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. I ntrodu ction In the Chlpping Norton area of the Georges Rlver (Flgure 1), extractl0n of sand deposlts over many years has resulted in an increase in I water surface to more than 100 hectares. The Chipplng Norton Lake Authorlty lS managing the remalnlng extraction operatl0ns and carrying out other works so that the area is developed lnto a recreational lake, which I would also lnclude a wlldllfe preservatl0n area. The lnltially proposed shape (Flgure 2) of the lake, baslcally as proposed ln the Cox and Corkill report (ref.1)., lnvolved enlarglng the I open area and dredglng to a depth of 8 metres.
Before major amounts of money were expended, lt was considered I necessary to study certain aspects of the hydraullc behaviour of the lake. The followlng description of the problems was lncluded in the brief from I the Chipplng Norton Project Sectlon dated April 27th, 1978. 1.1 The Problems
I 1.1.1 Circulatlon and Current Patterns
To avoid stagnatl0n or pollution problems, the clrculatl0n of I water in the lake after constructl0n must be determlned with respect to the varlOUS flow condltions which may occur. It must be ensured that the proposed configuratlon permits adequate circulatl0n and that no areas which could stagnate exist. If any such areas are shown by the study to exist, I these must be examined and the lake configuration adjusted, lf possible, to remove their presence.
I 1.1.2 Distribution of Pollutants
There are sewerage treatment works adJoinlng the Georges Rlver, I which dlscharge effluents into the Georges River upstream of the lake. It is expected that, because of nutrients, the lake may have conslderable algae or weed growth problems particularly in shallow or poorly flushed areas. Assessment of retention of nutrlents or other pollutants is I necessary to permit determinatlon of remedlal act lon, if any, required. I 1.1.3 Stratiflcation Effects In the deeper water of the lake, stratlflcatl0n may result and de-oxygenatlon may lead to noxious conditions. The possiblilty of these I conditions eXlstlng and thelr solutions must be lnvestigated. 1.1.4 Sedimentatl0n Effects
I The lake may cause settlement of suspended materlal carr led by the river. The possible sediment movement within the lake must therefore I be determined and areas where siltation may occur located. • References are listed on pages 40-43.
I 1 I I I Expected amounts of sand transported during floods must also be determined to evaluate the necess1ty of ma1ntenance dredging.
I 1.1.5 Movement of EX1sting Bed Fines
The present approved method of operation of extract10n of sand I 1S 1n enclosed ponds. This method has resulted in large volumes of silt and clay eX1st1ng on the bed of these ponds. Removal of the foreshore str1p to construct th1s lake may release these fines into the ma1n stream I of the Georges River or pick them up dur1ng floods and carry and deposit them downstream of the lake. An assessment as to the behav10ur of these fines must be made, as they could eventually cause considerable pollut10n problems downstream of the lake. The behav10ur of these f1nes may have a I bear1ng on the extent of the foreshore str1p or road remnants which are left within the lake area. I 1.1.6 Stab1l1ty of Beaches Early in 1979, the study was extended to include the problems I of beach stab1l1ty. For the proposed beaches 1n the lake, the stab1l1ty of beach slopes needs to be exam1ned and the l1ke11hood of sand movement should be I determined. Since this is beyond the capab1lities of the model, analyt1cal pred1ctions must be carr1ed out. I 1.2 Invest1gations 1.2.1 Circulat10n and Current Patterns
I A hydraulic model of the area was used to ident1fy areas of stagnat10n or low flows, as well as give est1mates of velocities 1n the main flow area under normal tidal flows. The model had a vert1cal scale of I 50 and a horizontal scale of 250. I 1.2.2 D1str1but10n of Pollutants Data collected by the State Pollution Control Commission was used to gauge the present level of pollutants. The hydraulic model results I were used to obta1n an estimate of the retention of these pollutants. 1.2.3 Stratif1cat10n Effects I F1eld investigations were used to check for the possib1l1ty of strat1fication. An assessment of the stabi11ty of possibly stratified layers was made using published techniques.
I 1.2.4 Sed1mentation Effects
The potential for sedimentation was checked uS1ng field I observations and hand analysis. I 1.2.5 Movement of Exist1ng Bed Fines An estimate of the possible movement of f1nes was made using
I 2 I I I the f1eld observations, laboratory tests of shear res1stance and est1mates of bed shear obtained from the model tests.
I 1.2.6 Stabil1ty of Beaches
Results from field 1nvestigation of beach slopes in areas with I s1milar fetches to these beaches in the lake were used in an attempt to predict stable beach slopes. I Est1mates of bed shear under waves were made, allowing pred1ctions of likely sand movement for g1ven wave and current combinations I in the lake. I I I I I I I I I I I I
I 3 I I I 2. Model Investigation
I 2.1 The Model
The physical hydrau11c model was des1gned to study the tidal I current patterns 1n the proposed lake. The upstream boundary of the model was near Warwick Farm Racecourse and the downstream boundary near Riverwood Golf Course (see Figure 1). A small length of Prospect Creek was also I 1ncluded. Land forms above RL 103 were excluded from the model to I facilitate access. I 2.1.1 Model Scales The model scales were chosen on the basis of -
the requ1rement to simulate the flow phenomena (based on the I • s1m1larity cond1t10ns), I • the available area, • l1mitations on ava1lable funds. I The s1milarity condit10ns are der1ved from the hydrodynam1c equat10ns for free surface flows (Append1x A). The analysis shows that the model would completely simulate the prototype 1f the following four I cond1tions were met:
-os I (1) IFR (= uR(gR ~) ) 1 Fronde cond1tlon
( 11) ~ (= u h \I _1) = 1 Reynold's cond1tion I R R R ( 111) n (=xh- 1 ) = K -1 roughness condltlon R R R
I ( 1V) (= u X K • -1) = 1 eddy viscosity ~. R R R Reynold's condltion I Wh1le these conditions cannot be satisfied s1multaneously, there are c1rcumstances where deviation from the condit10n will not cause I large errors (1.e. scale effects will be m1nimal).
The follow1ng scales were chosen, based on a comprom1se between I minimiS1ng scale effects and sat1sfY1ng the restr1ction of available area and funds. (See Appendix B for de tu1s.)
(a) Length scale X 250 I R
I 4 I I I (b) Depth scale ~= 50 (distortlon = 5) I The followlng scales based on Froude slmllarlty are a guide but need not be applied exactly
(c) u ~os = I R 7.07 ( d) = 88,400 ~ uRXRhR I (e) tR XR~-l 35.4
(f) u h ~ R R 354 I 2.1.2 Model Capabilities I The model can be used to - • estimate flow patterns and velocities in the mainstream I areas, • identify reglons of low or zero velocity, • gauge the effects of changes in lake conflgurations on the I flrst two items.
I Because of the distortlon adopted, could not be theoretically used for -
estimatlng flow patterns and velocities in eddles or side I • bays, I • determinlng three-dlmensional velocity patterns.
However, model verlflcation (see section 2.1.6) suggests that I flow patterns and velocltles ln eddles can be more accurately modelled than anticlpated. I 2.1.3 Model Constructl0n The model was constructed wlthln concrete block walls rendered I for water tightness. Templates for rlver cross sections based on roughly 100 m intervals were obtained from the survey dated February to June 1978 by way I of computer plotted model sections (programme PROFL). The paper sections were taped to sheet aluminium and cut with a base at RL90*.
I * (1) The datum for levels 1S 100m below Standard Datum.
(ii) All dimensions are given in prototype scale unless otherwise I noted.
I 5 I I I The aluminium templates were pinned and levelled and the model area filled w1th sand to a level Just below the surface, the rema1nder I be1ng filled w1th a mortar capp1ng. The model surface was painted and 100 m grid lines placed across.
I 2.1.4 Model Operat10n
The model operation was organ1sed so that only one or two men I were needed. The model was filled to mean water level and then maintained by applY1ng a trickle supply w1th an overflow we1r to compensate for a I small amount of leakage. The water level was determ1ned by two v1brating t1P water level followers, which were 1nstalled at each end of the model. (Details of I these units and all other equipment used is g1ven 1n Appendix C.) The water level followers were also used to mon1tor water levels dur~ng testing.
Care had to be taken to avoid w1nd c1rculation by closing all I entrances to the model build1ng dur1ng model testing.
The flow was controlled by circulat1ng pumps for both the Georges R1ver and Prospect Creek. Flow in Cabramatta Creek was negligible I and not modelled. The flows were measured with 'gapmeters' and controlled with gate valves on the discharge l1nes.
I Flow directions were reversed by 1nterchang1ng the suction and d1scharge lines from the pumps. I F1gure 3 shows the model layout and the flow control arrangements.
I 2.1.5 Mon1toring of Flow Patterns and Veloc1ty D1stribut10n
The model was loaded pr10r to the commencement of test1ng with I white polystyrene drogues and paper confetti to trace the flow patterns 1n the model. The model surface was painted black to provide contrast for the I drogues and confetti. The movement of the drogues and confett1 was monitored uS1ng both t1me-exposure still photography and time-lapse mOV1e photography. The two cameras were mounted e1ther 9 m or 3 m above the model, depending on I whether the Ch1pp1ng Norton end or the Prospect Creek end was being mon1tored. The restr1ction of lens angle and roof height limited the field of view of the cameras to half the model area, necess1tat1ng repeat running I of each test for each end of the model. In all tests a v1sual inspection of water circulat10n to supplement the photographs was made, especially 1n those areas near the edges of the field of view of the still camera.
I A data board and electric clock were set up 1n the f1eld of view of the cameras to simp11fy identification of the photographs and I mOV1es.
I 6 I I
I The st1ll camera was operated by a solen01d from ground level uS1ng an extension lead. An auto winder advanced the film and re-armed the camera after every shot. A flash was synchronised at the start of every I IS-second exposure, so that the resultant trace conta1ned a dot at the start. I The mOV1e camera was also operated by a solenoid arranged to tr1gger every S seconds. Flood11ghts were used on the model to ensure that 1llumination for both cameras was adequate.
I Plan area measurements of the lake were used to allow for tidal storage in the lake. The correct10n factors thus derived were applied to the model result for use 1n subsequent 1nvest1gat10ns outlined 1n th1s I report. 2.1.6 Ver1f1cat10n
I In order to compare the c1rculat10n patterns and pred1cted velocities in the model w1th those of the prototype, Epsom Road was modelled and the bed of the northern pond was bU1lt up to the level I exist1ng at present.
Two float track1ng exercises in the f1eld were carr1ed out. I The first used two theodo11tes to follow drogues circulating near the W1ld11fe Island across the pond towards the northern bank. The second 1nvolved track1ng drogues by aerial photography cover1ng a larger area of the same pond. In connection w1th the aer1al photography, a computer I programme was developed to correct the results for camera t1lt (programme CNDRG). I Visual compar1son of c1rculat10n patterns revealed that qU1te a reasonable correlation exists between model and prototype. Moreover the rat10 between r1ver velocit1es and pond veloc1ties was of the same order I for model and prototype (see Figure 4). Th1S favourable compar1son suggests that the velocities with1n the shear generated edd1es can be modelled satisfactorily and the I c1rculat10n patterns set up 1n the lake will be more accurately modelled than ant1cipated. I S1nce no parameters such as roughness were changed 1n these experiments, 1t was considered that the model was ver1fied and d1d not require tuning.
I 2.1.7 Determ1nat10n of Testing Procedure I (a) 'Start-up' versus 'Long Term' Tests In order to determine a reasonable time over wh1ch to test the model, a compar1son was made between steady flow tests commenced from I quiescent cond1t10ns and day-long tests. It was found by studying the time-lapse record that an 'equi11br1um' flow pattern was estab11shed in a start-up test after approximately 20 minutes (11.8 hours prototype).
I A true equ1l1brium state was never reached in long term tests
I 7 I I
I of six hours (prototype) duration - the position of eddy centres shifted continually - but the velocities with1n the cells rema1ned constant. I (b) T1dal S1mulation versus 'Start-up' Tests The 'start-up' method of testing differs from rea11ty in that I the momentum of the flow from the preV10US tide is ignored. Tests were carr1ed out to compare the 'equ1librium' patterns from start-up tests to patterns generated by a t1dal simulation. The tidal I curve was modelled by a steady flow changing 1n d1rect1on only (F1gure 5).
After two full tidal cycles, 1t was found that a c1rculation pattern s1m1lar to that from start-up tests was generated for each flow I direct10n, approximately 4 hours after reversal of flow. Plates 1 and 2 compare the tidal and 'Start-up' patterns respect1vely for an ebb t1de, and I Plates 3 and 4 for a flood tide. Res1dual c1rculat10ns from the preV10US tide explained the rap1d development of the flow patterns compared to the1r slower I establishment in a start-up test. However, in areas of rapid circulation where the flood and ebb directions were reversed, the development of a typical start-up pattern 1n the tidal simulat10n was considerably delayed.
I For instance, the 'equ1librium' veloc1ty of the clockwise circulat10n in Georges Hall Bay on the flood t1de was higher than that of the anti-clockwise circulat10n on the ebb tide. When the tidal situation I was examined, circulat10n in the bay d1d not develop within the ebb half-cycle, and veloc1ties on the flood t1de were approx1mately half those I found in the start-up tests. It was eV1dent that, when using the start-up testing technique w1th a steady flow, the pred1ct1on of velocities 1n areas such as Georges Hall Bay would require some degree of judgment 1n assessing the effects of I residual t1dal flow. I (c) Sens1tivity to Water Level A check on the sensit1vity of the model to water level fluctuat10ns was carr1ed out to ensure that no ser10US errors were being introduced 1n the simulat10n by uS1ng mean water level for all tests, I whether flood or ebb.
The water level of the model was raised, while a steady flood I flow was app11ed. No change in the circulation pattern was observed and veloc1ty changes were min1mal between the high and low levels. I A second test w1th ebb flow and a decreas1ng level confirmed the above trends.
For large water level var1ations when submerged we1rs were I included in the model, d1fferent d1scharges over the weirs d1d cause minor changes to patterns set up on some occasions. The effects were localised and were deemed too small to warrant further investigation. Typical I results are shown in Plates 5 and 6 for a flood t1de.
I 8 I I
I (d) SensitiVlty to Flow
A test was carried out to determine whether altering the I magnitude of flow in the model resulted in any variation of clrculation patterns.
As flow was increased from a low value of flow to an I approximate peak tldal flow, no change ln pattern was observed, as demonstrated by Plates 7 and 8. I (e) Roughness Elements In order to verlfy the assumption that roughness requlrements can be relaxed for the model (see Appendix B), prototype roughness of the I bed was estlmated. Form roughness was then modelled as suggested by the Delft Hydraulics Laboratory (ref.2) using 50 mm cubes glued to the bed at a I spaclng of 400 mm. Comparison of tests of this area wlth the unroughened model showed little change in flow pattern and dlfferences ln velocity were I negllglble. Plates 9 and 10 show resultlng ebb flow patterns for the unroughened and roughened model respectlvely. I (f) Effect of Prospect Creek Comparison of tests carr led out wlth and wlthout Prospect Creek flow being lncluded in the model simulatlon showed concluslvely that this I does make a dlfference to the patterns set up ln Chipplng Norton Bay. Plates 11 and 12 show tYPlcal circulation patterns set up wlth and without Prospect Creek for an ebb tlde, and Plates 13 and 14 show representatlve I flood tlde patterns. It was evident that flow up or down Prospect Creek had to be included in the model to more accurately predict patterns in the region of I the Bay.
