Dee Why Lagoon Data Compilation Study Draft Report MHL845 . January 1997 I I I I I I I I I I I I I 'I I I DEE WHY LAGOON DATA COMPILATION STUDY I I I I ~'I I I Department of Public Works and Services I Manly Hydraulics Laboratory I Draft Report MHL845, January 1997 I DPWS Report No. 97004, ISBN 0 7310 6882 3 I I I I I I I Foreword I The Dee Why Lagoon Data CompIlatlOn Study was carned out by Manly Hydrauhcs Laboratory (MHL) for Warnngah CouncIl The study was undertaken and report prepared by LOUIse Howells and Heather Nelson under the supervIslOn of Doug Lord and revIewed by I Steve Wylhe ThIs report was prepared wIth assIstance m provIdmg mformatlOn from a number of sources I mc1udmg Damel Lovett, Enca GnffIths, Jenme Powell and Mark Evens (Warnngah CouncIl) and RIchard MIchelle and Annabelle ReIder (Fnends of Dee Why Lagoon) I ThIS study was Jomtly funded by Warnngah CouncIl and the Department of Land and Water ConservatlOn (DLWC) under the Estuary Management Program. I I I I I I I I I I I DRAFT MHL845 - i I 28 January, 1997 I I I I Summary The New South Wales Estuary Management Pohcy was developed to encourage the I mtegrated, balanced, responsible and ecologically sustamable use of the State's estuanes The pohcy IS designed to reflect and promote cooperatIOn between the State Government, local government, catchment management comrruttees, landholders and estuary users m the I development and ImplementatIOn of estuary management plans for each estuary I To asSiSt m the development of estuary management plans, an Estuary Management Manual (NSW Government 1992) was pubhshed to outhne the processes of ImplementatIOn I Essentially, the process consIsts of eIght steps. These steps are (1) form an estuary management comrruttee; (2) assess eXlstmg data (data compilatlon study); I (3) carry out estuary processes study, (4) carry out estuary management study, (5) draft estuary management plan, I (6) review estuary management plan, (7) adopt and Implement estuary management plan, and I (8) momtor and review management process The Estuary Management Committee was formed m 1994 and Manly Hydrauhcs Laboratory was commIssioned by Warnngah CouncIl to undertake the second stage of the estuary I management process for Dee Why Lagoon Data was compiled from a number of sources for this study (outlmed m SectIOn 2 of the I report) A vrulable data IS presented under subject headmgs mcludmg hIStOry, legislatIOn and pohcy framework, catchment charactenstlcs, chmate, geology and geomorphology, water mflow and outflow, entrance behaVIOur and management, water quahty, ecology and I recreation (SectIOns 3-12). From avrulable data a hst of slgmficant events was compIled (SectIOn 13) I A prehmmary assessment of the mam processes IS presented (SectIOn 14) whIch hlghhghts the data gaps for the lagoon whIch need to be addressed to move to the next step of the estuary I management process - the estuary process study The compIled mformatlOn IS presented m two forms one m alphabetical hstmg by author I (AppendIx A) and the other hstmg by subject (Appendix B) I I DRAFT MHL845 - u I 28 January, 1997 I I I I I Table of Contents 1. Introduction 1 I 1 1 Study Objectives 1 1 2 Study Methodology 1 I 1 3 Report OutlIne 1 2. Liaison 2 3. History 3 I 4. Legislation and Policy Framework 6 5. Catchment Characteristics 9 6. Climate 10 I 61 Ramfall 10 6 2 Temperature and HumIdIty 10 6 3 W md Speed and DIrectIOn 10 I 6 4 Solar RadIatIOn 11 6 5 EvaporatIOn 11 7. Geology and Geomorphology 12 I 7 1 GeologIcal Settmg 12 7 2 GeomorphologIcal Settmg 12 7 3 Catchment SOIl Landscapes 13 I 7 4 Lagoon SedIments 16 7 5 SedImentatIon 16 76 Dredgmg 17 I 8. Water Inflow and Outflow 18 8 1 Lagoon Water Level 18 82 Inflows 18 I 8 2 1 DIrect Ramfall 18 8 2 2 Stormwater Dramage and Overland Flows 18 8 2 3 Sewer Overflows 19 I 8 2 4 Groundwater Inflow 19 8 2 5 TIdal Inflow 20 I 8 2 6 Barner Overtoppmg by Ocean 20 827 Floodmg 20 83 Outflows 20 I 8 3 1 EvaporatIOn 20 8 3 2 Groundwater Outflow 20 8 3 3 Lagoon 'Breakout' 21 I 9. Entrance Behaviour and Management 22 9 1 Entrance HydraulIcs 22 9 I 10pemng 22 I 912 Closmg 23 9 2 Entrance Management PolIcy and LegIslatIOn 24 93 Entrance Management Works 25 I 9 4 Impacts of Lagoon Openmg 25 DRAFT MHL845 - ui I 28 January, 1997 I I I 9.4.1 Water Level for Blfdhfe 25 9.4.2 Odour Problems 25 I 9 4 3 Fish Habitat 26 10. Water Quality 27 10 1 Physical 28 I 10 2 Chemical 29 10 3 BIOlogical 30 11. Ecology 32 I 11 1 Flora 32 11 2 Fauna 33 I 11 2.1 Fish 33 12. Recreation 48 13. Significant Events 49 I 14. Processes and Data Gaps 51 15. References 53 I Appendices Appendix A Alphabetical Database I Appendix B Database by Subject I I I I I I I I I I DRAFT MHL845 - iv I 28 January,1997 I I I I List of Tables 1 AerIal Photographs DLWC Sector Sydney Heads 46 I 2 AerIal Photographs DLWC Sector' Mona Vale' 45 3 Monthly Mean Pan Evaporation Data 4 GeologIcal