I rn .FI-rZH E-N . "1 Department of Public Works NSW I I Chipping Norton Lake Scheme I Hydraulic Investigation Report No 270 April 1980 I I I )1 :1 I I I 'I I I I I 1 1 I I I I t I I I I CHIPPING NORTON FEBRUARY 1978 I ( Phot09raphy by Qosco Ply. Ltd. ) 'I I I Department of Public Works, N.S.W. I MANLY HYDRAULICS LABORATORY I I CHIPPING NORTON LAKE SCHEME I HYDRAULIC INVESTICATION I I I I I I I I I I I I A.T. Webb I P. Spurway Report No. 270 1980 I April I I I SUMMARY Dredging of the Georges River at Ch1pping Norton has been a I major source of clean bU1lding sand for some years. Further dredging and assoc1ated works will eventually convert the area 1nto a recreational lake. I A scaled hydraul1c model was used in conJunct10n with f1eld data collection and hand calculations to determine various aspects of the behaviour of the proposed lake scheme. The following problems assoc1ated I with creation of the scheme were considered : • continuously stagnant cond1tions in a tidal cycle in any area could I allow the accumulation of noxious debr1s. Inadequate m1xing of any pollutants enter1ng the lake. result1ng from insuff1cient c1rculation 1n the lake. could also be possible. I • strat1ficat10n of waters in the lake could lead to nOX10US conditions due to deoxygenat10n of the deep layers. I • the silt and sand load 1n the r1ver would tend to settle in the lake. with assoc1ated siltation problems in the upstream reaches a I possib111ty. • the large volumes of silt present in ponds could eventually be incorporated 1nto the lake scheme. Eros10n of the existing layer of fines could be a source of pollution downstream of the completed lake I scheme. • proposed beaches in the lake scheme should be constructed to min1- I mise sand losses from wave and current action. An investigation 1nto the above problems was carr1ed out by the I Hydrau11cs Laboratory of the Department of Public Works for the Chipping Norton Project Sect10n of the Department. I From the invest1gation. the follow1ng conclus10ns were reached: I • a lake conf1gurat10n is recommended that ensures adequate tidal flushing. and promotes mix1ng of pollutants. 1n all areas of the lake I scheme. • strat1f1cation at depth may prove to be a problem. and regular monitoring of salinity and temperature is recommended. No solut10ns I to the problem are proposed at this stage. • no s1ltat10n problems in the lake are foreseen provided no dramatic I changes 1n the river's sed1ment load occur. I 1 I I I sediment presently in dredged ponds will slowly erode in tidal • conditions. More rapid removal will occur during minor floods and I freshes. Fines transported from the upper areas of the catchment will ensure the continuation of turbidity In the Georges River. • beaches can be constructed to minimise sand losses under waves and I currents. Appropriate profiles are provided. I I I I I I I I I I I I I I I ii I I I I CONTENTS Page No. I Summary (i) Contents ( iii) List of Appendices (v) I List of Figures (vi) LlSt of Plates (viii) Definition of Symbols ( ix) I 1. Introduction 1 1.1 The Problems 1 I 1.2 Investigations 2 2. Model Investigation 4 2.1 The Model 4 I 2.2 Model Results-Circulation and Current Patterns 9 2.3 Recommendations 13 3. Pollutants 14 I 3.1 Introduction 14 3.2 Parameters Used to Measure Pollution 14 3.3 Levels and Trends 14 I 3.4 Pollutant Sources 17 3.5 Effects of Lake Scheme on the Movement and Dispersion of Pollutants 19 I 3.6 Conclusion 20 4. Stratification 21 4.1 The Problem of Stratification 21 I 4.2 Conditions for Stratification 21 4.3 Application to Present Situation 22 4.4 Effect of Lake Scheme 23 I 4.5 Recommendations 23 5. Sedimentation 24 5.1 Suspended Sediment 24 I 5.2 Sand Transport 28 6. Movement of EXisting Bed Fines 30 I 6.1 Characteristics of the Fines 30 6.2 Critical Shear 30 6.3 Available Bed Shear in Tidal Flow 31 I 6.4 Conclusions 31 7. Stability of Beaches 32 7.1 Introduction 32 I 7.2 Stability of the Foreshore Slope 32 7.3 Stability of the Offshore Slope 33 7.4 Depth of Beach Toe 34 I 7.5 Level of Back of Beach 36 7.6 Recommendations 37 I iii I I I I 8. Conclusions 38 9. Recommendations 39 I 10. References 40 I I I I I I I I I I I I I I I iv I I I I LIST OF APPENDICES I Appendix A Equa tions of Motion and the Model Relations I Appendix B Model Scales and Model Capabilities Appendix C Equipment Details I Appendix D Measures of Pollution I Appendix