I 2.2 Model Results - Clrculation and Current Patterns From the considerations of section 2.1.7, it was resolved to run tests of the unroughened model for 1.5 hours duration, commenclng from I still conditlons (start-up test) using a steady flow and maintalnlng a mean water level. Thls allowed a full study to be made of the nature of the equllibrlum clrculation patterns produced. A number of conflguratlons were I tested. As stagnant areas were discovered, alterations were made ln an attempt to lmprove flow in these areas. One limitation was that no fill material should be added to the system unless absolutely necessary, so I existing landforms were utllised to adJust the lake configuratlon. Although a large number of configuratlons were trled. only those which showed signlflcant improvement were fully tested. Six of these I configurations are descrlbed in thlS report.
Although both conflgurations 3 and 6 provided adequate I circulation ln all parts of the lake. configuration 6 is recommended as
I 9 I I
I belng more economical.
The mean flow patterns illustrated in the report include no I correction factors for tldal prlsm reduction from the downstream end to the upstream end of the lake. I 2.2.1 Acceptance Criterla Each configuration was tested for adequate circulatlon. A section was said to have inadequate clrculatlon lf it was stagnant ln both I ebb and flood tldes. Further, if velocitles were so low that a particle had no chance of belng removed from one area to another in a tldal cycle, I the conflguration was rejected. 2.2.2 Conflguratl0n 1
The origlnal conflguration for the lake as proposed ln the Cox I and Corkll1 Report (ref.l) was used as a basis for the flrst configuratlon to be tested.
I Flgures 6 and 7 show representative 'equillbrium' flow patterns, approxlmated by a mean flow pattern, for/flood and ebb tldes. Those areas shown wlthout streaks were inadequately photographed, and do I not neccessarlly indlcate areas of 'no flow'. Slow to near stagnant areas were found to exist near the Wlldlife Island in the proposed marina near HOllywood Plcnic Area and ln I the proposed Flsh Nursery. All remainlng areas met the acceptance criteria. I 2.2.3 Conflguration 2 As shown in Figures 8 and 9, a 5 m wlde culvert joining the I boat harbour to the rlver channel improved clrculation in this area. Part of the bank dividlng the Fish Nursery from Chlpping Norton Bay was removed ln an attempt to flush out the near-stagnant areas. I Detalled testing of the Prospect Creek end of the model revealed that flow in the Fish Nursery was still lnsufficient. Circulation in Chipping Norton Bay had decreased considerably, since some flow in the bay was intercepted I by the gap in the bank leading to the rlver past the nursery. This end of the model remained unaltered untl1 Configuration 6 was tested.
To improve circulation in the northern sectl0n of the lake near I the Wlldlife Island, a submerged broad crested weir joining the southern bank of the lake to the island was included. It was anticipated that, by placing the welr ln the maln flow stream, more flow would pass lnto the I northern areas of the lake. The depth of water had to be greater than two metres, since the channel should be navigable at all times. I After testing thlS configuratlon, lt became clear that not enough flow was being diverted to the Wildlife Island (Flgures 8 and 9). I
I 10 I I I 2.2.4 Configuration 3 I As shown in Figures 10 and 11 remnants of Epsom Road were left 1n the lake as a ser1es of islands. The gaps between the islands compr1sed we1rs of 1dentical depth to the we1r in Conf1guration 2, and were of I sufficient width to allow access by boats to both lakes. The main effect of this pattern was to direct a large I proport10n of the flow around the W1ldlife Island. Areas of poor circulation in one flow direct10n c1rculated adequately when the flow was reversed. Water mov1ng over the weirs between the 1slands formed cells on the 'lee' side of the lake, so good exchange I was ensured.
There were no areas of stagnat10n for this conf1guration. I However revenue lost by leaving a large volume of sand under the islands was cons1dered exceSS1ve and cons1derable extra bank protection would be required. The loss of open lake area was Judged to be a further argument I against this configurat10n, and 1t was d1scarded as being economically unfeasible. I 2.2.5 Configuration 4 In order to create h1gher flows in the northern area of the lake, part of the peninsula div1d1ng Georges Hall Bay from the lake was I removed, the intention be1ng that the large eddy in the bay would 1n turn improve circulation around the W1ldlife Island. Epsom Road was totally removed.
I As can be seen in F1gures 12 and 13, this configurat10n was not satisfactory - the stretch of river beh1nd the Island 1n part1cular was almost stagnant. The large boat harbour at the upstream end of the lake I near Warwick Farm was also found to be slow moving.
A workable configuration combining configurations 3 and 4 was I found but not fully tested. 2.2.6 Configuration 5
I Th1S configuration 1nvolved leav1ng in position the western river bank at the downstream end of Chipp1ng Norton Lake, together w1th the I remnants of Epsom Road left as an 1sland of length approximately 150 m. A 5 m w1de culvert Joined the boat harbour to the river near Warwick Farm to 1mprove flush1ng 1n th1s area. Th1S proved ineffective I however, as flows through the culvert were not h1gh enough to produce satisfactory circulation.
Although the ebb tide (Figure 15) showed a poor circulation I pattern in Ch1pping Norton Lake, the flood tide pass1ng through the narrow constriction formed a jetting effect when it entered the lake. The Jet was deflected dramat1cally by the 1sland, and movement beh1nd the W1ldlife I Island was generated by eddies close to the northern bank. F1gure 14
I 11 I I
I demonstrates thiS phenomenon.
The river behind the Wildlife Island flowed in one direction I during a flood tide. but was stagnant on the ebb. The net result over a tidal cycle should be continuous flow in one direction. generated by the I flood tide and gradually decreasing during ebb flow. Flow around the two beaches on the Wildlife Island was adequate and should prevent build-up of debris in the area. However. since the main flow path was diverted away from the southern part of the lake. circulation I here was found to be unsatisfactory. I 2.2.7 Configuration 6 The opening to Chipping Norton Bay from the FiSh Nursery. tested in Configuration 2. was narrowed by extending the previously formed island. ThiS had the effect of forcing flow deeper into the small bays of I the Nursery. assuring flushing of thiS area on the ebb tide. Circulation in Chipping Norton Bay was improved since less flow passed through the gap I than previously. The culvert Joining the upstream boat harbour to the river was widened to 38 metres to allow more exchange between the harbour and the I lake/river system. The position of the island south of Georges Hall Bay was altered after it was realised that the position shown on the original plan I provided by Chipping Norton Project Section was incorrect.
To improve flow in the southern area of Chipping Norton Lake. a I culvert of width 18 metres was cut through the western river bank. The triangular island in Chipping Norton Lake was removed to I promote interaction between circulation cells in the south-western corner of the lake and the relatively quiescent areas near the beach at the southern end of the lake.
I Since details of a proposed beach on the northern bank of Chipping Norton Lake had become available. the groyne/beach arrangement was included in the model to determine itS effect. if any. on circulation I patterns. Figures 16 and 17 show results of tests on thiS configuration for flood and ebb tides respectively. Plates 15 and 16 demonstrate flow I patterns in the model for Configuration 6.
The incluSion of the northern bank beach in the model diverted I the main flow path on a flood tide away from the islands near the bank across to the area where the triangular island was previously located. Removal of the island promoted circulation at the beach near Charlton I Avenue. which was previously found to be in an area of unsatisfactory circulation.
Flow in the old river channel west of the northern bank beach I was reduced as a result of the diversion of flow in a flood tide. Ebb flow
I 12 I I I was found to be sat1sfactory in th1s area.
Flow through the culvert in the western bank formed a Jet I extending past the beach on a flood tide. further 1mproving circulation near the beach. I 2.3 Recommendations Configurat10n 6 (F1gure 18) proved to have adequate circulation 1n all areas and it is recommended that the lake be constructed to th1s I Conf1guration. The mean veloc1ties shown 1n F1gures 16 and 17 provided the basis for the subsequent invest1gat10ns. Where necessary. adjustments were I made for stage of the tide and for tidal prism. It should be noted that some conservative assumptions were made in an attempt to prov1de a 'worst case' (lowest veloc1ties) that could I reasonably occur. No allowance was made for the addit10nal circulation generated by wind. It 1S recognised that wind current would often dominate t1dal circulation and hence 1ncrease veloc1t1es in most areas. Th1S phenomenon was observed in the f1eld, when a marked change in wind I direction and strength was seen to generate currents of the order of 0.1 m/s. I Another conservat1ve assumption is the representat10n of the flow pattern by an average flow pattern. Observat10ns of the model flows revealed that a steady flow pattern never eX1sted. The position. size and strength of edd1es were constantly changing. to the point of disappearing I and reappearing in some cases. Even the ma1n flow paths were affected where they were bordered by side eddies. The effect of th1s was to constantly bring areas under the influence of different edd1es or currents. I thus 1ncreasing the chance of m1xing. I I I I I I I
I 13 I I I 3. Pollutants I 3.1 Introduct1on
Pollutants may be defined as substances added to the water as a I result of man's act1vit1es and having an adverse effect on the environment. Some of the pollutants which may affect Georges River include suspended sed1ment, faecal bacter1a, organic matter, waste water, excess algal and I macrophyte growth, litter, toxic chemicals, thermal pollutants and exotic organ1sms. I S1nce the mid 1960's, many invest1gat1ons have been undertaken on various pollution aspects of Georges R1ver. The State Pollution Control Commission (SPCC) 1S at present prepar1ng an extens1ve study entitled 'Environmental Control of Botany Bay and its Tr1butaries' (ref.3), which I collates much of the ear11er work and 1ncludes the results of investigation carried out or comm1ssioned by the SPCC. I Th1S report summar1ses some of the results presented in the SPCC study as 1t affects the Chipping Norton Lakes Scheme. Indications of the levels and trends of pollutant parameters are given by an exam1nation of data collected by the SPCC between 1971 and 1978. Where poss1ble, the I sources of pollutants are identif1ed, and f1nally the effect of the Lake I Scheme is examined using the results of the model study. 3.2 Parameters Used to Measure Pollution I The SPCC have been co1lect1ng data on the Georges River at monthly intervals since 1971 at stations approximately 3 km apart. From the many parameters monitored by SPCC, the six that have been chosen for this study, to gauge the level and trends of pollutants, are listed 1n I Table 1.
I 3.3 Levels and Trends
Plots of the parameters with time are given 1n F1gure 19. In I general, the values reflect the maX1mnm values found between Liverpool Weir and M1lperra Bridge. The one exception is DO where both maxima and minima are given, since there are relevant upper and lower bounds to sat1sfactory I levels. Since 1t is considered that rainfall would have a strong influence on the water quality, monthly rainfall figures - as well as I ra1nfall on the day prior to the data collection and the total ra1nfall for the five days preced1ng data collection - are included in the same figure. I I
I 14 I I
I TABLE 1: PARAMETERS USED TO MEASURE POLLUTION *
I Parameter· Pollutant Slgnificant Levels
Dissolved Overall indicator of water Less than 60% saturation I oxygen qual ity affects flsh. Between 65 and 110% saturation considered satisfactory.
I Faecal Indication of sewerage as Greater than 200 counts/ coliform a source of pollutant 100 ml unsatisfactory I bacterla for swimming. N113 Nutrlents Greater than 1000 ~g/l I unsatlsfactory level. BOD Organic pollutants Greater than 3 mg/l indica te s pre sence' of organic polluting I matter.
pH Non specific indicator, Expected to be between I e.g. industrial discharge, 6.0 and 9.0 but large algal blooms changes indicate pollutants.
I Turbldity Non speciflc indicator, Greater than 200 ftu e.g. agricultural runoff, considered abnormally storm runoff, extractive high. I industries, etc. I • A more complete descrlption of these parameters and their I significant levels is given in Appendix D. 3.3.1 Dissolved Oxygen (DO) I Slnce 1971 the levels of DO have been conslstently low enough to affect fish and invertebrates. It has been reported (ref.4) that there was a decllne ln DO between 1940 and 1972 that has now apparently levelled I out. Evidence of a seasonal fluctuation of DO is demonstrated by a least squares fit of a simple harmonic curve to the lower limltS of DO I measurements (Figure 20). The tendency is for higher levels to be recorded in winter and lower levels in summer, probably reflecting the lower bl0logical activity in winter. Dally fluctuations reported by the SPCC I (ref.s) reflect the effects of tldal flushing in the estuarine sectl0n. Upstream from Llverpool Weir, photosynthetic activity causes diurnal varlatlons during periods of algal blooms.
I Although the DO levels shown in Figure 20 are not correlated
I 15 I I
I with rainfall an examination on a finer scale 1n winter 1977 by the SPCC showed that heavy ra1n caused an immediate increase in DO between L1verpool Weir and Cabramatta Creek, but generally lower levels throughout the rest I of the r1ver. Recovery to former levels was slow, indicating the slow rate at wh1ch pollutants are flushed from th1s section. I 3.3.2 Faecal Coliform (E.coli) The levels of faecal coliform have been consistently high, I often above the level of 200/100 ml (2.3 on log 10 scale). There has been a trend of decreasing coliform levels (Figure 21). Th1S trend (stat1st1cally significant at the 95% level), if I continued, would result in consistently satisfactory levels being obtained in the early 1980's.
A plot of faecal coliform vs ra1nfall for the f1ve days prior I to data collect10n shows a s1gnif1cant trend of increasing coliform levels w1th increas1ng rainfall (Figure 22). In addition, the SPCC have found (ref. 6) that at anyone stat10n average faecal co11form levels are I generally h1gher at the lower recorded sa11nities, indicating a trend of 1ncreased co11form levels with high rainfall. I The dependency on seasonal effects is shown in Figure 23, where 1t 1S eV1dent that lower values are recorded 1n summer, probably because of the higher solar radiation levels.
I Other observat1ons made by the SPCC (ref.6) were
(i) Faecal coliform levels decreased downstream from I Liverpool Weir and were generally lower above the weir. I (ii) Cabramatta Creek usually recorded the highest levels. 3.3.3 Nutr1ents
I The level of ammon1a was only mon1tored consistently in 1975 and 1976 and during that time was found to be above 1000 ~g/L 20% of the time. This level is indicat1ve of the h1gh level of nutrients present, I resulting in exceSS1ve stimulation of plant growth, particularly algae, alligator weed and duckweed.
The SPCC studies have shown (ref.7) that nutrient levels in the I estuarine section are highest near Liverpool Weir, decreasing rapidly for 5 km downstream and then gradually over the remainder of the estuary. Upstream from the we1r, the h1ghest values are recorded near Glenfield I Water Pollution Control Plant. After heavy rain, a slug of nutr1ent rich water is flushed I through the estuary, taking about two weeks. 3.3.4 BOD
I The levels of BOD are consistently above 3 mg/l and hence
I 16 I I
I indicate the contlnual existence of organic pollutant matter. 3.3.5 pH
I The levels of pH are consistent with normal levels for rivers, i.e. 6 to 9 however lt is notable that the changes in pH have become less I slgnificant over recent years. 3.3.6 Turbidity I There has been a significant decrease in the variability as well as the level of turbldity between 1971/72 and recent years, indicating a trend of decreasing pollutlon. The correlation between turbldlty and rainfall shown ln Flgure 24, reflectlng the importance of runoff ln the I shale-derived sOlI catchments.
