Rivoli Bay Study
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WATTLE RANGE COUNCIL Rivoli Bay Study 301015-03541 – 001 26 Oct 2015 Infrastructure Level 12, 141 Walker Street, North Sydney NSW 2060 Australia Telephone: +61 2 8923-6866 Facsimile: +61 2 8923-6877 www.worleyparsons.com ABN 61 001 279 812 © Copyright 2015 WorleyParsons Services Pty Ltd WATTLE RANGE COUNCIL RIVOLI BAY STUDY SYNOPSIS This study reviews the current management plans, assesses the success and failure of existing stabilisation measures along the beach, compiles and examines all the latest information with respect to technical surveys of the beach compartments at Rivoli Bay and details short, medium and long term strategies to address the erosion threat at Beachport Jetty and the foreshore north of the Lake Frome outlet. Disclaimer This report has been prepared on behalf of and for the exclusive use of Wattle Range Council, and is subject to and issued in accordance with the agreement between Wattle Range 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 Wattle Range Council and WorleyParsons is not permitted. PROJECT 301015-03541 - RIVOLI BAY STUDY REV DESCRIPTION ORIG REVIEW WORLEY- DATE CLIENT DATE PARSONS APPROVAL APPROVAL A Issued for internal 7-Jul-14 N/A review C Adamantidis A Nielsen A Nielsen B Draft 26-Sep-14 C Adamantidis A Nielsen A Nielsen C Final Draft 13-Feb-15 C Adamantidis A Nielsen A Nielsen D Draft Final 26-May-15 C Adamantidis A Nielsen A Nielsen E Final 26 Oct 15 C Adamantidis A Nielsen A Nielsen c:\users\chris.adamantidis\documents\projects\03541 lake george rivoli bay\for submission\rev e final\report_anz ln review caa reve.doc Document No : 001 Page ii WATTLE RANGE COUNCIL RIVOLI BAY STUDY CONTENTS EXECUTIVE SUMMARY.................................................................................................................... 1 Community Consultation ............................................................................................................... 2 Coastal Processes ........................................................................................................................ 3 Climate Change ............................................................................................................................ 4 Assessment of Coastal Structures ................................................................................................ 4 Preliminary Coastal Management Scheme ................................................................................... 5 1 INTRODUCTION ................................................................................................................ 7 1.1 Background ......................................................................................................................... 7 1.2 Stakeholder and Community Consultation ......................................................................... 8 2 COASTAL PROCESSES .................................................................................................. 10 2.1 Introduction ....................................................................................................................... 10 2.2 Regional coastal processes .............................................................................................. 10 2.2.1 Cross-shore sediment transport ........................................................................... 11 2.2.2 Sediment Budget.................................................................................................. 11 2.3 Local coastal processes ................................................................................................... 16 2.3.1 Beachport ............................................................................................................. 16 2.3.2 Southend .............................................................................................................. 17 2.3.3 Sediment Sampling .............................................................................................. 21 2.3.4 Beach erosion, recession and coastal inundation ............................................... 25 2.3.5 Climate Change ................................................................................................... 34 2.3.6 Coastal Inundation ............................................................................................... 41 2.3.7 Wave Climate and Storms ................................................................................... 43 2.3.8 Beach profile changes at Beachport .................................................................... 44 3 ASSESSMENT OF EXISTING COASTAL STRUCTURES .............................................. 48 3.1 Introduction ....................................................................................................................... 48 3.1.1 Documented Structure Features .......................................................................... 49 3.1.2 Failure Mechanisms ............................................................................................. 50 c:\users\chris.adamantidis\documents\projects\03541 lake george rivoli bay\for submission\rev e final\report_anz ln review caa reve.doc Page 1 301015-03541 : 001 Rev E : 26 Oct 2015 WATTLE RANGE COUNCIL RIVOLI BAY STUDY 3.2 Conditions during the field inspection ............................................................................... 50 3.3 Summary ........................................................................................................................... 50 4 QUANTITATIVE ASSESSMENT ...................................................................................... 52 4.1 Methodology ..................................................................................................................... 52 4.2 Wave Modelling ................................................................................................................ 53 4.2.1 Model Results ...................................................................................................... 53 4.3 SBEACH Modelling ........................................................................................................... 55 4.3.1 Results ................................................................................................................. 55 4.4 Hydraulic Armour Stability of Rock groynes and revetments ........................................... 56 4.4.1 Rock Armour Stability .......................................................................................... 56 4.4.2 Temporary Geotextile Container Revetment – Beachport ................................... 60 4.4.3 Summary .............................................................................................................. 61 4.5 Layout of Groyne Schema ................................................................................................ 62 4.6 Analysis of Historical Aerial Photography ......................................................................... 65 4.6.1 Beachport ............................................................................................................. 65 4.6.2 Southend .............................................................................................................. 70 4.7 Crest Levels of seawalls and frontal dunes ...................................................................... 72 4.7.1 Wave Runup and overtopping ............................................................................. 72 4.7.2 Scour Potential ..................................................................................................... 77 4.8 Climate Change ................................................................................................................ 77 4.8.1 Effect of Climate Change on Beachport and Southend seawalls ........................ 79 4.9 Summary ........................................................................................................................... 81 5 PRELIMINARY MANAGEMENT SCHEME ...................................................................... 82 5.1 Main coastal management issues .................................................................................... 82 5.2 Preliminary Coastal Management Options ....................................................................... 83 5.3 Option 1 - Extension of groynes at channel outlet to Lake George .................................. 84 5.3.1 Longshore Sediment Transport and Outlet Stability ............................................ 85 5.4 Option 2 – Improve layout of groynes and provision of additional groyne at Beachport .. 88 c:\users\chris.adamantidis\documents\projects\03541 lake george rivoli bay\for submission\rev e final\report_anz ln review caa reve.doc Page 2 301015-03541 : 001 Rev E : 26 Oct 2015 WATTLE RANGE COUNCIL RIVOLI BAY STUDY 5.5 Option 3 - Provision of upgraded seawall at jetty ............................................................. 88 5.5.1 Rigid Gravity Structures ....................................................................................... 91 5.5.2 Rigid Sloping Revetments .................................................................................... 92 5.5.3 Semi-Rigid Sloping Pattern-Placed Unit revetments ........................................... 93 5.5.4 Flexible Near-Vertical Mass Gravity Structures ..................................................