E Beach Stab111ty Calculations I I I I I I I I I I I I v I I I I LIST OF FIGURES_:- I 1. Plan of Chipping Norton Lake (1977) I 2. Chipping Norton Model Plan - Configuration 1 3. ChiPPing Norton Lake Model - Layout of EqUipment I 4. Results of Model Verification 5. Simulation of Tidal Flow I 6. Configuration 1 Flood tide circulation patterns I 7. Conf 19ura tl0n 1 Ebb tide circulation patterns 8. Conf igura tion 2 Flood tide circulation patterns I 9. Conf igura tion 2 Ebb tide circulation patterns 10. Conf igura tlon 3 Flood tide circulation patterns I 11. Configuration 3 Ebb tide circulation patterns I 12. Configuration 4 Flood tide circulation patterns 13. Configuration 4 Ebb tide circulation patterns I 14. Configuration 5 Flood tide circulation patterns 15. Configuration 5 Ebb tide circulation patterns I 16. Conf igur a tlon 6 Flood tide circulation patterns 17. Configuration 6 Ebb tide circulation patterns I 18. Details of Recommended Lake Configuration (overlay on Fig.l) I 19. Water Quality Parameters (A, B and C) 20. Seasonal Dependence of Dissolved Oxygen I 21. Coliform - Time Relation 22. Rainfall vs Faecal Coliform I 23. Faecal Coliforms - Seasonal Trends I 24. Rainfall vs Turbidity 25. Ebb Flow Tidal Excursions I VI I I • I I 26. Flood Flow TIdal ExcursIons 27. Tidal Residuals I 28. Bed SedIment GradIng Curve - Bed FInes in ChippIng Norton Lake 29. Laboratory Set-up for Shear Tests I 30. Bed FInes - Areas of Movement under Mean Tidal Flow 31. Bed Fines - Areas of Movement under Peak TIdal Flow I 32. Position of Proposed Beaches I 33. Sand DIameter - Slope RelatIonship of Beaches 34. ShIelds Diagram for PredIctIon of Sediment MotIon I 35. Recommended Beach ProfIles (A and B) 36. Depthwise VarIatIon of Velocity I 37. Flow Patterns I 38. ElectronIc Details for Photographics 39. Comparison Between Velocity Profiles for Waves and Currents I 40. Velocity Components for CombIned Currents and Wave Action I I I I I I I I vIi I I I I LIST OF PLATES I I Frontispiece Aerial view of ChIpping Norton. February 1978 I (photography by QASCO Pty. Ltd.) Flow patterns I 1. Ebb Tide - Tidal SImulation 2. Ebb TIde - 'Start-up' Test I 3. Flood Tide - Tidal Simulation I 4. Flood Tide - 'Start-up' Test 5. Low Water Level I 6. HIgh Water Level 7. Flow 45 mils (Prototype) I 8. Flow 90 mils (Prototype) I 9. Unroughened Bed 10. Roughened Bed I 11. Ebb Tide - with Prospect Creek 12. Ebb TIde - without Prospect Creek I 13. Flood Tide - with Prospect Creek I 14. Flood Tide - without Prospect Creek 15. Configuration 6 - Flood TIde 16. ConfIguration 6 - Ebb Tide I , 17. Configuration 6 - Flood TIde (Prospect Creek end of model) I 18. ConfIguration 6 - Ebb Tide (Prospect Creek end of Model) 19. Dye Tracing Flood Tide Sequence I 20. Dye TraCIng Ebb Tide Sequence I viii I I I I DEFINITION OF SYMBOLS I The following symbols are used throughout the report. Subscripts are defined where they appear. I ao horizontal water particle displacement under waves near the bed e base of natural logarithm I fw friction factor under waves (Appendix E) I fwc friction factor under waves and currents (Appendix E) g gravitational acceleration I h water depth l,j,k refer to coordinate directions x,y,z (Appendices A and B) I k kinematic energy of turbulence (Appendices A and B) I k wave number (= 2n/L) (Appendix E) I mixing length of turbulence I n model distortion factor p pressure (Appendices A and B) I r bed roughness (as equivalent sand grain diameter) t I u,v horizontal velocity components I w vertical velocity component x,y horizontal cartesian coordinates I z vertical cartesian coordinate c Chezy roughness coefficient I D median grain size I E estuary number ~ Froude number I H wave height I ix I I I K eddy viscos1ty coefficient I K* eddy V1SCOS1ty coefficient, 1ncorporating shear effects L wavelength I p t1dal pr1Sm Q flow I IR Reynolds number of flow I T period U hor1zontal water particle velocity under waves (Appendix E) I U* shear veloc1ty v veloc1ty of steady current (Append1x E) I z vert1cal d1stance from bed (Appendix E) I r spec1f1c we1ght I) thickness of viscous sublayer 11 vertical displacement of water surface from mean surface I elevation at Z=O I K von Karman's constant V k1nematic viscosity of water I p dens1ty 't shear stress I cp wave phase angle III wave angular frequency (= 2rr/T) I 9 non d1mensional Shields parameter I I I I I x I I I I 1.