BROOKLYN ESTUARY PROCESS STUDY (VOLUME I OF II) by Water Research Laboratory Manly Hydraulics Laboratory The Ecology Lab Coastal and Marine Geosciences The Centre for Research on Ecological Impacts of Coastal Cities Edited by B M Miller and D Van Senden Technical Report 2002/20 June 2002 (Issued October 2003) THE UNIVERSITY OF NEW SOUTH WALES SCHOOL OF CIVIL AND ENVIRONMENTAL ENGINEERING WATER RESEARCH LABORATORY BROOKLYN ESTUARY PROCESS STUDY WRL Technical Report 2002/20 June 2002 by Water Research Laboratory Manly Hydraulics Laboratory The Ecology Lab Coastal and Marine Geosciences The Centre for Research on Ecological Impacts of Coastal Cities Edited by B M Miller D Van Senden (Issued October 2003) - i - Water Research Laboratory School of Civil and Environmental Engineering Technical Report No 2002/20 University of New South Wales ABN 57 195 873 179 Report Status Final King Street Date of Issue October 2003 Manly Vale NSW 2093 Australia Telephone: +61 (2) 9949 4488 WRL Project No. 00758 Facsimile: +61 (2) 9949 4188 Project Manager B M Miller Title BROOKLYN ESTUARY PROCESS STUDY Editor(s) B M Miller, D Van Senden Client Name Hornsby Shire Council Client Address PO Box 37 296 Pacific Highway HORNSBY NSW 1630 Client Contact Jacqui Grove Client Reference Major Involvement by: Brett Miller (WRL), David van Senden (MHL), William Glamore (WRL), Ainslie Fraser (WRL), Matt Chadwick (WRL), Peggy O'Donnell (TEL), Michele Widdowson (MHL), Bronson McPherson (MHL), Sophie Diller (TEL), Charmaine Bennett (TEL), John Hudson (CMG), Theresa Lasiak (CEICC) and Tony Underwood (CEICC). The work reported herein was carried out at the Water Research Laboratory, School of Civil and Environmental Engineering, University of New South Wales, acting on behalf of the client. Information published in this report is available for general release only with permission of the Director, Water Research Laboratory, and the client. - ii - TABLE OF CONTENTS 1. EXECUTIVE SUMMARY .......................................................................................... 1 1.1 Background.............................................................................................................. 1 1.2 Objectives and Scope .............................................................................................. 1 1.3 Relevant Findings.................................................................................................... 2 2. INTRODUCTION ........................................................................................................ 8 2.1 Background.............................................................................................................. 8 2.2 Study Area............................................................................................................... 8 2.3 Study Team.............................................................................................................. 9 2.4 Report Structure....................................................................................................... 9 3. CATCHMENT CHARACTERISTICS.................................................................... 11 3.1 Catchment Description.......................................................................................... 11 3.2 Climate .................................................................................................................. 12 3.2.1 Rainfall.................................................................................................... 13 3.2.2 Temperature and Humidity ..................................................................... 13 3.2.3 Wind ........................................................................................................ 14 3.2.4 Evaporation ............................................................................................. 14 3.2.5 Solar Radiation........................................................................................ 15 3.3 Catchment Land Use ............................................................................................. 15 3.4 Catchment Runoff................................................................................................. 17 3.4.1 Urban and Rural Runoff ............................................................................... 17 3.4.1.1 Nutrient Loadings......................................................................17 3.4.1.2 HSPF Model Results................................................................. 19 3.4.2 Road and Rail Runoff................................................................................... 20 3.4.3 Point Sources of Pollution............................................................................ 22 3.5 Fluvial Sedimentation............................................................................................ 23 3.5.1 Sources of Fluvial Sedimentation ........................................................... 23 3.5.2 Sedimentation Rates................................................................................ 24 3.6 Sewage Disposal.................................................................................................... 26 3.6.1 Brooklyn and Dangar Island......................................................................... 26 3.6.2 Mooney Mooney, Cheero Point and Little Wobby ...................................... 28 3.6.3 Vessel Discharges......................................................................................... 29 3.7 Stormwater Management....................................................................................... 30 3.8 Groundwater.......................................................................................................... 31 3.9 Hawkesbury-Nepean River................................................................................... 31 4. HYDRODYNAMICS AND FLUSHING.................................................................. 33 4.1 Review of Literature.............................................................................................. 33 4.2 Methods of Hydrodynamic Assessment................................................................ 35 4.2.1 Tidal Gauging Exercise October 2001 ......................................................... 35 4.2.2 RMA Modelling ........................................................................................... 35 4.3 Water Level Variability......................................................................................... 36 4.3.1 Astronomic Tides ......................................................................................... 37 4.3.2 Low Frequency Sea Level Oscillations........................................................ 38 4.3.3 Wind Setup ................................................................................................... 38 4.3.4 Fresh Water Inputs ....................................................................................... 39 4.3.5 Tidal Prism ................................................................................................... 39 4.3.6 Current Velocities......................................................................................... 40 - iii - 4.4 Water Exchange and Flushing............................................................................... 41 4.4.1 Circulation .................................................................................................... 41 4.4.2 Model Estimates of Flushing Times............................................................. 42 4.4.3 Stratification ................................................................................................. 43 4.4.4 Mixing Plot and Flushing in Mooney Mooney Creek.................................. 44 4.4.5 Particle Tracking .......................................................................................... 45 4.5 Sedimentation of Navigation Channels................................................................. 47 4.6 Summary................................................................................................................ 50 5. WATER AND SEDIMENT QUALITY ................................................................... 51 5.1 Water Quality Data................................................................................................ 51 5.1.1 Review of Literature..................................................................................... 51 5.1.2 Available Water Quality Data ...................................................................... 53 5.1.3 Additional Data Collection........................................................................... 53 5.1.4 Data Limitations ........................................................................................... 54 5.2 Analysis of Water Quality Data ............................................................................ 54 5.2.1 Comparison to Water Quality Guidelines .................................................... 54 5.2.2 Spatial and Temporal Trends........................................................................ 59 5.3 Sediment Quality................................................................................................... 60 5.3.1. Overview ................................................................................................. 60 5.3.2 Methods.................................................................................................. 61 5.3.3 Core Locations .......................................................................................