A 2l-day sampllng exercise by the SPCC (ref.S) revealed the I events that take place after heavy raln • Water turbldity lncreased throughout the tidal section I between Llverpool Weir and East Hl11s. • Recovery of the river to dry weather turbidlty levels was I slow (between one and four weeks) Recovery to low turbldity ln Georges River was faster at • Llverpool Weir and Kelso Creek than in the intermediate I river section. Above Liverpool Weir, freshwater flows rose then fell • quickly after rainfall. Much of the sediment settled out I in the ponded section above Llverpool Weir allowlng the overflow to flush more turbld water from the upper tidal I portion of the rlver.
I 3.4 Pollutant Sources 3.4.1 Water Pollution Control Plants
I Durlng dry weather, the WPCP. in the Georges River catchment provide a large proportl0n of the freshwater flow and are known to be the maln sources of nutrients and faecal coliform, and hence a cause of DO I depletion. I I • The Metropolitan Water Sewerage and Drainage Board refers to I sewerage treatment plants as water pollutlon control plants (WPCP). I 17 I I I Glenfield WPCP commenced discharging high quality effluent into the Georges River upstream of Liverpool Weir in 1972. It is licensed to discharge 30:20 effluent. at a rate of 15,000 cubic metres per day. Prior I to that time it is thought that discharge of waste from septic tanks occurred regularly.
I Liverpool WPCP is licensed for 30:20 effluent at 15,000 cubic metres per day and has been discharging into Georges River at Warwick Farm I since 1970. Other treatment works in the area are Fairfield WPCP that discharges into Prospect Creek via Orphan School Creek, the Commonwealth Treatment Works at Moorebank discharging at Casula and, prior to 1972, I Campbelltown WPCP.
As a response to the expanding population, the loads from the I treatment works have increased from the early 1970's to the present. Contrary to the expected decrease in water quality there are some indications, notably faecal coliform reduction, that the water quality is I improving. This has possibly resulted from improved treatment technology and inclusion of some areas in the sewerage reticulation system that discharges at Malabar Ocean Outfall.
I 3.4.2 Urban and Rural Runoff -- Turbidity
During times of heavy rainfall the waters became noticeably I more polluted. Urban runoff, overflows in the sewerage reticulation and excess loads on the treatment works. are known to contribute significantly to the levels of nutrients, faecal coliform, turbidity and toxic chemicals.
I The major source of suspended sediments is the erosion associated with agriculture and developing urbanisation. Prospect and Cabramatta Creeks drain catchments with shale-derived soils, leading to I very fine sediments.
The bed of the Georges River can be discounted as a source of I turbidity Since it is primarily sand. The contribution of sand mining operations has been shown by Warner and Pickup (ref.9) to be relatively minor by comparing the recovery I time of turbidity to normal levels after mining (24 hours) with the recovery after rainfall (several weeks). I I • 30:20 effluent - less than 30 mgll suspended SOlids I - less than 20 mgll BOD I I 18 I I I 3.4.3 Waste Dlsposal Tips
Leachate from waste disposal tips supplies minor quantities of I nutrlents. toxic chemlcals and faecal coliform. I 3.4.4 Other Sources At present. no industrial waste waters contalning signiflcant levels of tOX1C substances are licensed for discharge in the Georges Rlver basin. Illegal discharge is not thought to be a problem because of the I penalties and the availabillty of legal disposal sites. However. sediments containing elevated levels due to lndustrlal discharges in the past may act I as sources. Illegal dumping of rubbish from the shores provldes much of the vislble pollutlon such as car bodles. plastlc contalners. as well as I putrescible material such as food waste.
3.5 Effects of Lake Scheme on the Movement and Dlsperslon of I Pollutants
The construction of the Lake Scheme will have several effects I on pollutant dynamics. some beneflclal and some detrlmental:
(i) Downstream from the lake the tldal discharge wlll lncrease as a result of the greater waterway area avallable. Higher I tldal velocltles and greater tidal excursions should result ln lmproved mlxlng and dlspersion of pollutants.
I (ii) The higher veloclties downstream from the lake would result in increased friction and hence sllghtly reduced tidal levels. Hence the sltuatlon upstream from the lake I would be the opposite of that downstream - decreased tldal prism. lower veloclties. shorter tidal excursions and decreased pollutant disperslon. The effect is not I expected to be major. (lil) The flow pattern wlthln the proposed Lake Scheme wlll be such that no stagnant areas exist. ThlS will be an I improvement on the present sltuatlon where there are several ponds wlth mlnimal connection to the malnstream.
(iv) An examination of tidal excurSlons withln the Lake Scheme I was made uSlng the results of the model study
• typical flow paths for mainstream flood and ebb currents I were deflned from the averaged model results (Flgures 25 and 26). Dye was used as a visual check on flow paths in the model. Typlcal results are shown ln Plates 19 and I 20. • velocity correction factors were deduced for stage of I tlde from field tlde measurements.
I 19 I I
I correction factors were also deduced for tidal prisms using • plan area measurements of the lake (as mentioned in 2.1.5).
I the movement of a water particle during a tidal cycle was • simulated using a model with half-hour t1me steps. In regions of rapid change. the time steps were subd1vided. The results I are shown in Figures 25 and 26. • the results for several tidal cycles were concatenated to yield an impress10n of t1dal res1duals I (Figure 27). I The s1mulation provided several results: (a) Along the ma1n flow paths a pollutant will always move from one section to another within a half-tidal cycle. e.g I from Chipping Norton Lake to Georges Hall Bay. (b) In most of the s1de bays. the circulation 1S rapid enough to provide at least one revolution per half-tidal cycle. I (either flood or ebb).
(c) The t1dal residuals indicate that there 1S a tendency for I downstream movement in the mainstream (and hence an upstream movement in the side bays) thus assuring overall circulat1on.
I The 1mplication for pollutants is that there is enough movement with1n the lake to prov1de adequate m1xing. espec1ally when it is real1sed I that two factors have not been 1ncluded - • the unsteady nature of the mean flow patterns I • wind circulation. I 3.6 Conclus10n The study of some of the pollutant ind1cators has shown that the water qual1ty in the Ch1pping Norton area is far from 1deal for I recreat10nal use. espec1ally if swimming 1S to be expected. The levels of DO are consistently low. nutrients are high. faecal col1form are often present 1n high numbers.
I The construction of the lake scheme w111 have relatively minor effects on the behav10ur of the pollutants:
I • greater mixing and dispersion downstream I • slightly less mixing and dispersion upstream • acceptable c1rculat1on and mixing will exist w1thin the Lake I Scheme.
I 20 I I I Stratification I 4. 4.1 The Problem of Stratif1cation I With the planned w1den1ng and deepen1ng of the ponds and the resultant decrease in t1dal velocit1es, there eX1sts a poss1b1l1ty of dens1ty stratification. The Metropolitan Water Sewerage and Dra1nage Board (ref.lO) have expressed concern that such stratification may result in I deoxygenation at depth and hence the development of noxious conditions.
I 4.2 Cond1t10ns for Strat1f1cation For stratification to eX1st, there must be sources of waters of differ1ng densit1es. In this case, the d1fference between salt water and I fresh water is enough to cause a dens1ty differential of 3%. Another possible cause for density d1fference is temperature, wh1ch 1S less l1kely to be s1gnif1cant since a temperature difference of 20 0 C g1ves a density I difference of only 0.4%.
Despite the existence of fluids of different density, I stratification will not occur or be maintained if the m1xing processes dominate the gravitat10nal effects. In an estuary, th1s can be expressed as 'the ratio between t1dal energy d1ssipation and the rate of gain of I potent1al energy determines the degree of strat1f1cat10n.' Harleman and Abraham (ref.11) have expressed th1s ratio as an I 'Estuary Number': I E ". P where T hdal prism Vo = peak tidal velocity at the entrance I g = gravitational acceleration h depth Of = fresh water flow I T = t1dal period Harleman and Ippen (ref.12) state that the tranS1t1on from I strongly strat1fied to well mixed estuaries is 1n the range 0.03 I 21 I I I 4.3 App11cation to Present Situat10n I 4.3.1 Fresh Water Inflow Dur1ng dry weather, fresh water 1S ma1nly provided by the sewerage treatment works. The SPCC (ref.5) have estimated a flow of 26,000 I cub1c metres/day from the works at Holdsworthy, Liverpool and Glenfield, compared with est1mates of dry weather base flow ranging from 5000 to I 10,000 m'/day. The adopted fresh water flow 1S Qf = 30,000 m'/day = 0.35 m3 /s I 4.3.2 T1dal Pr1sm From a data collect10n exerC1se conducted by the Pub11c Works Department on Apr1l 27th, 1978(13), the volume of water passing East H1lls I in both d1rect10ns was 2 x 10' m'. Since there 1S little phase lag between th1s point and the end of the estuary, thls value is taken as the I t1dal pr1sm : I From the same report, 3 m I 0.65 m/s The sall~lty at East Hliis can be as h1gh as 25%0 so I the rat10 p/Po = 1.01 E' = I This value, be1ng well above the l1m1t of 0.3, ind1cates a well m1xed I estuary. 4.3.3 Observations of Density Prof1les Temperature/sa11nity profiles have been recorded on many I occaS10ns by the Hydrau11cs Laboratory as well as other observers. In almost every case, the dens1ty has proved to be unlform w1th depth. I The h1ghest dens1ty difference reported by the Hydrau11cs Laboratory was 0.3%0 at Prospect Creek on 9/3/78. I The h1ghest dens1ty d1fference reported by the SPCC (ref.14) was 0.6%.near L1verpool Weir. There are areas 1n the present system w1th large ponds connected to the r1ver but w1th very poor circulatlon. These I areas show very l1ttle tendency for strat1f1cat10n. I I 22 I I I 4.4 Effect of Lake Scheme I The proposed lake scheme will • decrease velocities within the lake, and I • have a greater depth, both of which Increase the possibility of stratification. I On the other hand, the lake scheme will have a larger tidal prism which will tend to decrease the possibility of stratification. A low (conservative) estimate of E' In the lake at Prospect I Creek using a velocity value obtained from the model study IS - E' = 0.03, I which Indicates a possibility for stratification. I 4.5 Recommendations It is not Intended to carry out further Investigations at this stage. Even If more detailed computations resulted In an accurate I prediction of stratification, no changes in the proposed configuration would be recommended. I This configuration exhibits reasonable circulation in all areas under normal tidal flow and there IS little scope for further improvements by changing the boundaries. I It IS recommended that the salinity/temperature profiles be regularly monitored and, If a stratification problem does eventuate, then I thought be given to artificial means of overturning the layers. I I I I I I I 23 I I I 5. SedImentatIon I 5.1 Suspended Sed1ment I 5.1.1 Prev10us Investigation The Water Research Laboratory had previously estimated that the Lake would trap 29,000 tonnes of suspended sediment per year (ref.15). I When compared with the quantity of sand to be dredged from the lake (10 x 106 tonnes), it is seen that' ••• siltat10n over the next 100 years I presents no problems'. 5.1.2 Suspended Sediment Data I The results for the prev10us 1nvestigation were based on a suspended sed1ment of 140 mg/l derived from six samples collected on two occasions. F1ve of the samples were collected dur1ng a 1 1n 5-year flood I (see Table 2). I TABLE 2· SUSPENDED SEDIMENT CONCENTRATIONS (Taken from Ref. 15) I Sample Date Concentra Hon Flow Loca Hon No. mg/l Cond1t1ons I 1 14/5/67 106 Nil Georges R1ver upstream of Cabramatta Creek I 2 7/8/67 260 1 in 5-year Georges R1ver Cutler flood Road I 3 7/8/67 260 1 1n 5-year Georges R1ver at flood Ch1pping Norton 4 7/8/67 360 1 in 5-year Cabramatta Creek I flood 5 7/8/67 460 9 ft.9 in Prospect Creek I on gauge at Road Bridge 6 7/8/67 140 Georges R1ver at I Liverpool We1r I However, since then, more data has been collected by the State I Pollution Control Commiss1on, as well as by the Department of Public Works I 24 I I I Hydraulics Laboratory over 34 separate days and cover1ng a wider range of flow cond1tions. I Table 3 shows the results obtained as well as the corresponding flow condit1ons. I Qualitatively it can be seen that low concentrations (less than 50 mg/l) correspond to low periods of ra1nfall and high concentrations correspond to high periods of rainfall. Only on two occasions (14/5/67 and 5/9/72) was there a coincidence of h1gh concentrat1on and low rainfall. It I is poss1ble that mining act1v1ty caused the high concentrat1ons on these dates. This is suggested by the loca11sat1on of h1gh suspended sed1ment concentrations at Cabramatta Creek on 5/9/72. Unfortunately the records of I the min1ng are not deta1led enough to conf1rm th1s hypothes1s. I 5.1.3 Siltation Estimate Using a more reasonable estimate of the dom1nant suspended sed1ment concentration of 30 mg/l. the resulting quantity of s1lt entering I the lake is 2 x 104 tonnes/year. assum1ng that the lake has 100% capture. W1th a lake surface area of 1.4 x 106 m3 • an upper bound to I the decrease 1n water depth 1S 0.05 m/year. 5.1.4 Conclusion It is conf1rmed that there would be no problems associated with I reduct10n of lake depth as a result of suspended sediment. unless there is I a dramatic change 1n the quantities being transported by the Georges R1ver. I I I I I I I I 25 I I I TABLE 3: SUSPENDED SEDIMENT DATA I Date Concentration Flow Location Source mg/l Conditions of Data I 14/ 5/67 106 Little rain for Upstream of Ref.15 over 1 month Cabramatta Ck. I 7/ 8/67 140 to 460 1 In 5-year Cutler Road Ref.15 flood I 12/ 8/71 5 Little rain East Hills to Ref.16 Mllperra Bridge I 7/ 9/71 7 14/10/71 1 to 9 I 30/11/71 2 East Hills to Georges Hall I 94 Cabramatta Creek 4 • • Liverpool Weir I 27/ 1/72 35 to 140 50 mm rain East Hills to previous day Liverpool Weir I 29/ 2/72 7 to 57 No rain for prevIous 1.5 I weeks 13/ 4/72 4 to 112 Heavy rain I prevIous week 30/ 5/72 2 to 20 