PUBLIC WORKS DEPARTMENT, N.S.w. I ENGINEERING DIVISION I I I I HAWKESBURY RIVER HYDRAULIC AND I SEDIMENT TRANSPORT PROCESSES REPORT NO.2 I I I TIDAL GAUGING OF THE HAWKESBURY RIVER: I 23-24 OCTOBER, 1984 I I I I I M. N. CLARKE M. G. GEARY CHIEF ENGINEER PRINCIPAL ENGINEER I PUBLIC WORKS DEPARTMENT RIVERS AND PORTS BRANCH I DECEMBER 1987 I Report No. PWD 87059 I ISBN 724029494 I I I I POBEWORD I The estuaries of NSW are an abundant source of renewable biological resources and non-renewable construction materials. Most major population centres are located on estuaries and while the waterways provide the main I outlet for water orientated recreation, they also cope with sewage, industrial effluent, urban silt and stormwater runoff, as well as I fertilizer and pesticide enriched runoff from agricultural lands. Estuaries are complex systems with hydrodynamic, sedimentary, chemical and biological processes Which react, often synergistically, to artificial disturbance. Community demand for estuarine resources requires that I priority be placed on understanding estuarine processes so that future management will be capable of maximising the benefits of estuaries without I jeopardising their ecological viability. The Hawkesbury River is the longest estuary in NSW and one of the most heav ily exploited. The Hawkesbury Valley holds all of Sydney's gravel I resources and 80t of construction and industrial sand, about 2800 hectares of very productive agricultural land is irrigated from the tidal waterway, it is the State's third largest oyster producer, the waterway is a major tour ist attraction and it' provides the only water-based recreation I convenient to the expanding western area of Sydney. It also sustains extensive wetlands which provide important wildlife habitats. I Problems are already evident with recurring poor water quality, widespread river bank erosion , severe flooding and competing demands for waterway development. Despite these signs of stress, demand on the waterway is I escalating; as much as 400 million cubic metres of sand and gravel reserves are needed to satisfy the metropolitan demand over the next 50 years, the population of the Hawkesbury/Nepean catchment is expected to double to 1.2 million by the year 2020. The latter will strain the nutrient assimilation I ,and dispersion capability of the estuary as well as intensify competing demands for recreation and habitat conservation. I 'Models of the hydrodynamic and sedimentary processes of the Hawkesbury River are needed so that the individual and cumulative impact of developnent proposals can be predicted and future developnent planned to I avoid adverse effects. The Department has prepared a reference set of reports covering the hydraulic and sediment processes data currently available on the Hawkesbury River. This document is one of the volumes in that set which collectively prov ide a foundation for future model I studies. Collation of this data set is merely the first step in what will be a long I endeavour if the Hawkesbury River is to be fully understood and appreciated and the amenity and resources of this magnificent waterway are to be I sustained for the benefit and enjoyment of future generations. I I I I I I I (ii) TABLE OF CONTENTS I Page No. I Foreword (i) Table of Contents (ii) List of Tables (iii) I List of Figures (iv) List of Definitions (vi) I Summary (vii) 1. Introduction 1 I 2. Weather 2 3. Freshwater Flow 4 I 4. Datum 7 I 5. Water Levels 11 6. References 13 I 7, Acknowledgements 13 Appendix A : Temporary Automatic Tide Recorders - I Equipment and Operational Details 14 Appendix B Tidal Gradients for the Hawkesbury River between Wisemans Ferry and Windsor I 20th December 1983 15 Appendix C : Level of Tideboard Zero for Automatic Recorders 16 I Photographs 1 and 2 I, Figures 1 to 34 Figures Bl to B3 I I I I I I I I ( iii) LIST OF TABLES I Page No. Table 2.1 General Weather at Richmond M.O. 2 I Table 2.2 Richmond M. O. - Daily Rainfall Figures 3 Table 2.3 Surface Synoptic Charts at 1000 HRS EST 3 I Table 3.1 Freshwater Discharges for the Gauging Stations 5 I Table 3.2 Discharge at Penrith - NepeanRiver 5 Table 4.1 Levels of Tideboards 8 I Table 4.2 Levels of Temporary Bench Marks 8 Table 4.3 Levels of Bench Marks ""9 I Table 4.4 Comparison of Datums 10 Table 5.1 Fort Denison Tide Predictions I 11 Table 5.2 Summary of Tidal Lags 12 Table A1 Temporary Automatic Tide Recorders located 14 I in the Hawkesbury Valley I I I I I I I I I I I I I (iv) LIST OF FIGURES I Figure 1 Location of Tideboards and Automatic Recorders I Figure 2 Location of Tideboards for Richmond and Colo Sites Figure 3 Comparison of Water Levels - Hawkesbury River I 23/24 October 1984 Figure 4 Comparison of Water Levels - Lower Hawkesbury Estuary 