EIS 21390 ABO1 9611 Marine aggregate proposal Vol 1 - n - 14 :L £ OS 21390 I 552 UN EOMARINE 15 53 >7 ci2 P0 R TJA'________ 6Ao te14524Hd 40 31 jJ 4 4 CO 75 S G < Gpfl(210sec 3P 25 M IL 28 27 rT (Co ' I Lr 14 FS 37 46 ç5BnBuCkler 31 35 /8 54 23 14 SX oee B 32 43 GS IT$âii1ggregate 63 72 %ps ': 3jo2Ch 3 -.:: : o102/ 7/ flY/)a 72 '2 B 0 T A N Y4' 26 / ! .35 46 •. 46 2 BAY '27 62 73 74 54 ISO - i Baily 77 / L 7/ ZIj J2 4 ,rOr/ulI / :BATE04BAY ,g /7 )23 3 34 73 45OSborn S Sh S 77 f73 S S Sh '1;5 11 JjiIA i. ) 3 e 7,9 49 22 C 77 63 - 72 73 r 7 54 /L200L •/./ / - 64 1 73 lncrasuzg (ibOut .5½'(,n,uallv Mag. Varn. 12Th5'E. (/964) 22 14 Jtily....1993 S M 73 I F GEOMARINE I I I GEOMARINE P/L ACN 003 280 046 Consulting Coastal, Estuarine and Port Engineers I 81 Enmore Road, Enmore NSW 2042 ph:(02) 565 1377 fax:(02)565 1570 I LAWSON & TRELOAR PtyLtd ACN 001 882873 Coastal, Ocean and Port Consulting Engineers I 24/177-199 Pacific Highway, North Sydney NSW 2060 ph:(02) 922-2288 fax. (02) 922 1195 a A It Ri oil I Proposal 00fto H Coastal rocesses I I Volume 1 of 3 I Prepared for Metromix Pty Limited I GEOMARINE Report Number 50-002-RiO July, 1993 Published 1993 by WaveLength. Tress, a division of GEOMARINE P/L 81 Enmore Road ENMORE NSW 2042 Copyright © GEOMARINE P/L 1993 All intellectual property and copyright reserved. Apart from any fair dealing for the purpose of private study, research, criticism or review, as permitted under the Copyright Act, no part of this report may be reproduced by any process without written permission. This documentation was prepared for the purpose and exclu- sive use of METROMIX Pty Limited to accompany a Mining Lease application to the Department of Mineral Resources, NSW for approval to extract marine aggregate over areas described in the report and is not to be used for any other purpose or by any other persons or corporation. GEOMARINE P/L and LAWSON & TRELOAR Pty Ltd accept no responsibility for any loss or damage suffered howsoever arising to any third party, person or corporation who may use or rely on this report. No reliance should be placed on any data for any purpose other than for the purpose of this application for a Mining Lease. National Library of Australia Marine Aggregate Proposal Coastal Processes / A.F. Nielsen, D.B. Lord & P.D. Treloar. ISBN 0 646 09863 2 LAWSON & TRELOAR GEOMARINE I P Li Foreword I The studies reported herein were undertaken by GEOMARINE and LAWSON & TRELOAR on behalf of METROMIX to provide I advice to R W Corkery & Co for the preparation of an Environmental Impact Statement to the requirements of the Director of the Department of Planning; those requirements I are detailed in Appendix I. Pursuant to the Environmental Planning and Assessment I Regulation 1980 this report addresses, inter alia, the Director's requirements for the following specific matters: I • studies of the seabed and coastline conditions, prevailing wave and current climates, seabed bathymetry, to define implications for beach stability; 1 formulation of proposals for on-going environmental monitoring of effects on physical resources, processes I and pollution potential; identification of the likely effects of destabilisation or scouring of shipwrecks and the determination of I appropriate buffer zones; . assessment and modelling of likely impacts on coastal I geomorphology including sediment deposition, wave action and beach erosion. In respect of these studies Government consultation was un- I dertaken with the Public Works Department, Sydney Water Board, Department of Minerals and Energy, Maritime Services I Board and the National Parks and Wildlife Service. A F Nielsen GEOMARINE I 1 D B Lord 9 GEOMARINE I P D Treloar I LAWSON & TRELOAR I Forewort1 GEOMARINE LAWSON & TRELOAR Summary This report documents coastal processes studies relating to a proposal to extract marine aggregate from two areas on the inner continental shelf adjacent to Sydney. The northern area, extending offshore and across the ocean entrance to Botany Bay, lies adjacent to recreational beaches and the scientific marine research area at Cape Banks which has international significance as do the wetlands within Botany Bay. The south- ern area, offshore from the Royal National Park, lies adjacent to the popular recreational beaches at Marley and Wattamolla. Several shipwrecks are located adjacent to the proposed extrac- tion areas and are sites for recreational diving. The areas are fished commercially and are popular for recreational fishing. For these studies there existed an extensive field data set unparallelled for any investigation of this type anywhere in the world: The seabed north of Port Hacking Point, encompassing the Cape Banks application area, had been mapped thoroughly and precisely by the Public Works Department, NSW with sounder, side scan sonar and seismic methods and extensive surface sediment sampling. Detailed sediment coring had been undertaken also nearby by the Department of Mineral Resources. Additional sampling and coring within the proposed extraction area were undertaken for this project. The Providential Head area was mapped for