Little run for I over one month 13/ 7/72 7 to 57 No rain for East Hills to previous 4 weeks Liverpool Weir I 5/ 9/72 17 to 27 No rain for 1 wk. East Hills to - llttle rain Georges Hall I for 3 weeks 243 Cabramatta Ck. I 8 to 27 Liverpool Weir 10/10/72 2 to 17 Little rain for East Hills to I prevIous 2 mths. Liverpool Weir I 26 I I I 23/ 4/75 13 to 39 No run for preVl0US month I 7/ 8/75 7 to 18 No rain for 1mth. I 2/ 9/75 2 to 8 No rain 2 mths. 1/10/75 8 to 32 Llttle rain for East Hills to 3 months Liverpool Weir I 20/11/75 3 to 22 Llttle raln for 4 months I 25/11/75 8 to12 Some rain during week I 6/ 1/76 9 No rain 2 mths. 11/2/76 8 to 12 Llttle raln for I last 2 weeks 5/4/76 20 No raln 2 weeks I 28/ 6/76 20 to 32 Some rain Mllperra Brldge preVlOUS week to Llverpool Weir I 11/ 8/76 8 to 29 No rain 1 week 6/ 9/76 12 Little raln for I past 2 months 11/10/76 18 to 34 Little raln I 15/11/76 11 to 34 Llttle raln I 21/12/76 5 to 41 Very little rain 4/ 5/77 0 to 10 No rain 2 mths 0 East Hllls to Ref.17 Llverpool Wll'ir I 3/ 4/78 375 to 650 Tall end of Ml1perra Bridge minor flood I 27/ 4/78 9 to 45 Not much raln East Hllls to Ref.13 since beglnnlng Cabramatta Creek of month I 17/11/78 31 to 59 Moderate rain Georges Hall P.W.D. for 2 weeks Straight Hydraullcs I Laboratory 11/12/78 5 to 13 No rain 1 mth. Wildlife Island 18/ 4/79 0 No rain for I almost 1 month I 27 I I I 5.2 Sand Transport I 5.2.1 Previous Investigation The Water Research Laboratory had carried out investigation into sand bed load for floods and freshes for a reach of the Georges River located upstream of Liverpool Weir (ref.lS). A flow duration curve was I synthesised from 18 years of records for the Nepean River and Nepean Dam. thiS was combined with a bed load rating curve to obtain an average annual bed load of 26,400 tonnes of sand. Further combination with flood I hydrographs gave figures for total sand transported as bed load by floods. Amounts of sand thus derived were 2,640 tonnes for a 1 in 2S-year flood and I 12,700 tonnes for a 1 in 100-year flood. The average annual advance of a sand delta, which will be formed at the upstream end of the lake, was calculated to be 6 m per year. The conclusion was made that 'maintenance dredging will be infrequent and I therefore presents no problems. thiS is particularly the case since the sand is a marketable product with an economic value'. I 5.2.2 Bed Load Estimate The bed load calculations carried out by the Water Research Laboratory (section 5.2.1) were checked for a section of the Georges River I upstream of Warwick Farm, where the flood plain is relatively narrow. Two bed load formulae were used for the purposes of comparison the Meyer-Peter and Muller formula (ref.18) and the Einstein-Brown formula I (ref.19). The latter method predicted slightly higher bed transport rates for high order floods, but generally the comparison was reasonable. I The results of the study indicate that use of the sediment rating curve recommended by the Water Resources Laboratory (ref.lS) is reasonable for the prediction of bed load in Georges River for freshes and I floods. I 5.2.3 Total Load Estimate The total sediment load is the sum of the bed load and the suspended load. The suspended load is supported by turbulent currents and I could be significant for flood flows on the Georges River. The Colby approach (ref.19) was used to calculate expected total sand loads for a range of flows between 1 in 3-year and 1 in 100-year I floods. Transport rates for the total load varied between ten times the rate of predicted bed load for low order floods, down to five times the bed load for 1 in SO and 1 in 100-year floods. These results suggest that sand I in suspenSion forms a significant part of the total transport during floods. The Water Research Laboratory (ref.lS) only considered bed load I transport of sand and they underestimated the total sand dropped into the lake by floods and freshes. I Correction of the values quoted by the Water Research I 28 I I I Laboratory suggests that the total sand transported can be as hIgh as 63,000 tonnes for a 1 In 100-year flood and 17,000 tonnes for a 1 in 25-year flood, assuming these amounts of sand are available upstream. The average annual advance of the delta at the upstream end of the lake will be I of the order of 30 m. I 5.2.4 ConclusIon The above analysis of sand transport in the Georges RIver suggests that Reference 15 has under estimated the total sedIment load of I the river under flood condItIons. Despite this fact, the conclusions of this study are simIlar to those of the Water Research Laboratory expected quantitIes of sand should present no shoaling problems In the lake I and maintenance dredging at the headwaters of the lake will be infrequent. I I I I I I I I I I I I I 29 I I I 6. Movement of EXisting Bed Fines I The method of sand extraction employed at Ch1pp1ng Norton results in a layer of f1ne sediment be1ng deposited in enclosed ponds. It is feared that when the ponds are opened to be incorporated in the Lake I Scheme, the fines will be brought into suspension, increasing the level of turb1dity 1n the river. The 11kel1hood of th1s occurring was examined by compar1ng the I shear required to 1nitiate bed movement to values of shear derived from the model experiments. I 6.1 Characteristics of the F1nes Bed samples were obta1ned from the ponds on either side of I Epsom Road and analysed by hydrometer for particle size grading. A typical grading curve (F1gure 28) shows the bed mater1al to be clayey silt with I med1an gra1n diameter of 0.003 mm and almost no sand fract10n. The layer thickness was 1nvest1gated by Survey Branch of the I Department of Public Works using a dual frequency echo sounder. The silt layer was found to vary between 0.0 and 0.5 m th1ck, w1th mean th1ckness 0.17 m. There was no sign1ficant difference between I mean layer th1ckness on each side of Epsom Road. I 6.2 Cr1tical Shear Samples of the lake bed were used in laboratory tests to determ1ne the shear required to in1tiate motion. The sample was placed 1n a trench 1n the bed of a flume so that the top of the sediment was level I w1th the flume bed (Figure 29). Two methods of placement were used. In the first, the sed1ment I was mixed w1th water and allowed to settle 1n place. In the second, the sample was placed as it came from the field, and the flume subsequently I filled with water. A jet of water with constant flow was d1rected towards the sample w1th the nozzle/sample d1stance being altered until sediment I movement was 1nit1ated. From the measured distance to the sample and the known flow rate, the shear was estimated uS1ng the relations developed by RaJaratnam I and Pani (ref.20). A check on the applicability of the theory was made by comparing measured velocity with the pred1cted velocities. In three out of four experiments the d1fference was less than 10%. I The values of crit1cal shear obtained ranged from 0.013 Pa to 0.093 Pa w1th no sign1ficant difference resulting from the placement I method. The conservat1vely assumed crit1cal shear 18 - I 30 I I I 0.02 Pa I 6.3 Available Bed Shear in Tidal Flow As expression for bed shear in open channels is given by(ref I 18) I where p water density V Mean current velocity I h water depth r = equlvalent sand grain size for bed roughness It is not known what the roughness of the bed would be after I dredglng, although lt could probably be assumed that the roughness parameter r would be of the order of 0.01 to 0.1 m. In thlS case the mean velocity requlred to generate a bed shear of 0.02 Pa ranges from 0.08 to I 0.1 m/s. Figures 30 and 31 show the areas of the lake scheme where it is predicted that the fines wasted from the sand mining operatlon would be I eroded for an average tldal flow and for the tide peak. It is likely that durlng moderate floods bed fines ln all areas I would be subject to erosion and hence would affect turbidity. I 6.4 Conclusions It is antlcipated that the sediments deposited in the dredged ponds will be eroded slowly in a normal tidal cycle and more rapldly during I floods. Although the contributlon of extraction deposits to turbldity I may eventually decrease due to the depletlon of these deposits, the problem of turbldity will remain because of the fines transported from the upper I catchment in tldal conditl0ns. I I I I I 31 I I I I 7 • Stability of Be~ch('s 7.1 Introduction I To minlmlse erosion of the banks ~f the lake from wave action, two forms of bank protection are to be adopted: rock protection and the constructlon of flat beach slopes. The latter has the advantage of being a recreational facillty, provlding landing areas for boats and canoes, and I allowing easier access to the lake. In order to dissipate wave ene~gy Ou the beach without ~emoving I excessive amounts of beach materlal, beach slopes and their extent offshore need to be determined. Recommendations for beach slope, offshore slope and toe depths I are made in the following sections. I A full analysis was carr led out for two beaches - the beach near Hollywood Drlve, being subject to small effective fetches an~ hence low wave climates, and the proposed beach to be constructed between two rock groynes on the northern bank of Chlpplng Norton Lake, near Georges I Rlver Road (see Flgure 32). This beach would be subject to a moderate wave cllmate, being open to longer fetches from the south-south-west. Calculations are provlded ln Appendix E. I All other beaches will be subject to condltions somewhere between the two beaches analysed. Appendlx E lists the expected wave I cllmates for beaches in the lake scheme. I 7.2 Stabillty of the Foreshore Slope In general, the variables affecting beach slope stablilty are the grain size of the beach materlal and the nearshore wave and current I cllma te. In order to attempt to determine a relatlonship between the variables, a brief analysis of data collected on beaches of similar fetches I to those in the proposed lake was carried out. A plot of foreshore slope against medlan grain size showed no slgnlflcant trend of steeper slopes corresponding to increasing grain Slze. I Slnce the fetches were different ln both dlrectlon and length for the beaches, some adjustment of the data to account for condltions prior to the fleld trlps should have been made. Lack of detalls of wave cl1Mate for the I period involved made thlS adjustment lmposslble. The probable sorting of beach sediment along a prof lIe also lntroduced errors, since a single sand I sample only was taken at each beach. It was decided to revert to existing publlcatlons to predict a 'stable' slope for beaches ln the proposed lake scheme. I Curves provlded by two references (20 and 21) showed good I 32 I I I correlation between median sand diameter and beach slope. Figure 33, reproduced from ref.22, ased only those samples colle~ted in a m~d-tidal reference sectl0n of the beach face. This achieved a reduction in scatter I due to sorting along a profile. The depths of sampllng was not stated. Curves glven in reference 21 agree reasonably with Figure 33 for protected I beaches, but deviate considerably for the more exposed cases. For a median sand diameter of 0.3 mm, Figure 33 suggests an average slope of between 1:10 and 1:12 for a protected beach. The Water Research Laboratory (ref.lS) recommends beach slopes between 1:10 and 1:IS I for all beaches ln the Lake Scheme, based on similarly protected beaches in Sydney Harbour. I In the absence of more detailed information lt was decided to adopt a 1:10 slope for beaches in the lake, wlth the exception of those beaches on the Wlldlife Island, the beach near Charlton Avenue, and on the I Northern Bank. These beaches at the north end of the lake, being subJect to long fetches from the south-west, should in theory have a flatter 'stable' slope than those more sheltered beaches with limited effective fetch. The recommended slope for these beaches is 1:13, which lies between I curves for protected and moderately protected beaches shown in Figure 33. The adopted slope for the proposed beach to be constructed on I the northern bank, however, will be 1:10. A potential cost saving wl11 result if sand losses prove minimal. If beach nourlshment is requlred, costs involved will be comparable with building the beach slope to 1:13 I inltlally. I 7.3 Stabillty of the Offshore Slope The offshore slope in qUlescent condltions could theoretically be left to settle at the angle of repose of the material, ln thlS case I approximately 32°. However as section 7.4 will explain fully, under wave actlon and/or currents in the lake, resulting bed shears may be sufficient to initiate motion of the sand particles on or near the offshore slope, which could result in a permanent loss of sand to depths of 8 m at I the lake bottom. For steeper offshore slopes, less shear is required to move the I bed material on that slope than that required on a near-horizontal bed. The factors glven below (ref.18) apply to a sand of angle of repose of 32°. They represent the critical tractive force on the slope I as a fraction of the value for a level bottom, for non cohesive material I only. I I I 33 I I I Bed Slope Factor I Horlzontal 1.00 1:4 (14.00 ) 0.88 1:3 (18.4°) 0.76 1:2 (26.6°) O.SI I 0 1: 1. 73 (30.0 ) 0.30 FroD bed shear stress calculations (see 7.4), lt was resolved I to select an offshore slope of 1:3 as being suitable for beaches in the proposed lake scheme. The decrease ln stress at the bed required to move bed material for a 1:3 slope was not exceSSive, whereas for steeper slopes I much higher sand losses for design conditions would be lncurred. At a depth varylng with wave and current conditions at each beach, the offshore slope can be increased to 300 with no loss of I stabl1lty. The depth of thlS transition point follows from calculations of bed shear stress from sectlon 7.4. I 7.4 Depth of Beach Toe The toe of the beach is deflned as the point where beach slope I and offshore slope intersect. thiS point should ldeally be located at sufficient depth to avold bed shear stresses severe enough to initlate I movement. For beaches ln the lake system, three posslble deslgn I conditions had to be examlned - (i) wave actl0n only, ( 11) tldal current only, I ( iii) combination of waves and currents. I 7.4.1 Bed Shear Under Waves An outline of the method used to predict the likelihood of partlcle movement under waves is glven ln Appendix E, whlch also lists the I design conditlons adopted for the investigatl0n. Although swimming will be prohlblted in the lake, it will undoubtedly occur. For safety reasons a minimum toe depth of 2.0 m below I Indian Spring Low Water was chosen, givlng an upper limit of RL.97.3 m. ThlS will minimise the possibility of a poor swimmer wading out past the gentle 1:10 beach slope and getting lnto difficultles in suddenly deep I water. ThlS depth is Sllghtly more conservative than the recommended depth of 1.83 m (ref.lS), based on observed beach sections in Sydney Harbour subJect to slmilar wave conditions. To ensure that a conservatlve depth was recommended, movement on the 1:3 slope was predlcted rather than I movement on a flat bed. At Mean Low Water Neaps (MLWN), adopted as a design water level I for prediction of sedlment motlon, bed shear due to waves at the beach near I 34 I I Hollywood Drive was estimated at 0.113 Pa for the minimum toe level at RL 97.3 m. Insertion of th1s value of shear 1nto the Shields Diagram (F1gure I 34) provided in Appendix E pred1cts no motion on a 1:3 bed slope. S1milar calculat10ns for the proposed beach on the northern bank 1nd1cate that bed shear stress of 0.39 Pa will eX1st for MLWN water level, and movement on a horizontal bed seems l1kely. Further calculations I for the beach suggest that at a depth of 3.4 m over the toe, bed shears marginally suff1cient to move sand on a 1:3 slope eX1st, but bed mater1al I on the flatter beach slope w1ll remain stable. 