....................................32 4.8 Geotechnical Conditions...................................................................................................39 4.8.1 Onshore sediments..............................................................................................39 4.8.2 Offshore sediments..............................................................................................41 4.9 Climate Change ................................................................................................................41 4.9.1 Sea Level Rise.....................................................................................................41 4.9.2 Other Climatic Change Considerations ...............................................................43 4.10 Aeolian (Wind) Sand Movement ..................................................................................43 4.11 River Entrances............................................................................................................44 4.11.1 Farquhar Inlet.......................................................................................................44 4.11.2 Harrington Entrance.............................................................................................48 4.12 Regional Processes – Conceptual Model ....................................................................49 5. COASTLINE HAZARD ASSESSMENT............................................................................59 5.1 Overview ...........................................................................................................................59 5.2 Beach Erosion Hazard......................................................................................................59 5.3 Shoreline Recession Hazard ............................................................................................60 5.3.1 Long Term Recession Due to Net Sediment Loss...............................................61 5.3.2 Long Term Recession Due to Sea Level Rise.....................................................62 5.3.3 Discounting of Historical Recession Rates ..........................................................65 Page iv 301017-00051 : Rev C September 2010 GREATER TAREE CITY COUNCIL BLACK HEAD TO CROWDY HEAD COASTLINE HAZARD DEFINITION STUDY VOLUME 1: REPORT 5.4 Sand Drift Hazard .............................................................................................................66 5.5 Coastal Inundation Hazard ...............................................................................................67 5.6 Stormwater Erosion Hazard..............................................................................................69 5.7 Climate Change ................................................................................................................70 5.8 Slope and Cliff Instability Hazard......................................................................................70 6. DEFINITION OF COASTLINE HAZARD ZONES.............................................................72 7. CONCLUSION..................................................................................................................75 7.1 Beach Erosion and Shoreline Recession .........................................................................75 7.2 Coastal Inundation............................................................................................................81 7.3 Stormwater Erosion ..........................................................................................................82