this study with sounder and seismic surveys, and detailed surface sediment sampling and coring. The hydrodynamic data included continuous measurements of near seabed wave-induced and oceanic currents on the inner shelf off Sydney at sites in water depths of 24m (some 2 years), 60m and 80m (6 months), field observations of sand transport mechanisms at those sites, some 18 years of deepwater wave measurements offshore of Botany Bay, 12 months measurements of near surface and near bed oceanic currents at the Ocean Reference Station offshore at Bondi (and subsequent confirmation of these statistics with an additional 2 years of data) and long term wind data. These data were augmented with site specific current and wave measurements. The wave and current climates were defined using these measured data and numerical modelling techniques to extend these data bases. 60 Summanj LAWSON & TRELOAR GEOMARINE I n Li Detailed field descriptions of the adjacent beaches were made I and assessments of their variability were undertaken from detailed photogrammetric surveys produced from recent and historical vertical aerial photography. I Sediment transport assessments were made using field data and the latest computational techniques. A review of the international marine dredging and aggregate extraction experience, studies and regulations exemplified the I various effects that could arise from seabed extraction and indicated that in all areas studied where extraction is permit- I ted it could be undertaken safely beyond 30m water depths. The criterion adopted for the design of the extraction plans was I that there should be no measurable change to the existing shoreline environment; specifically, the unconsolidated shore- lines comprising the beaches, the entrances to the estuaries I and the rocky reef communities. No change was defined as where calculated changes were an order of magnitude smaller than the equivalent natural variations as well as not being I measureable in the field using standard techniques. This led to the development of constraints on extraction that were I adopted in the design of the proposed extraction plans. Specif- ically, these constraints were that extraction be limited to: I a 5m below present seabed levels; a beyond the 35m isobath off beaches; and I a beyond the 25m isobath off the cuffed coastline. The analyses demonstrated that extraction as proposed would I not change the shoreline wave climates or sand transporting processes or result in erosion or realignment of adjacent beaches. The rates of sand transport in the areas proposed for I extraction were assessed to be very small. While there would be some slight changes to these transport rates in the extracted areas such changes would be negligible and insignificant. That I the time over which the extracted depressions would fill in from the surrounding seabed areas was calculated to be millennia indicated that, for all intents and purposes, the extracted I depressions would remain stable. Programmes for necessary additional studies, management 1 practices and monitoring procedures have been outlined. I Summaiy NO GEOMARINE LAWSON & TRELOAR Contents Volume 1 I Foreword (i) Summary (ii) Preface and Acknowledgments (ix) I Units and Abbreviations (x) 1 Introduction 1 1 1.1 Description of Proposal .......................1 1.2 Study Aims and Objectives ....................3 1.3 Study Methods, Consultation and Reporting ...... 3 1.3.1 Case Studies Review ...........................3 1.3.2 Definition of the Existing Environment .............3 1.3.3 Constraints Assessment .........................4 1.3.4 Assessment of Impacts ..........................4 1.3.5 Consultation ..................................4 1.3.6 Reporting .................................... 5 1.4 Investigation Team .......................... 5 1.4.1 Introduction ................................... 5 1.4.2GEOMARINE ............................... 5 1.4.3 LAWSON & TRELOAR .......................6 1.4.4 HYDROGRAPHIC SURVEYS .................6 1.4.5 SOUTHERN AERIAL SURVEYS ...............6 2 Case Studies 7 2.1 Introduction ................................7 2.2 Projects ....................................9 2.2.1 Botany Bay, N.S.W.............................9 2.2.2 Kirra Beach, Qid. .............................. 9 2.2.3 Kochi Coast, Japan ............................. 9 2.2.4 Genkai Sea, Japan .............................. 9 2.2.5 United Kingdom .............................. 10 2.2.6 USA ....................................... 10 2.3 Analytical and Field Studies .................. 10 2.3.1 Introduction .................................. 10 2.3.2 United Kingdom .............................. 11 2.3.3 France ...................................... 11 2.3.4 Japan ....................................... 11 2.3.5 The Netherlands .............................. 11 2.3.6 New Zealand ................................. 11 2.4 Regulations ................................11 2.5Summary .................................. 12 64 Contents LAWSON & TRELOAR GEOMARINE I I 1 3 Physiographic Setting 13 3.1 Introduction ..............................