Umt DeSCrIptIOns I 5 SoIl Umts 6 FIsh SpecIes IdentIfIed (Vertebrates) 7 Molluscs (Invertebrates) I 8 AnnelIds (Invertebrates) 9 Crustaceans (Invertebrates) 10 Insects (Invertebrates) I 11 BIrd SpecIes 12 Events I List of Figures I 1 LocatIOn Plan 2 Catchment and Topography 3 Catchment Zonmg I 4 RaInfall Trends for the RegIOn 5 Wmd Rose - Summer 6 Wmd Rose - Autumn I 7 Wmd Rose - Wmter 8 Wmd Rose - SprIng 9 Geology of RegIOn I 10 EstuarIne ClassIfIcatIOn 11 Salme Coastal Lake EvolutIOn 12 Bathymetry (to be provIded by Sydney Water) I 13 SoIl Landscape of the Catchment 14 SedIment SamplIng LocatIOns 15 Transect A-A I 16 Transect B-B 17 Transect C-C I 18 Surface Water Levels and Runoff 19 MHL Water Level StatIOn Data 20 SedIments Basms I 21 Catchment Overflows and Groundwater Bores 22 NatIOnal Trust ClassIfIcatIOn (1981) I I I DRAFT MHL845 - v I 28 January, 1997 I I I I I 1. Introduction I Dee Why Lagoon IS located on Sydney's northern beaches and draInS a catchment area of approximately 550 ha (FlgUlc I). The lagoon IS one of four coastal lagoons In the area of I varyIng sizes that are all Intermittently open to the sea 1.1 Study Objectives I The study objectives are to Identify, compile and review eXistIng data pertInent to Dee Why Lagoon As compamons to thiS report, an Issues Paper and DISCUSSion Paper have been I prepared from the findmgs of thiS report 1.2 Study Methodology I The lagoon has been the subject of a number of studies which have been compiled for thiS report Over 130 Items IncludIng documents, maps and photographs were Identified as beIng relevant to the lagoon These Items were Identified from a number of sources listed In SectIOn I 2 and the findIngs of the review reported here The Items located are catalogued In two formats In the Appendices AppendiX A contaInS an alphabetical listIng (by author) of the Items and AppendiX B contaInS a listIng by subject Eighteen fields were Identified for Items I to be categonsed These are outlined and descnbed In the Appendices Items were also subjectively assessed for their usefulness and rated on a scale of 1-5. I 1.3 Report Outline I The report IS diVided mto a number of sectIOns With four maIn themes. SectIOn 2 outlmes the liaison for the IdentificatIOn of data I SectIOns 3-12 compile and review the most relevant data and cover every aspect of InformatIOn available for the lagoon IncludIng hiStOry, legislation and policy framework, I catchment charactenstIcs, climate, geology and geomorphology, water Inflow and outflow, entrance behaVIOur and management, water quality, ecology and recreatIOn I SectIOn 13 proVides a summary of slgmficant events denved from the reviewed data SectIOn 14 outlines a prelimInary assessment of the processes and the maIn Issues for the I lagoon to Indicate the data gaps requIrIng attentIOn pnor to undertaking the estuary process study I I DRAFT MHL845 - 1 I 28 January, 1997 I I I I I 2. Liaison Data collatIOn mvolved contactmg relevant Government departments, agencies, non­ I government organISatIOns and mdlvlduals as listed below I • Australian Museum • A WT Environmental Measurement Services • Bureau of Meteorology I • Coastal Environment Centre • Colman, Phil • Dee Why Library I • Department of EnVIronment, Sport and Terntones (Federal) • Department of Mmeral Resources Library I • DLWC Bndge St Library • DLWC Estuary Management • DLWC Coastal Management I • DPWS InfonnatIOn Resource UnIt • EPA Library • Kay, Stephen I • Lennox,Sue • Macquane Umverslty Library • Manly HydraulIcs Laboratory Library, Files and Data I • Maxwell, Nonna • NPWS Library • NSW Flshenes Research InstItute I • RTA Technology Library Services • State Library of New South Wales - General Reference Library I • State Library of New South Wales - Mitchell Library • Sydney Water Library • Total EnVironment Centre I • Umverslty of New South Wales Library • Warnngah Council • Water Data Services, DLWC I • Water Reference Library (UNSW) I I I DRAFT MHL845 - 2 I 28 January, 1997 I I I I 3. History A detaIled history pertment to the lagoon and Its surrounds can be found m the geology thesIs I by Vogt (1994) The followmg sectIOn IS a summary of the hlstoncal sectIOn of that report I Vogt (1994) dates possible discovery of the lagoon to the earliest European settlement m 1788 when Governor Arthur Phillip and a small group travelled north m search of water and I sUitable farmmg land Other expeditions followed The ongmal mhabltants of the area are Identified as the KunnggaI Abongmes who were I forced off their traditional land and placed m reserves James Meehan, the Government Surveyor dunng 1814, was the first person to make wntten reference to the lagoon whilst surveYIng land for possible fanmng grants The lagoon did not I make for good fannIng land and thus a full survey was not completed In a revIsit to the area In 1815 IS the first record of the namIng, 'DY Beach'.