7.4.2 Bed Shear due to T1dal Currents From model testing results of the final lake conf1gurat10n, I mean tidal velocities l1kely to occur near the toe of the beaches 1n the lake were determined. I US1ng a logarithm1c veloc1ty d1stribut1on, bed shears were predicted from wh1ch the presence of mot1on uS1ng the Sh1elds D1agram, I der1ved for the offshore slope of 1:3, was determined (F1gure 34). At the proposed beach near Hollywood Drive, mean tidal veloc1t1es w1ll be 0.14 mls and 0.07 mls for flood and ebb tides respectively, as determined from model testing results. Bed shear stresses I due to the mean tidal current alone are not capable of 1nitiating sed1ment motion on either tide at Mean Low Water Neaps. A s1m1lar conclusion was reached for the beach on the northern bank and, indeed, for all proposed I beaches in the lake scheme. At peak tidal flows, some longshore movement can be expected, but the short duration of this event makes losses I neg11g1ble. 7.4.3 Bed Shear Due to Wave and Current Comb1nation The effect of a steady current superimposed on the orb1tal I velocity under waves is an 1ncrease 1n bed shear stress, poss1bly causing sed1ment transport, even though the shear from the current alone may not I initiate motion. Using the method for combined current and wave act10n out11ned in Appendix E, a ratio of the shear for the combined case to the shear for I waves only is derived. The increase in bed shear due to this comb1nation was calculated for the beach near Hollywood Drive. These calculations (see I Appendix E) 1nd1cate that stab1lity will be achieved for a toe depth of 2.6 metres below MLWN, 1.e. RL 97.2 m. At this depth, the comb1nat1on of wave act10n (caus1ng a shear at the bed of 0.094 Pa) and a mean tidal veloc1ty I of 0.14 mls at the surface (corresponding to the veloc1ty in the eddy near the beach for a flood t1de), cause a total shear stress at the bed of magnitude 1.6 x 0.094 or 0.15 Pa. Th1S value represents a cr1t1cal shear I value for a 1:3 slope as pred1cted by the Shields D1agram (F1gure 34). It is therefore recommended that the beach toe be located at RL 97.2 m for the beach near Hollywood Dr1ve. At th1s depth, sand movement I could occur for peak t1dal flows but, as concluded 1n section 7.4.2, losses I 35 I I I will be negligible. The beach on the northern bank 1S subject to a mean tidal veloc1ty of 0.1 mls for a flood tide. in a d1rection 0ppos1ng the direction I of wave mot1on. Tidal c1rculation near the beach for an ebb t1de is virtually zero. I The combination of flood tide veloc1ty and des1gn wave condit1ons 1ncreases the value of bed shear due to wave action of 0.074 Pa by a factor of 1.86 for a water depth of 4.0 m. The result1ng bed shear of I 0.14 Pa is close to cr1tical for a 1:3 slope. and bed material near the toe should be marginally stable. A toe at RL 95.8 m 1S recommended for the proposed beach on the I northern bank of Chipp1ng Norton Lake. Construct1on of the toe at a shallower depth than that I recommended may be warranted for this beach. As discussed briefly in section 7.2. a saving 1n construction costs could be achieved 1f a less conservative configurat10n 1S adopted and sand losses prove to be minimal. The upper 11mit of the toe at RL 97.3 m for safety will apply when a toe I depth 1S selected. At th1S m1nimum depth at MLWN. theory pred1cts erosion of the offshore slope at the toe for waves ar1sing from a wind greater than I 35 km/h from the south-south-west comb1ned w1th the mean t1dal flow. Circulation near beaches 1n the lake scheme will be wind dominated rather than tide dominated. Th1S fact lim1ts the confidence w1th I Wh1Ch actual values of bed shear stress can be predicted for the case of current and wave comb1nation. since t1dal current velocit1es may no longer apply. I The velocity of currents 1n the lake generated by wind were not determined. The unpredictable nature of return currents which w111 exist in the lake. particularly near a boundary such as a beach. make numer1cal I modell1ng of such a situat10n extremely difficult. A vast amount of f1eld data would be requ1red for vary1ng w1nd conditions before any attempt at modelling could be made. This was cons1dered to be outs1de the scope of I the investigation. Levels for the change 1n offshore slope from 1:3 to 1:1.73 were calculated by the same method. The critical value of shear. determined by I the steeper slope. of 0.06 Pa was adopted. I 7.5 Level of Back of Beach For design wave condit10ns at the proposed beach on the northern bank. analysis was carried out to determine a lower lim1t for the I back of the beach to avoid overtopping. Values of w1nd setup. wave setup and wave runup were calculated. A sufficiently extreme event for des1gn was Mean H1gh Water Springs (RL 100.82 m) with the design wave climate I glven in Append1x E. For these tidal conditions. total set-up can ra1se the water I level to RL 100.94m. with runup adding a further 0.17 m height to RL 101.11 I 36 I I I metres. The level at the back of the beach from lnltlal designs I supplied by the Chlpping Norton Lake Scheme show RL 101.66 as being typical. Under extreme conditlons, a beach width of approxlmately 5.5 m I will remaln clear of the influence of wave runup. All other beaches, being subject to smaller wave cllmates and smaller fetches, will be satisfactory if designed to the same upper beach level as the northern bank beach under examination. The order of accuracy I of the analysis does not warrant any reduction ln level for more sheltered I beaches. 7.6 Recommendatlons I Recommended beach profiles are provlded for all beaches in the Lake Scheme in Flgures 3SA and B. These profiles should be satisfactory to mlnimise offshore sand losses for wlnd and wave climate of one ln five I years return lnterval. I I I I I I I I I I I 37 I I I I 8. Conclusions Model testing has provided a comparison between several lake configurations, which could be formed by further dredging of the existing situation at Chipping Norton. Tidal current patterns of sufficient I velocity to ensure reasonable mixing of pollutants are found to eXist In all areas of the lake scheme for one feasible lake configuration (Figure I 18) • A brief investigation Into the likelihood of stratification In the final lake configuration Indicates that deoxygenation at depth could possibly occur. Any alteration of lake boundaries will have little effect I on the problem, and no solutions are proposed at this stage. Estimates have been made of the amounts of slIt and sand that I the lake will trap. All indications are that there will be no problems associated with reduction of lake depth due to sedimentation. Maintenance I dredging of system at the headwaters of the lake will be Infrequent. Investigation has shown that bed fines presently in the system will move under tidal flows In some areas of the proposed lake scheme. Although successive floods and some freshes will tend to remove fines from I the system, clays and silts eroded upstream of the lake by freshes will be deposited in the lake, thus ensuring the continual presence of a layer of I fines on the lake bed. The stability of sand beaches on the boundary of the lake scheme has been examined, and predictions of the likelihood of sand losses I are provided. I I I I I I I I 38 I I I 9. Recommendations I It 1S recommended that a lake plan shape be adopted that has no areas of low veloc1ty during the whole of a t1dal cycle. To this effect, Configuration 6 should be adopted as a final lake plan. Deta1ls are I provided In Figure 18. Prof1les for proposed beaches 1n the lake scheme are shown In Figure 35A and B. It is recommended that the beaches be formed to these I profiles to m1nimise sand losses. It 1S also recommended that monitoring of sal1nity/temperature I prof1les be carried out, part1cularly when the lake is dredged to 8 metres. Thought should be given to artif1cial means of overturning the lake if I stratif1cat10n problems become evident. I I I I I I I I I I I I 39 I I I 10. REFERENCES I 1. Cox and Cork111 Pty. Ltd., October 1977 'Ch1pping Norton Lake Planning Study' I Report for Department of Public Works N.S.W. 2. de Vries M. 1977 I 'Scale Models in Hydraulic Engineering' Lecture Notes for Internat1ona1 Inst1tute for Hydrau11c and Env1ronmenta1 Engineer1ng I Delft. 3. State Pollution Control Commission (SPCC) I 1977 'Environmental Control of Botany Bay and its Tr1butaries' 4. Howard K. I 1973 'Contemporary Change and Prospects of the Georges River' Exercise 3 prepared for a D1p1oma of Env1ronmental Stud1es, I Macquarie University. s. State Po1lut1on Control Commission I (in preparation) 'D1sso1ved Oxygen' Tech. Report BBS 17 I 6. State Po11ut10n Control Commiss1on BBS 4 January 1979 I 'Health Aspects of Faecal Contaminat10n' 7. State Pollution Control Commiss1on BBS 11 (1n preparat1on) I 'Nutrients and Phytoplankton 1n Georges R1ver' 8. State Pollution Control Commission BBS 9 (in preparation) I 'Turbid1ty' 9. Warner R.F. and Pickup G. I 1976 'The Effects of Urbanisation, Changed Hydrologic Reg1me and Sand Dredging on the Georges R1ver, New South Wales' I 10. Metropo11tan Water Sewerage and Drainage Board Personal communicat1on March 10th, 1978. I 11. Harleman D.R.F. and Abraham G. 1966 'One-D1mensiona1 Analysis of Sa11nity Intrusion in the I Rotterdam Waterway' Delft Hydraulics Laboratory Publication No. 44 I 40 I I I 12. Harleman D.R.F. and Ippen A.T. 1967 I 'Two-D1mensiona1 Aspects of Sa11nity Intrusion in Estuaries' U.S. Army Corps of Engineers T.B.13 I 13. Department of Public Works, Manly Hydraulics Laboratory Report No. 239 August 1978 I 'Georges River Dynam1cs Study - Hydraulic Data Collection' 14. State Pollut1on Control Comm1ssion BBS 8 1979 I 'Water Movement and Sa11nity 1n the Georges R1ver' 15. Munro C.H., Foster D.N. and Harr1s G.A. November 1967 I 'The Effect of Construction of Proposed Lake at Ch1pp1ng Norton on Behav10ur of Georges River' Univers1ty of N.S.W. Water Research Laboratory Report No. I 67/7 16. State Pollution Control Commm1ss1on I 'Rout1ne Water Quality Monitor1ng - Lower Georges R1ver' 17. Department of Pub11c Works, Manly Hydraulics Laboratory Report No. 219 I December 1977 'Georges R1ver Dynamic Study - Hydraulic Data Collection' I 18. Breusers H.N.C. 1976-1977 'Lecture Notes on Sediment Transport l' I Internat10nal Course in Hydraulic Engineering, Delft 19. S1mons D.B. and Senturk F. (ed) 1977 I 'Sediment Transport Technology' Water Resources Publ1cat10ns, Colorado, U.S.A. I 20. RaJaratnam N. and Pani B.S. January 1974 'Three-Dimensional Turbulent Wall Jets' I ASCE 100 HY 1 21. Coastal Engineering Research Centre 1977 I 'Shore Protection Manual' (Th1rd Edition) U. S. A. I 22. Weigel R.L. 1964 'Oceanographical Engineer1ng' I Prent1ce Hall, New Jersey I 41 I I I 23. Hodgklns D.O. 'Numerical Methods II - Computational Hydraulics' I Lecture Notes - Int. Inst. for Hyd. and Env. Engineering Delft 24. Launder B.E. and Spa1dlng D.B. I 1972 'Mathematical Models of Turbulence' I Academlc Press, London 25. Ippen A. T. (ed) 1966 'Estuary and Coastal Hydrodynamics' I McGraw-Hlll, U.S.A. 26. Higuchi H. et al I 1975 'Tldal Residual Circulations in the Hydraulic Model' ASCE Symposium on Modeillng Techniques I San Franclsco 27. Lean G.H. and Weare T.J. January 1979 I 'Modeillng Two-Dimenslonal Circulating Flow' ASCE 105 HY1 I 28. Tebbutt T.H.Y. 1971 'Prlnciples of Water Quality Control' I Pergamon Press, New York 29. Parker, C.D. 1972 I 'Application of Water Quality Crlteria' in Flfth Federal Convention, Australlan Water and Wastewater Association I Adelude 30. Gomes Lewis I Personal communicatlon to Project Eng1neer, Chlpp1ng Norton Lake Scheme 31. N1elsen Peter I January 1979 'Some Baslc Concepts of Wave Sediment Transport' I Technical University of Denmark (Serles Paper 20) 32. BiJker E.W. and van de Graaff J. 'Bottom Friction Forces' In Massle W.W. (ed) I 1978 'Coastal Engineering Vol.11 - Harbour and Beach Problems' I Delft 33. Madsen O.S. and Grant W.D. I 42 I I I 1976 'Qualitative Description of Sediment Transport by Waves' I 1n Proceed1ngs - Fifteenth Coastal Engineering Conference, Hawai1 I 34. Swart D.H. December 1974 'Offshore Sed1ment Transport and Equilibrium Beach Profiles' I Delft Pub11cation No. 131 35. van de Graaff J. 