23/24 October 1984 I Figure 5 Comparison of Water Levels - Mangrove Creek 23/24 October 1984 I Figure 6 Comparison of Water Levels - MacDonald River 23/24 October 1984 I Figure 7 Comparison of Water Levels - Colo River 23/24 October 1984 Figure 8 Tidal Gradients in the Hawkesbury River, 23 October I 1984 - Flood Tide Flow at the Ocean Figure 9 Tidal Gradients in the Hawkesbury River, 23/24 I ,October 1984 - Ebb Tide Flow at the Ocean Figure 10 Tidal Gradients in Mangrove Creek, 23 October 1984 - I Flood Tide Flow Figure 11 Tidal Gradients in Mangrove Creek, 23 October 1984 - I Ebb Tide Flow Figure 12, Tidal Gradients in the MacDonald River, 23 October I 1984 - Flood Tide Flow Figure 13 Tidal Gradients in the MacDonald River, 23/24 I October 1984 - Ebb Tide Flow Figure 14 Tidal Gradients in the Colo River, 23 October 1984 - Flood Tide Flow I Figure 15 Tidal Gradients in the Colo River, 23/24 October 1984 - Ebb Tide Flow I Figure 16 Water Levels 23/24 October 1984 - Tideboard 1 I Figure 17 Water Levels 23/24 October 1984 - Tideboard 2 Figure 18 Water Levels 23/24 October 1984 Tideboard 3 I Figure 19 Water Levels 23/24 October 1984 - Tideboard 4 Figure 20 Water Levels 23/24 October 1984 - Tibeboard 5 I Figure 21 Water Levels 23/24 October 1984 - Tideboard 6 I I I I (v) Figure 22 Water Levels 23/24 October 1984 - Fort Denison Gauge I Figure 23 Water Levels 23/24 October 1984 - Fitness Camp Tide Recorder I Figure 24 Water Levels 23/24 October 1984 - Bobbin Head Tide Recorder I Figure 25 Water Levels 23/24 October 1984 - Peats Ferry Bridge Tide Recorder Figure 26 Water Levels 23/24 October 1984 - Mooney Mooney Tide I Recorder Figure 27 Water Levels 23/24 October 1984 - Private Tide I Recorder at Spencer Figure 28 Water Levels 23/24 October 1984 - Lower Mangrove I Tide Recorder Figure 29 Water Levels 23/24 October 1984 - Central MacDonald I Tide Recorder Figure 30 Water Levels 23/24 October 1984 - Colo Tide Recorder I Figure 31 Water Levels. 23/24 October 1984 - Windsor Tide Recorder I Figure 32 Water Levels 23/24 October 1984 - North Richmond Tide Recorder Figure 33 Water Levels 23/24 October 1984 - Webbs Creek Flood I Recorder "Figure 34 Water Levels 23/24 October 1984 - Freemans Reach I Flood Re corder Figure B1 Comparison of Water Levels - Hawkesbury River, 20 I December 1983 Figure B2 Tidal Gradients in the Hawkesbury River, 20 December I 1983 - Flood Tide Flow Figure B3 Tidal Gradients in the Hawkesbury River, 20 December I 1983 - Ebb Tide Flow I I I I I I I (vi) LIST OF DEFINITIONS I Bund - Temporary artificial embankment constructed across a watercourse. I Ebb Tide - The occurrence of falling water surface of a tide Ebb Current - The seaward movements of water along a tidal channel I Flood Tide - The occurrence of rising water surface of a tide I Flood Current - The landward movement of water along a tidal channel Left/Right Bank - The bank to the left/right of an observer looking I downstream Thalweg - In hydraulics, the line joining the deepest points of an inlet or stream channel I Instantaneous Tidal Gradient - ·The water level along a tidal channel at an instant I in time. Tidal Period - The interval of time between two consecutive like I phases of the tide. I I I I I I I I I I I I I ( vii) SUMMARY I Tidal data was collected at the Hawkesbury River and its major tributaries on the 23rd and 24th October, 1984. I . Manual reading of tide boards located near the tidal limit of the Hawkesbury River, Colo River, MacDonald River and Mangrove Creek were taken to augment data collected on automatic tide recorders installed for several months. The objective of all these tidal measurements was I the preparation of comprehensive tidal gradients for the river. The manual water level readings carried out at 6 tide board I locations measured the following tidal ranges: I Location Tidal Range (m) Ebb Flood I 1st 2nd TB1 Agnes Banks 0.06 0.08 0.09 I TB2 North Richmond 0.29 0.33 0.33 TB3 Upper Colo (upstream) 0.01 0.03 0.03 TB4 Upper Colo (downstream) 0.98 1.09 1.09 -I TB5 MacDonald River 0.35 0.44 0.45 TB6 Mangrove Creek 0.93 1.04 1.04 I Automatic recorders at thirteen other locations in the river (including the Fort Denison gauge) recorded the following tidal I ranges: Type of Recorder Location Tidal Range (m) ·1 (T = Tide, F = Flood)- Ebb Flood I Fort Denison 1.42 1.67 1.56 T Fitness Camp 1.42 1.67 1.53 T Bobbin Head 1.48 1.75 1.67 I T Peats Ferry 1.48 1.71 1.59 T Mooney Mooney 1.52 1.66 1.65 T Lower Mangrove 1.56 1.75 1.70 I T Spencer 1.52 1.74 1.63 T Central MacDonald 1.19 1.31 1.31 T Colo 1.34 1.47 1.44 I T Windsor 1.07 1.15 1.13 T North Richmond 0.26 0.28 0.28 F Webbs Creek 1.61 1.80 1.73 I F Freemans Reach 0.26 0.30 0.30 it T = Temporary tide recorders used to measure river tides for I several months.