'Modern Coastal Sand Transport Formulas' I in MasS1e W.W. (ed) (op cit.) 36. Christensen B.A. 1972 I 'Inc1p1ent Motion on Cohes1on1ess Channel Banks' in Shen H.W. (ed) 'Sedimentat1on' I A Symposium to honour Prof.H.A. E1nstein, Colorado University 1972 I U. S. A. 37. Kamphu1S J. W. May 1975 'Fr1ct1on Factors Under Osc111atory Waves' I ASCE 101 WW2 38. K1ng, C.A.M. (ed) I 1972 'Beaches and Coasts' Edward Arnold I London 39. Komar P.D. and M111er M.C. 1974 I 'Sed1ment Threshold under Oscillatory Waves' in Proceed1ngs, Fourteenth Coastal Engineering I Conference, Denmark 40. Munro C.H., Foster D.W., Nelson R.C. and Bell F.C. December 1967 'The Georges River Hydraulic, Hydro1og1c and Reclamation I Studies' Un1vers1ty of N.S.W. Water Research Laboratory Report I No. 101 41. Riedel H.P., Kamphuis J.W. and Brebner A. 1972 I 'Measurement of Bed Shear Stress under Waves' 1n Proceed1ngs, Th1rteenth Coastal Eng1neering I Conference, Canada I 43 I I I 42. Weggel R.J. November 1972 I 'Maximum Breaker Height' ASeE 98 WW 4 I I I I I I I I I I I I I I I I 44 I I I I APPENDIX A: EQUATIONS OF MOTION AND THE MODEL RELATIONS I I The model relations used in the study can be derived from the vertically integrated momentum equations. I The follow1ng treatment of the momentum equat10ns (Al to A4) is based on lecture notes (ref.23) by D.O. Hodgk1ns of the Norwegian I lnsti tute of Technology, Trondheim. Al. The Basic Equat10ns (Momentum Equation) I The conservation of momentum for a fluid is expressed by - rate of change of momentum level + = p body forces I gradient of momentum flux density One form of this relation 1S the set of Reynold's I equations - I I (Al) where t = time x,y horizontal Cartesian coord1nates I z = vertlcal Cartesian coordinate U,v = horizontal veloc1ty components w = vertical veloc1ty component p = density I p pressure v = k1nemat1c ViSCOS1ty I 't'lJ = Reynolds stress tensor arising from turbulence p'V"';'i = 1 J (time averaging applied to the fluctuating components of the I instantaneous velocity vector) There is also a similar equat10n in y (A2) I and another 1n z w1th a right hand gravity term - I = -g (A3 ) I 45 I I I These equat10ns have been time averaged over a time long w1th respect to turbulent fluctuations (u', v', w') and short with respect to I variation of the 'mean' flow variables (u, v, w). They are also slmpl1fied by neglecting density differences, I Coriolis force and wind stress. A2. Hydrostatic Pressure D1stributions I For small surface curvature, we can neglect the vertlcal accelerations, so equation (A3) becomes - I ap = - pg (A4) Tz and hence p pg ( ~- z) for zero water surface pressure I where ~ = Zat surface I A3. Integration Over Depth By 1ntegrating (AI) and (A2) from the bed to the top surface I and applying the k1nematic boundary condition - I and the bottom quadrat1c shear approximat1on - (pu'w') = I bottom I and similar 1n y, we obtain - top auh + auzh + auvh + ghah + [haii""'z + hau'v' + a J ~zd btmU Z I at ax ay ax ax ay ax + a (bau)} = 0 .. , (AS) I a y a y and slm1lar 1n y (A6) I Here the terms such as u refer to the dev1at1on from mean horizontal veloc1ty in the x direction (Figure 36). I A4. The Eddy V1scosity Approach It 1S now accepted that the Reynold's stresses can be I approximated by the Boussinesq relat10ns u' J = -K .2.!! I l1ax ;-;;; -K au = Uay I 46 I I I etc. where the I's are coefficients of eddy v1scosity which can be expanded to 1nclude the terms 1nvolv1ng depthwise deviation from mean I hor1zontal velocity, i.e. I hau' a + a f~adz = -1* haau I ax ai 11 ax a ha u' v' + a f uvdz,." = -I * ha3v 12 ayr I ay ay Hence equat10ns (AS) and (A6) reduce to I I - v [ a (ha u) + L ( hiU!.) ] o ax ax ay ay ••• (A7) I and s imil ar in y ••• (A8) I AS. The Turbulence Model Accordlng to Launder and Spaulding (ref. 24) the most appropriate models of turbulence for free turbulence are those which I O express 1 11 ,112 , etc. as a proportion of k 51, where k 1S the kinematlc energy of turbulance and 1 is the length scale of turbulence. I The closure of the problem can be affected by relating k and 1 ln transport-type equatlons (ref. 24)- I D(kl) - a (koqakl) = o . 9 8 k o· S p ( au P - o. 0 S 9 k 1 5 ••• (A9 ) I Dt ax h ax I Dk Dt ••• (AI 0) I Here~represents total dlfferentlation ak + kak Dt at at I These equations are simplifled and one dimenslonal, but can be used to yield the scale relations. I I 47 I I I A6. Similarity Relations In order to avoid scale effects, each term in equatIons (A7) to I (AlO) must have the same scale (ref. 2). The similarIty relations can be obtained by comparing terms I within the equatIons, e.g. I i.e. • •• this is a scale law which must be I upheld Other relations are scale conditions, which mayor may not be I satIsfied dependIng on their Importance on the phenomena being studIed. The following table lists the relations that are obtaIned. I I I I I I I I I I I I 48 I I TABLE Al I Terms Similarity Relation Law or Condition auh • ur> = XR/tR law I at "' v law I R = YR/tR • ghah u I(g ~)O$ = 1 Froude condition !FR = R R I ax au~h • v L( hau) = u h Iv = 1 Reynold's condition •• R R R •• I ax ax ax auh • Ku(u~+v~)O$ n = x I~ = 11K., roughness condition I at (n =mo~el distortion) au~h • K. ha~u KilR = ~XR eddy coefficient turbulence I ax 11 ax~ condition auvh • K. ha~v KhR = ~YR eddy coefficient turbulence ay 12 ay~ condition I au o .059k1·$ k 0-$ = u kinetic energy turbulence • R R at condition I L(ko'$ lakl) • lR = X mixing length turbulence ax ax R condition o .98ko'$ 12 (au) ~ I ax I •• The length scale in the Reynold's condition has been shown to be most appropriately I LR = ~ for wide flow areas. I I I I I I 49 I I I APPENDIX B: MODEL SCALES AND MODEL CAPABILITIES I The model scales were chosen on the basis of the requirements I to s1mulate the phenomena of importance, with the constra1nts of ava1lable area and funds. I Bl. Hydrodynamic Requ1rements The hydraul1c behaviour of the lake is not s1mple, so I considerable care had to be taken in choosing scales and interpret1ng model results. I There were five large scale flow s1tuations that could exist in the lakes (F1gure 37) - I (i) Expansions and contractions, (11) Circulating flow 1n a side bay, I (iii) Circulating flow w1th little or no solid boundaries, (iv) The main flow paths between f1xed boundaries, I (v) The main flow paths between moveable boundaries (eddies). Although the mechanisms for these motions are not completely I understood, 1t 1S thought that the princ1ple of conservation of momentum must be satisfied throughout the flow field. The following set of similarity relations was derived in Appendix A from one form of the I momentum equations (the Reynold's equat10ns). I B2. S1milar1ty Relat10ns I = 1 The Froude condit10n states that the relat10n between inertia and grav1ty I is 1dentical 1n model and prototype. I =1 The Reynold's condition states that the relat10n between inert1a and I viscous forces 1S 1dentical in model and prototype. I I 50 I I I The model roughness is flXed by the distortion. u x IR* = R R =1 I R K* llR This is slmilar to the Reynold's condition, except that the horlzontal eddy I ViSCOSlty replaces the kinematic vlscosity. ThlS condltion can be replaced by two conditions concerning fundamental characterlstics of the turbulence I structure. The kinematic energy turbulence condltion states that the I turbulent kinematlc energy is scaledldentically wlth the mean kinematic energy. I The mlxing length scale should be the same as the horizontal I length scale. (There is a similar relation in the vertical directl0n.) I B3. The Froude Condition For free surface flows, the Froude condition should in general I be satlsfied. The resulting relatl0ns between veloclty, flow, time and linear scales are - I = I = 1 ~ ~hrR .. hR "XR X X h-o.s I tR = R = RR ~ I B4. The Reynold's Condition and Vertical Scale The Reynold's condition need not be satisfied if the V1SCOUS terms ln the momentum equations are relatively small. ThlS generally I occurs when m > 2000 In the prototype, ~ ~ 5 X 10 5 I The 11mlting Reynold's number can be used as a gUlde to I choosing the vertical scale. I I 51 I I I I h 15 -!-- I V R = (IR v ) 6 7 = IRR 67, if the same viscosi tv appl ies R R to model and prototype I So = (LLI0~167 40 2000 Another gU1de to the cholce of vertical scale for tidal models is given by I Ippen (ref. 25) where T is the tidal cycle I p T = X p 4.6 10· seconds h 4 to 8m p I Z v 10 -6 m / s Based on these considerations. a vertical scale of 50 was I chosen. I B5. The Horizontal Scale The horizontal scale of 250 was chosen based on three I considerations : (i) The area avallable under cover was limlted. If the model were not protected from the wind. there would have been severe restrictions on the I tlme suitable for operation. (li) Ideally the model should be undistorted. Practlcally. the model should be as little distorted as possible. A distortlon greater than 6 I would be unacceptable. I (iil) There was a cost restrictl0n. B6. The Roughness Condition I The fact that the model was distorted means that the model bed should be roughened to correct the water slope. I B7. The Turbulence Conditions It was anticipated that the main driving force for the large I scale eddies would be turbulent shear. caused by transverse velocity gradients. Correct modelling of this phenomenon lS assured lf the eddy coefficient turbulence conditions (or the kinetic energy and mixing length I turbulence conditions) are satisfied. I 52 I I I According to Higuchi et al (ref.26), a suffic1ent condition for satisfying the turbulence conditions is that Reynold's numbers are h1gh enough (1.e. m 1S 2000). Under closer exam1nation Lean and Weare (ref.27) I deduced that 'the only situation in which the distorted model will reproduce circulating flow correctly is when shear layer turbulence I dominates the m1xing in both nature and the model'. Rough l1m1ts were given as follows : I (i) Shear layer mixing will dominate secondary currents when - ~ h > I ( ii) Shear layer m1xing w1ll dom1nate bed-generated turbulence when : ~ < ~=- I h g where g gravitational acceleration C = Chezy roughness coeff1cient I L length scale of eddy~ radius of eddy h = water depth I In the prototype, C T' 60 L T 100 m I h 8 m Hence - ...!...= 12 .5 £.: 370 I h g J....= 12 .5 2508°5 13 I h C So the conditions are almost satisf1ed. I In the model : C 60, L = 0.4 m, h = 0.16 L = 2.5 ~ 370 I 11 g .....k = 2.5 25013°5 = 13 I h C This indicates that the secondary currents will tend to dominate the effect of shear in the model, unless the model is smooth to a I Chezy C of 300 (not possible) or the model was undistorted (again not possible for other reasons). I B8. Model Capab1lity Based on the above theoretical considerations, it appeared that I the model could be used to - I 53 I I I estimate flow patterns and velocities in the main stream I areas, (ii) 1dentify regions of low or zero velocity, I (i11) gauge the effects of changes in lake conf1guration on the first two items. I It could not be used for (iv) estimat1ng flow patterns and velocities in eddies or side I bays, !I (v) determining vert1cal velocity distributions. However, model verification showed that eddy velocities and flow patterns were being more accurately modelled than theory suggested. I I I I I I I I I I I I I S4 I I I I APPENDIX C. EQUIPMENT DETAILS Cl. Pumps I 0) Georges River - 'Alpha' self-priming pump 1nlet 2" dia. flanged outlet 1.5" dia. female I screwed - Motor Webster 240V 1.5 HP I 2850 RPM. (1i) Prospect Creek I - "Onga" model No. MC15 : inlet I" female screwed outlet I" female screwed I c/w Motor 240V 0.33 HP 2800 RPM I C2. Flow Meters - S1ze 25 1ndustrial brass 'Gapmeter' supplied by Duff and I Maclntosh, Sydney I - Range 8 - 80 L/min water at 20 GC - Connect10ns : female screwed I" BSP. I C3. Water Level Followers (Vibrating Tip) These instruments follow the water surface to an accuracy of I 0.1 mm and provide a continuous digital readout throughout each test. The signal is amplif1ed to drive a servo motor, which propels the tip up or down depending on the water level. The problem of formation of a meniscus I is overcome by havlng a vibratlng tip half in and half out of the water. A mean value 1S then recorded. I C4. Sti11 Camera Pentax ME : 35 mm full frame SLR camera wlth automatic I winder, timer and cable release for t1me exposure. I Lens 28 mm focal length, speed 2.8 Fil ter Hoya Skylight (18) I Settings f stop - fl1 (f16 towards the end of the I 55 I I I series) I shutter speed - B setting (time exposure) auto-winder s (single frame) I Ilford PanF I Fine grain Black and White 36 exposure, ASA SO CS. Mov1e Camera I Pa11lard Bolex 16 mm movie camera, manually wound, with timer for time-lapse filming I - Lens focal length 16 mm, speed 2.8 Settings f stop - f2.S I : height 9 m (upstream end of the model) 5 m (downstream end of the model) I C6. Flash Unit - Braun FSOO : power pack with two flash heads. (Repeated I failure of this unit necessitated replacement in February 1979.) Power Source: Ma1ns. I - Metz 'Mecabl1tz 402' power pack w1th one flash head Illumination 600 horizontal, 46 0 vertical I Power source Standard 6V lead battery I C7. L1ghts I - Phil11ps 'Argaphoto BM' 2S0V, SOOW Number 14 I He1ght 4.5 m above model I CS. Electron1cs (i) Pentax Shutter Timer (Refer Figure 3S) : Operation On closing the tr1gger switch, the variable pulse generator I opens the shutter by energ1s1ng a solenoid that pushes a cable release connected to the camera. The shutter is held open for a time that can be preset by an external control. At the end of th1s time, the shutter is I closed and the I-second pulse time is triggered. Th1S operates the motor I 56 I I I winder which advances the film and cocks the shutter. A t1me exposure of 15 seconds was adopted for recording drogue movement while testing. I (ii) Bolex S1ngle Frame T1mer (Refer F1gure 38) : Operation: The frame rate is determined by a slow running osc11lator that has two selectable rates, one pulse every 3 seconds or one every 5 seconds. I This pulse is used to tr1gger a pulse generator wh1ch has an adjustable pulse length. This time controls the 'pull in' time of the solenoid used to move the s1ngle frame control of the mOV1e camera. The latter rate of I one frame every five seconds was used to record the tests. I I I I I I I I I I I I , , I I 57 I I I I APPENDIX D: MEASURES OF POLLUTION I Most of the informat1on contained in th1s Appendix was supp11ed by the State Pollut1on Control Commission (SPCC) (ref.16) with some I add1tions obtained from references 28 and 29. D1. Dissolved Oxygen I In r1vers and estuaries oxygen dissolved in water comes from the atmosphere, plant photosynthesis, and from exchange with the ocean water. Decomposit10n of organ1c matter consumes oxygen and, unless it is I replaced at the same rate as it is removed, reduces oxygen levels to less than saturation. Dissolved oxygen concentration is one of the most important I 1ndicators of water quality, because it is the qua11ty factor which is most readily 1mpaired by b10degradable organic matter, and because an adequate level of oxygen is essential for the maintenance of the diverse life forms I wh1ch normally exist 1n natural waters. F1sh and invertebrates are sensitive to low oxygen I concentrat10ns and levels below 60% saturation. Oxygen levels can be super saturated due to plant photosynthet1c activity, which releases oxygen during daylight hours. These values may fall to low levels dur1ng the hours of darkness, when this activity ceases and oxygen is consumed dur1ng I resp1ration. These large diurnal var1at10ns may upset aquat1c life. There are no absolute criteria for assessment of water quality, I but it is des1rable that oxygen as percent of saturat10n should be in the range 65-110. I D2. Faecal Coliform Bacteria Faecal coliform bacteria (E. coli) are the most re11able I 1ndicators of possible pollution by sewage, notwithstanding the l1mitations accompany1ng their estimation. E.coli are not generally considered to be pathogenic. Indeed,they are part of the natural flora of the intest1nes of I all warm- blooded animals, occurring 1n faecal matter in the order of 100 to 1000 million organisms per gram. The organisms deriving from man cannot be distinguished from those deriving from animals. E.coli can be expected in many natural waters and do not necessarily mean pollution by human I faecal matter. The results of the determination of faecal coliforms 1n waters must be interpreted in the light of the persistence and magnitude of I recorded levels and the likely sources from wh1ch the organ1sms may derive. Results are reported as faecal co11forms per 100 m1ll1litres. I The following levels are suggested for faecal co11form : I 58 I I I Swimm1ng Dr1nking I o - 5 counts/100 ml- good 0 counts/100 ml- excellent 50-500 - doubtful l~ - satisfactory >500 - poor 4-10 - suspicious I >10 - ~satisfactory The SPCC standard for bathing beaches near ocean outfalls is set at 200/100 I mI. D3. Nutr1ents I Overseas studies have demonstrated the signif1cance of the roles of nitrogen and phosphorus in stimulating plant growth, although they I are only two of a number of essent1al elements. The major sources of nitrogen and phosphorus arise from human act1vit1es and the term 'cultural pollution' has been coined to describe I this. Sewage effluents, urban and agricultural run-off, and some industrial discharges all contribute major loads of these nutrients to water systems. I Nitrogen and phosphorus have quite different mobilities in an aqueous system. Nitrate-nitrogen moves rapidly as it is not readily complexed, 1ncorporated into organ1c compounds or adsorbed by sed1ments. I However phosphate-phosphorus is practically immobile. It is able to form strong complexes, is readily adsorbed into sediments and is quickly incorporated into organic compounds. I Most plant growth problems ar1se in relatively still waters. Under these cond1tions rapid growth can occur and g1ve rise to many water quality problems. These may be restrict10n of flow, high oxygen demands I created by decaying plant material, large changes in oxygen levels due to photosynthesis changes in light and other associated parameters. Each of these has a significant impact on water qua11ty in terms of hydrology, I water chemistry and the aquatic b10ta. The nutrient used in this study is one of the nitrogen forms - I ammon1a (NB3). N1trogen exists in waters as ammonia, n1trites, nitrates, ammonium compounds, and bound in organic compounds. Ammon1a and n1trites I are most l1kely to occur in poorly oxygenated waters and nitrates in well aerated waters. with phosphorus, n1trogen which may be released from I sediments 1S an important source in the nitrogen cycle. Plants usually ut1lise nitrogen 1n an organic form but bacteria are able to break down organic nitrogen compounds. Some algae, notably the I bluegreens, are able to fix nitrogen directly from the atmosphere. N1trogen is routinely analysed as total n1trate and nitr1te, I ammonia n1trogen and albuminoid n1trogen. I 59 I I I Some relevent levels for NH3 are as follows )40 ~g/l detectable by smell I (100 potable 1000 unsatisfactory level I D4. Blochemical Oxygen Demand (BOD) The bl0chemical oxygen demand is a measure of the amount of I oxygen consumed under aeroblc condltions during an Incubation of a water sample under standard conditions. The incubatl0n IS conducted at a constant temperature of 20°C over a given period, usually five days. It I measures the amount of oxygen required for the bacterial breakdown of organic material present In the sample. Under natural condltions, organic materlal In streams is continually biologically degraded and oxygen IS I requlred for this process, but this demand rarely causes an oxygen deficit. Occasl0nally natural phenomena will create large BOD, but these more usually arise from pollutant discharges such as sewage treatment works I or food processing plants. Relatively unpolluted natural waters have a BOD In the range O.S to 3 mglL, whilst BOD values greater than thlS suggest the presence of organlc polluting matter. Raw sewage has a BOD of 200-400 I mg/L. \ I DS. pH pH IS the reciprocal of the common logarithm of the molar hydrogen 10n concentration and IS a measure of the Intenslty of aCldity or I alkallnlty of waters. The pH scale ranges from 0 to 14 w1th values above 7 indicating Increaslngly alkaline conditions and values below 7 Indlcating increas1ngly I aCldlC conditlons. The pH of seawater is almost invariably constant at 8.2. In fresh waters, pH var1es in the range 6.0 9.0, 1tS value depend1ng upon the qUlte complex equil1br1um which eX1sts between a number I of 10nic speCles found In natural waters. Large changes in pH usually Indicate the occurrence of I pollution, wh1ch may arise from, for example, industrial discharges or even from algal blooms. During photosynthes1s, algae use free carbon dioxlde and also extract some carbon d10xide from bicarbonate ions. This results I In increased hydrolysis and thus an increase in pH. Although pH may not always be a s1gniflcant water quallty parameter, it does frequently glve a clue to other factors that may be I slgnificant. I D6. Turbidity Turbldity is a measure of light absorpt10n and scattering by suspended sollds, but the relationsh1p is not necessarily s1mple nor I constant. Turbldity is dependent on the nature of the materlal in I 60 I I I suspenSion, its size and its shape. Turbidity occurs in natural waters through the presence of I plankton, organic and inorganic matter, silica, clay and silt. Agricultural runoff, construction activities, industrial discharges, extractive industries, stormwater runoff and municipal wastes may contribute heavlly to increasing turbidity of water. The effect of I excessive turbidity is most obvious as a reduction in water transparency and its associated loss of aesthetic appeal. In addition, turbidity reduces light penetration, affects the temperature of the water, and has I important consequences on the availability of food for aquatic life. I The results are reported as Formazin Turbidity Units (ftu). Typically the level of turbidity ranges from 20 to 200 ftu in rivers. In the Georges River the base level is about 20 ftu. 20 ftu is about the upper level for potable water, although well treated water should I have a turbidity less than 1 ftu. I I I I I I I I I I I I 61 I I I I APPENDIX E: BEACH STABILITY CALCULATIONS I E1. Des1gn Conditions Following completion of model test1ng, effective fetches were calculated uS1ng the recommended lake configuration for all proposed beaches in the scheme. Using shallow water wave forecasting curves in I reference 21 with a wind speed of 64 km/hr provided design wave heights and periods for a recurrence interval of approximately once in five years I (ref.30). This informat1on is shown for each beach 1n Table El. TABLE E 1: DESIGN DATA FOR BEACH STABILITY INVESTIGATION I Position of Beach Effective W1nd Sig. Wave Sig.Wave Fetch Direction Height Period I (km) H (m) T (s) Northern bank, near 0.72 S.S.W. 0.43 2.30 I Georges River Road Beach near Charlton 0.64 N. 0.41 2.25 I Avenue Wildhfe Island 0.60 W. 0.40 2.20 I Chipp1ng Norton Bay 0.50 N.E. 0.37 2.05 I Georges Hall Bay 0.42 S.S.W. 0.35 2.00 Beach near Hollywood 0.40 W. 0.34 1.90 I Drive It was decided to adopt Mean Low Water Neaps RL 99.76 m as a design water level, wh1ch gave a minimum water depth for safety reasons for I estimating bed shears at 2.46 m at the beach toe. I E2. Initiation of Motion A good coverage of the field of wave sediment transport can be I found 1n Nielsen (ref.31). The follow1ng treatment (sections E2 and E3) is taken from th1s I pub11ca hon. An examination of the forces acting on a sand particle under the effect of an oscillatory flow reveals that the forces due to pressure gradients and accelerat10ns in the fluid are negligible compared with drag I forces, which are analogous to those in steady flow. I 62 I I I Th1s ind1cates that the Shields criterion app11es as well to oscillatory flow situat10ns as it does to the steady flow case. Minor adjustments which affect the dimensionless parameters are required, notably I using ~', the shear stress corresponding to grain roughness, rather than total shear stress. From a Shields D1agram for horizontal bed, use can be made of I those factors given in reference 18 to derive a Shields Diagram for a sloping bed. The results of th1s exerC1se are shown in Figure 34, which shows curves to pred1ct initiat10n of sediment motion for a horizontal bed I and a bed of slope 1:3. The ordinate of the graph 1S a measure of dimensionless shear I stress - ~o I (ys-yw)D where the bed shear stress (y s-yw) (ps-pw)g = l.65KlO· for sand. I and D the mean gra1n diameter of the bed material. I The absc1ssa measures the shear Reynolds number U. D/v where U. 1S the shear velocity (~O/p)05 and v is the k1nematic viscosity of the fluid I (v = 10-& m2 s -1 for water at 20 G e). A value of bed shear plott1ng above the curve indicates that I the shear 1S above the critical value for that particle grading, and movement will be likely. I E3. Bed Shear Stress Under Waves Ignor1ng phase differences, and using a maximum value of the I instantaneous shear stress, the maximum shear close to the bed is found from : I ~omax = 0.5pfw(Uo)~ (El) where the maximum water velocity is g1ven by small amplitude wave theory I 1 sinhkh I The friction factor fw can be found for the turbulent case from the following equation, or from graphs in ref.32 I fw = exp [5.213 (r/ao)~1'. - 5.977] (E2) where ao is the horizontal water particle displacement near the bed, and r is the bed roughness. The above formula is valid for 1.47«ao/r) I <3000. For ao/r ~ 1.47, fw has a constant value of 0.32. I 63 I I I The bed roughness is highly dependent on the bedforms present, and few references gave definite recommendations concerning reasonable values of r. I Nielsen states that 'under waves it appears that the concentration of moving sediment is related more closely to the skin friction 't' than to the total shear stress' • !tis therefore assumed I tha t 't' is independent of the bedforms, and a value of r equal to 2.S L times the median grain diameter is reasonable. 7 - Calculation of the non-dimensional Shields Parameter I corresponding to grain roughness - I S' = 'to'max (ys-yw)D I follows from equation (E1) using fw from equation (E2) with r = 2.SD. The calculated value of 9' can be entered into the Shields Diagram, as outlined in section E2, to determine the likelihood of motion of the bed material. I Sample calculations are included in section E6. I E4. Bed Shear due to Tidal Currents The choice of equation to represent the velocity distribution I Vz under uniform flow is determined mainly by two factors : (i) the nature of the flow, and (ii) the nature of the boundary. I For laminar flows, a parabolic velocity distribution is suitable, whereas for turbulent conditions a logarithmic profile is adopted. The transition laminar-turbulent flow in an open channel is I approximately I It = 2000 This value is exceeded during most of the tidal cycle so a I logarithmic distribution will apply. The bed roughness will determine the point where Vz 0 according to the logarithmic profile. Ripple formation for values of 9' I between 0.04 and 0.2 for a horizontal bed can be expected (ref.31). Since bed motion is theoretically being avoided, a smooth bed is assumed and a roughness value of r = 2.SD is adopted. The following formula applies for I a logarithmic velocity distribution for uniform turbulent flow(ref 18) : Vz = (V./V)ln(ZIZo) where Zo = distance from the bed at which the velocity I is zero according to the logarithmic profile K = Von Karmen constant = 0.4 I The value of Zo is of the order of 0.1 Y IV. for a smooth bed and r/33 for a I 64 I I I rough bed. Being dependent upon shear velocity for the case of a smooth bed, Zo must be calculated by tr1al and error 1n th1s case. If the latter value of Zo is used, the calculations are s1mpler and little accuracy is I lost (see section E6). Hence the veloc1ty d1stribution is given by- V(Z) • (V*/K )In(31Z/r) (E3) I Equation (E3) can be solved for v* shear veloc1ty and hence shear stress for use in a Sh1elds D1agram to predict the l1ke11hood of I movement of bed mater1al. Calculations are prov1ded 1n section E6. E5. Bed Shear due to Wave and Curent Combination I For pred1ction of bed shear due to a comb1nation of waves and currents, resultant veloc1t1es for each component must be determ1ned at a I height Z' above the bed, where - Z' = e Zo (e - base of natural logarithms) (ref.32) I Shear stress at Z = Z' 1S accepted as equivalent to shear stress at the bed. Veloc1ty profiles are shown in F1gure 39 for orb1tal velocity and un1form flow. I Figure 40 shows resultant velocit1es on the plane Z = Z' for wave crests approaching a constant current under an angle, • From vector I addit10n: the resultant veloc1ty 1S simply - Vrz' = (Vz'~ + Uz'~ + 2UZ'Vz's1n,)OS ••• (E4) I with shear stress d1rected along the time-varying line of action of Yr. Der1vation of Uz' is given by B1Jke and van de Graaff (ref.32), wh1ch prov1des an alternat1ve equation to (El) 1n section E3 for bed shear I stress under waves. It 1S assumed that the actual water velocity 1n the wave at an elevation Z' above the bottom is g1ven by - I Uz' = p.Uo (E5) This g1ves an equat10n for shear at the bed of the form - I (E6) "PI' = pK~(p.UOP I By comparison w1th (El), 1t can be seen that - p = 1(0.5fw)OI (E7) I K (Addit10nally the max1mum value of p physically 1S ,1.00, corresponding to fw = 0.32 as given in section E3.) " '. I One major obstacle 1S the determ1nation of a friction factor fwc for the comb1nation of waves and currents. Th1S problem is unresolved to date, although some authors recognise it as a problem. The friction I factor for pure wave mot10n can be an order of magnitude larger than the I 65 I I I factor for a current of comparable magnitude (ref.33). In the absence of further information, a value of fwc equal to that found for fw in the wave only case will be adopted, as g1ven by equation (E2). The derivation of I Vz' follows from the procedures outlined 1n section E4. With z Z' 1n equation (E3), where Z' = er/33, we obtain I Vz' = V*/K (ES) I Hence knowing the shear velocity V* for a given velocity profile [found from equation (E3»), the velocity at a height Z' above the I bed is s1mply obtained. Using an equation of the same form as equation (E6) for the I combined wave and current situation Y1elds - ~wc = pK~(Vr)~ at depth Z' I = pK~(Vz'~+Uz'~+2Uz'Vz'sin~) = pKS(Uz')S[(Y.!..')~+l+2(y!"')Sinq,) I Uz' Uz' where pK~(UZ')Z is the bed shear under waves only Reorganisat10n of the above gives the 1ncrease in bed shear as I given by Swart (ref.34) I ~ w c / ~ w = 1 + (V z ' / U Z ')2 + 2 ( V z ' / U z ' ) s 1 n,. • • (E9) Equation (E9) g1V~S a max1mum value of ~wc uS1ng the ampl1tude of the orbital· velocity under waves. Phase differences are of no consequence I here. Mean values of ~wc for a wave period have been calculated by I van de Graaff (ref.35) for bed transport prediction, but as we are interested only 1n the prediction of 11kelihood of sediment mot1on, the I maximum value prov1ded by equat10n E9 will be of use. I I I I I 66 I I I I E6. Bed Shear Stress Calculation (a) Beach Near Hollywood Dr1ve I Data: Hs = 0.34 m T = 1.90 s h 2.6 m at toe I D50 = 0.3 x 10-1 m • Shear Under Waves I h = 2.6 0.4617 Lo 1.56 x (1.90)~ I From Table C-1 of reference 21, sinh(kh) = 9.2243 From 11near wave theory, the max1mum horizontal water particle displacement I near the bed is given by ao = -=-----,----,.H 2 sinh (kh) I ao max 0.34 2 x 9.2243 ao 0.018 m The amplitude of the water velocity just outside the boundary layer is then I found from - Uo max = 271ao I T = 0.061 m/s I To allow for underestimation of horizontal velocity by Linear Theory for steep waves in shallow water, this value is increased by 10%. I Uo 0.067 m/s The wave friction factor fw is given by (E2) above, where the I bed roughness r 1S taken as 2.5D. r = 0.00075 m I Hence fw = exp [5.213(0.00075/0.018)001'. - 5.977] I fw 0.042 I From (E1), the maximum shear stress near the bed is ~'w = 0.5 X 103 x 0.042 x (0.067)~ I ~ 'w = 0.094 Pa I 67 I I I I The shear veloc1ty 1S given by - I I 0.010 mls In order to pred1ct the like11hood of mot1on at th1s value of shear, the following factors are required for use in a Sh1elds Diagram, as out11ned in I section E2 : Dimensionless shear stress e' = 0.019 I Shear Reynolds Number U*D = 3.0 v The Sh1elds criter10n 1nd1cates that both a hor1zontal bed and I a 1:3 sloped bed will be stable at this level of shear stress under wave action. (See F1gure 34.) I • Shear Due to T1dal Currents Mean t1dal velocity at surface = 0.14 mls (for flood tide). I From equation (E3) - I 0.14 = (V*/0.4)ln(33 x 2.6/.00075) V* 0.00481 mls I L ,;'v = 0.023 Pa and e' = 0.005 No movement of bed mater1al at th1s depth 1S expected. Peak I veloc1t1es in a t1dal cycle could be as h1gh as say 2.5 x 0.14 = 0.35 m/s. At th1s velocity, bed shears at the toe of the order of 0.145 Pa will exist (e' = 0.03) and some sand movement down the 1:3 offshore slope can be I expected. It 1S felt that since the durat10n of this event is short, design for peak t1dal flow 1S unreasonable. The conclusion, therefore, that the profile for the beach near Hollywood Dr1ve is stable for tidal I flows, 1S a reasonable one. A check on the roughness assumpt10n made (see section E4) is I now requ1red. For Zo = r/33 as adopted here, the term In(Z/Zo) has a value of 11.647. I If the smooth bed equation were used, the term would have been I In(Z!O .01&) I I 68 I I Using the derived value of V. = 0.00481 m/s. this term becomes I 11. 736 1.e. 0.14 = (V*I.4) x 11.736 I ThlS gives V* = 0.00478 as an inltial solution. By repeating the trial and error calculation. a value of shear velocity V. of 0.00478 is found to satisfy the equation. The error in I using the simpler method for this case is therefore less than 1~. and use of the rough bed equation is warranted. I • Shear Due to Wave and Current Combin~tion Amplitude of orbital velocity at Z' above bed I From equation (ES) and (E7) - Uz' = 1.( 0 5 f ) 0·, U I K • W • 0 I = ~ (0.5 x 0.042)~S x 0.067 Uz' = 0.024 m/s I Current veloclty at Z' above bed From equation (E8) - I Vz' = V* K I where V* was found to be 0.00481 m/s. I Vz' = 0.012 mls From equation (E9) with the angle of incidence 20 0 • I ~wc/~w = 1 + (0.012/0.024)~ + 2(0.012/0.024)sin20o I ~wc = I.S9~w where ~w was calculated previously as ~W' to be 0.094 Pa I ~wc 0.15 Pa 9'wc = 0.03 I U*D = 0.0122 x 0.0003 = 3.66 v 10-6 I The Shield's Diagram indicates that this value of shear 18 I 69 I I I close to critical for a 1:3 slope. Motion of bed particles on the offshore slope will result for any increase in tidal velocity or signifi~ant wave height. The recommendation for the beach near Hollywood Drive of 2.6 m I depth of water at the toe is based on the above analysls. I (b) Beach on Northern Bank of Chipping Norton Lake near Georges Rivec Road Data: Hs = 0.43 m I T = 2.30 s h = 4.0 m at tOE; I D = 0.3 X 10-' m • Shear Under Waves I USlng the same method as the previous example h = 0.4847 I Lo Table C-l of reference 21 gives sinh(kh) = 10.634 I Maximum horizontal water particle dlsplacement near bed: ao = 0.020 m Amplitude of water velocity Just outside boundary layer : I Uo 0.061 mls Wave friction factor (for r = 2.5D) I fw = 0.040 Maximum shear stress near bed I T'W 0.074 Pa I 9' = 0.015 - stable for 1:3 slope • Shear Under Tidal Current I Mean tidal veloclty at surface 0.10 mls (flood tide) V· = 0.00332 mls I Shear stress due to mean tidal currents - I T'V = 0.011 Pa 9' = 0.002 - stable for 1:3 slope I • Shear Due to Wave and Current Comblnation Amplitude of orbltal veloclty at Z' above bed I Uz' = 0.222 mls I 70 I c c I I Current velocity at Z' above bed Vz' = 0.008 m/s With angle of incidence 90°, i.e. tidal current opposing the direction I of wave propagation: ~'wc = 1.86 x ~'w I ~'wc = 0.14 Pa 9'wc = 0.027 U~D = 3.52 I -V- I The Shield's Diagram for a 1:3 slope suggests that bed material at the toe will be marginally stable at this level of shear stress. I The recommended toe depth for the beach on the northern bed of Chipping Norton Lake is therefore 4.0 m, i.e. at RL 95.8 m. I Recommendations for the other beaches in the lake scheme were provided by calculations similar to the above. A computer programme was developed (programme BDSHR) to facllitate the calculatl0n of bed shears for I the three design combinations of waves and steady current. I I I I I I I I I I 71 I f~~~"';'~':"";:-;; '>~:;""~~" ~:!"';;i" ':-' 12 I I I I ~.~. ~ ~ ~::~/l:~~f~~~S}f~it;:~·.~ ~· f:: . "",;t\'".•. I:.'.: . ':.' "a _ ·_.,:!:-::;;~ ..... ". •._ ~·..... \ :;:~~r~4:;-~!.:..:i.J~·i6.;r;.~it·,·· :;" .~ ··· :'.~..:';: 7,1 1 \\J ~y 6'~1-~A-h~~~2f*~~~¥.f¥fhYif}~'(f---t . -l." ~'" ~' ..-~.:.':.'c-' "';'i-'!'r! fl ... , - I-. '~:"'IT~" A~;!, ;.; ;-':::;:':;::';':.... ~ .',',·:';:";·;:i<',::; .. \ .... ., "~"-:'k Z ';31 \~ ~UPf=di". . *111 I I..1 1 1 1 1 1 1 1 1~ '"0 1 r~~·'?-t?4'i/:Y: ?b.t~jh'::. ,,:11%E~:.;.;:~.:: &~ I \1 \ 1\\\ I I :H I I I I I . 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""~~~~ .is' e ;; CHIPPING NORTON LAKE MODEL - LAYOUT OF EQUIPMENT ~ II il , il ~ ,I ~6' ,I ~ \g. I ELOCITY il ~ ¥ Approx 0 5m/.l to6m /s 8/ (from metering) I Qj. ct; rY ~ I 0 EPSOM ROA I I A. FLOAT TRACKING I I I I 04 LOCITY ~; ~ Approll 0 ., M /0 I a round loland a. I ,0" I I I B. VERIFICATION OF MODEL I I Figure 4. ------ Model flow Prototype flow • Correcf· tide at model scale 11m m·l. Simulated tide 120 100 60 I 10 a o o 60 o o ...J o 40 I&. ...J I&. 2 20 Model time (minutes) A pproll. Prototype time (hours) 20 40 III III 80 1&1 III III 1&1 80 - 100 _. IC" c: SIMULATION OF TIDAL FLOW $... 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I - 200 0 I : '-:: ..J - '- Unsot.toctory Ii". it I ""=\. 1000 '00o~ : I Dr Inkin. _or ".. , • I I I I o '... '''''''',. IIZI) '''5'"1'1''Il0l111, 1'2'3 .. !lie'?" 'IKJU 12 liZ 'I.~I .,,,,,IIOtIIi "21,14""" I 11""~3 I • """tTll • lIZ tr, '''''''01''0'''",,", I q 1314'1'e 17 '!IOtI1 I 1971 1972 1973 1974 197~ 1976 1977 1971 I NH, I 10 - • - - - I ..J ' '- 0 - ""E - -If 1.,_-- _I. I II I I I II I C1tI't2 jla'S'4 ~ '6'7 • ""11112 I In'.'!!'6'7', t"tO"11 "."" .,.IT' •.,,,,, .. "2 3'41, • 7 "., IIPr; "2" ..." """",0: "''3'' ., .. n'""",.. , , ... '."101" ...... ,,'. .'.1971 1912 1973 1974 19n 1976 1977 1978 I B.O.D. WATE R QUALITY PARAMETERS From SPPC(ret 16) Figure 19A I I '0 - I •- - X.. • - I BOli c T Neutrol , -- Acid I I I II jj2 • 2' .lOf.l1, • ...", ..... "'...... 11. '"'1>1 ... I • ·ltllQlI,2 • ''''.. , ... ",.,. . • ,lOB. "... '''" • 2 ".,... II' 'IQI'" "... 1..... ". • ,.".,._"1: 1971 '97'2 1973 '974 197~ '976 '977 I pH Field' I I £ I I TiN (",on1". I TURBIDITY I I I I I I ·1 I I WATER QUAUTY PARAMETERS Figure 19B I I I E I E I I I I I E I E I I RAINFALL - Day prior to data collection I I I I E E I I I RAINFALL - Total of five days prior to data collection I WATER QUALITY PARAMETERS Figure 19C I I 13000 I ® I 12000 , o o Lowest measured DO between I liverpool and Mllperra Bndges 11000 I ~IOO 00 -z I 0 i= I 0 4000 ~ I 0 I 3000 I I I SEASONAL DEPENDENCE OF DISSOLVED OXYGEN I Figure 20 I I I 500 I ® =HlghQst recorded colli form count between o liverpool and Mllperra Bridges I 450 o o I 400 I I 350 0 0 0 300 regression line I (0) y= 16 3-~18 X 0 0 0 «> <1> I <1> 250 (1) (1) E <1> 0 0 <1> Q <1> I "- <1> ~ ® -a~ 200 0 0 I u <1> 0 (!) 0 I ...J 150 I ® 100 I I 050 I ooo+------,------~------~------._------~------__, 1971 1972 1973 1974 1975 1976 1977 I TIME (YEARS) I COLIFORM - TIME RELATION I Figure 21 I I I 500 I 450 I 400 I I 350 I Regression Ime y = 2·6 + 0 017 x 300 I (1) E S 250 (1) I "- (1) 1: (1) 0 u" ~ (1) I 0 200 Gl (1) -.g u 0 u I ....8 e 150 I!)e I ...J I 100 I 050 I OOO+-----~------~----_r------r_----_.----_.------,_----~ 000 10 00 20 00 30 00 40 00 50 00 60 00 70 00 80 00 I RAINFALL (MM) :1 RAINFALL VS FAECAL COLIFORM I I Figure 22 I I I 500 II (1) 450 :1 ® (1) 400 :1, ,I ® 350 I 0 I 300 ...J ::E I 0 2-60 0 "- 0 I- Z I ::) 8 200 I 0 0 g0 I I !l0 ® I I 00 I I 050 I 000 I TIME MONTHS I FAECAL COLIFORM SEASONAL TRENDS I Figure 23 ------, ~______.. ~~~~3~'~~ P ... Times shown ore Major Flow path prototype hClJrs .." .s. EBB FLOW TIDAL EXCURSIONS c •N (II ------ Times shown ore prototype hours Mojor Flow path ~ FLOOD FLOW TIDAL EXCURSIONS c:.., • I\) CJ) ------ ~ o TIDAL RESIDUALS "'T1 .00 - Net excursion over tidal cycles c ~ I\)...., I I I I I 100 I 90 8 0 I 7 0 ... 6 0 . I % "iii •.. 50 CD I ..II< Z ;;: 4 0 z... .. 3 () I II< ..... I 2 0 I - I o 00001 o OCI 001 vi 10 GRAIN SllE IN MILLIMETERS I CLAY ~~ ___ r~S~I~L~T__ -. ______+- ______r-~S~A~N~D~ ______i__ Fine Mediom 1 I I BED SEDIMENT GRADING CURVE I Bed flOes 10 Chipping Norton Lo ke I I I I Figure 28 ------ o t Bed shear 't : funcloon (0, X) see reference 20 Flume ~ 253mm ~ ~iameteri2mm -r::::::.s-V e loci!y b' Rrof,le Sediment --C Ipmm False fl007 X 105 mm Nat to sea Ie LABORATORY SET UP FOR SHEAR TESTS :n .0 c:... ~ N I QI "'" .-~ "'"- en - 0 <{ .0 _0 w I W u.. a:: <{ I I en L&Jz LL I o L&J I III I I I Figure 30 I I I I Zl I ~ I 9 ~ ...J FiQure 31 '11 I A UfO • I. ___O"'_~ " I I I I I I I I 10 09 I 'i\. 08 ~ I I' j07 "- ~ I i 06 " "- "-i' cl ~ l- ~ 05 ~ tI I ~ ...... ffi "'- ~ " 81 ... ~ Ito" • 0.0 ,"" '"~ ~ ...... ~0-4 " . "'<: I /) Z5 ~ ~ O$tI(j btl ~ '" z ~ ~h_ :!03 ~. ~ ~ ....c ...... I 2 ~ ~ i'---- ...... 02 ------r- I - --- - 01 -- I 5 I 6 I 7 I 8 1-9 110 I 12 I 15 I 20 1-30 I 40 I 50 160 170 I 80 I~ 1100 I SLOPE OF BEACH FACE I I SAND DIAMETER/SLOPE RELATIONSHIP OF BEACHES (from reference 22 ) I I I I I Figure 33 I I I I I I I I I I ;o 01.. > c:) c:: 0 I ~ -~ c:: -Q) E I "0 Q) ." -0 I .~ u =t;- ~ I ...Q. .e E I S'c . "0 ." :3:! I .!! ~ I (/) I • N ... I 0 0 g "0 0 " " 0 0 ~ " FiQure 34 I ~I;...... I Back of beach I RLlOl66 LWN9976 I I 3 I~ I 173 I BEACH ON NORTHERN BANK,NEAR GEORGES RIVER ROAD I I RL 10166 I I I I I BEACH NEAR CHARLTON AVENUE I I Back of beach RL 101 66 I MHWS 10082 I Toe of beach RL 96 4 I~~~~~------I 3 I I BEACH ON WILDLI FE ISLAND RECOMMENDED BEACH PROFILES Figure35A I I I I I I BEACH AT CHIPPING NORTON BAY I I Bock of beach RL 101 66 -';;;"'---'I'III'!RI~f __ I I I Lake bed I RL92 approx I BEACH AT GEORGES HALL BAY I I RLlOl66 I I I I I BEACH NEAR HOLLYWOOD- DRIVE RECOMMENDED BEACH PROFILES Figure 35 B I I WoterSZ level ____ _ I ..... I I I I I I I I I _ A t---___-=--u ____-+--_-=-u _~ I Meon ve1CX:lty DevKJtlon from mean I I DEPTHWISE VARIATION OF VELOCITY I I I' I I Figwe 36 ----~ ------, , No Flow Mainstream flow Area be\wteen moveable '- ,oundarles ~odebay "\ I ~'Irculohon , "\ ~\ ExpansIon Mainstream flow between solid boundaries ,--- FLOW PATTERNS ::!J 10 C Ci ------CIoI ~ I I I Set pulse length I Frome rate Slow Approx Shutt r jl2V Power running I second ., I Osallatar pulse Solenoid Suppl,y I I BOLEX SINGLE FRAME TIMER I I I I I I Set open time 5 - 20 sec I +12V Variable I second Power ~ 240V pulse ~ I pulse - Supply .. ~ generator I Tngger'---""'" Shutter Motor I SolellOld Wmder I PENTAX SHUTTER TIMER I ELECTRONIC DETAI LS FOR PHOTOGRAPHICS I Figure 38 I I I I I uniform flow I z I I I f~U I DETAIL I I I I , I I / ---- .:-.:::.:=:.===... , " Zl = e Zo I Bed level I t------(UZ' )max t------Uo------~ I I COMPARISON BETWEEN VELOCITY PROFILES FOR WAVES a CURRENTS (From Ref 34) I Figure 39 I I) I (Uz.} max I I I ( Uz') max sin wt I I I I Current direction I I I I (Components at Elevation Z' above bed) I I I I Direction I prop~~tlon~wave VELOCITY COMJONENTS FOR COMBINED CURRENT AND WAVE ACTION I ( From Ref 34) I Figure 40 I I I I I I I I I I PLATE I. EBB TlDE - TIDAL SIMULATION I I I I I I I I I PLATE 2. EBB TIDE _II START-UP' TEST I I I I I I I I I I I PLATE 3. FLOOD TIDE - TIDAL SIMULATION I I .1 I I I I I I I I --- -- PLATE 4. FLOOD TIDE- "START UP" TEST I I I I I I I I I I I PLATE 5. LOW WATER LEVEL I I I I I I I I I PLATE 6. HIGH WATER LEVEL I I I I I I I I I I I PLATE 7. FLOW 45 m3 /s (PROTOTYPE) I I r· I I I I I I I PLATE 8. FLOW 90 m3 /s (PROTOTYPE) I I I I I I I I I I I PLATE 9. UNROUGHENED BED I I I I I I I I I I PLATE 10. ROUGHENED BED I I I I I I I I I I PLATE II. EBB TIDE - WITH PROSPECT CREEK I I I I I I I I I I PLATE 12. EBB TIDE-WITHOUT PROSPECT CREEK I I I I I I I I I I .." - r I PLATE 13. FLOOD TIDE-WITH PROSPECT CREEK I I I I I I I I I I PLATE 14. FLOOD TIDE-WITHOUT PROSPECT CREEK I I I I I I I I I I I PLATE 15. CONFIGURATION 6 - FLOOD TIDE I I I I I I I I I PLATE 16. CONFIGURATION 6- EBB TIDE I I , ~I I ! I I I I I I I PLATE 17. CONFIGURATION 6 - FLOOD TIDE I (Prospect Creek end of model) I I I I I I I I PLATE 18 CONFIGURATION 6- EBB TIDE I ( Prospect Creek end of model) ) I Ohr. 10 min. I hr. 10 min. ,I I I I I .. ~ I 2 hr: 20 min. 3hr OOmin. I I I I I 4hr. 40min. 6 hr. 00 min. I ( Prototype times are approximate only) I DYE TRACING FLOOD TIDE SEQUEN.CE Plate 19 I I I I I Ohr. 10min I hr. 10 min. - I I I, 4 I t I I I hr 50 min. 2 hr 10min. " ~ . I , I I I I 2hr. 20min. 4hr.IOmin. I (Prototype times are approximate only) DYE TRACING EBB TIDE SEQUENCE Plote 20