The NSW Government’s Metropolitan Water Plan 2006 included the action to investigate options for increased transfers of water from Tallowa Dam to Sydney, and the development of a new environmental flow regime for the Shoalhaven River downstream of Tallowa Dam. A calibrated numerical model was required to systematically quantify the changes to estuarine saline conditions associated with reduced fresh water inflows. WRL was commissioned by the NSW Department of Natural Resources (DNR).

One dimensional hydrodynamic and salt dispersion RMA models were established. Excellent model calibration was achieved against recorded water level, discharge and salinity data. This required a well defined model mesh and careful consideration of internal and external parameters. A decade of salinity records was available for model verification. Modelling was undertaken for many different freshwater inflow scenarios, each of 96 years duration. To quantify the changes in saline dynamics between two scenarios, it is necessary to compare the statistics of the saline structure of long duration numerical model simulations. Differences in saline dynamics were assessed based on the probability of exceedence of salinity thresholds at various river locations (chainages), chainage statistics for various salt thresholds, and the duration of salt intrusion events at selected chainages. Changes in this structure provided a quantitative basis for understanding the effects of altering freshwater inflows.

The results of salinity modelling can be assessed in terms of a comparison of how salinity varies at a particular location, or how chainage (and habitat availability) varies for a particular salinity threshold. To quantify the changes in saline dynamics between scenarios, an assessment can be made of the:

• salinity statistics at various sites (chainages);
• chainage statistics for various salinities;
• variability in salinity along the estuary; and
• duration of saline intrusion events.

The model finding allowed the NSW Government to determine a set of pumping rules (duration, volume and cease to pump limit) which minimised the adverse impacts of extreme saline intrusion during dry periods.

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Mike began his PhD at WRL in October 2009. The title of his project is Forecasting 3D Wave Breaking in Directional Seas. He will seek to numerically and experimentally investigate whether a threshold for energy convergence rate, as proposed in a recent study on 2D wave groups, is suitable for predicting wave breaking onset and breaking strength. Experiments will constitute generating waves in the large wave basin, recording various parameters, followed by interpolation and computational analysis.

Mike completed his degree in Civil Engineering at the University of Canterbury in New Zealand, majoring in Fluid Mechanics and Geotechnical Engineering. Since graduating in 2007 Mike has been working for a commercial consultancy in Christchurch, NZ, as a geotechnical engineer undertaking project management, site investigations and technical reporting. He brings to WRL hands on professional experience and a practical problem solving nature.

A typical image from the Collaroy-Narrabeen coastal monitoring cameras

The same location on the morning of 23 September 2009, when a dust storm arrived in Sydney

(Back) Tom Shand, Melissa Mole, Ron Cox, Chris Blenkinsopp, Ian Turner, Jamie Ruprecht, Brad Morris, Will Glamore
(Front) Alessio Mariani, Duncan Rayner, Matt Blacka, Mitch Harley, Ian Coghlan
(Absent from photo are Bill Peirson and James Carley)

List of Papers

Blacka, M., Carley, J., Corbett, B. and Jackson, A. (2009) Wave Transmission over Low Crested Geotextile Breakwater Structures

Blenkinsopp, C.E., Turner, I.L., Masselink, G. and Russell, P.E. (2009) Measurements of Net Cross-Shore Sediment Flux at the Timescale of Individual Swashes

Carley, J.T., Blacka, M., Mariani, A., Cox, R.J., Attwater, C. and Watson, P. (2009) Integrated Assessment of Coastal Hazards and Climate Change for Clarence City, Tasmania

Coghlan, I., Carley, J., Cox, R., Blacka, M., Mariani, A., Restall, S., Hornsey, W. and Sheldrick, S. (2009) Two-Dimensional Physical Modelling of Sand Filled Geocontainers for Coastal Protection

Glamore, W. (2009) Restoring Coastal Wetlands: Engineering Nature and Managing Expectations

Glamore, W., Rayner, D. and Miller, B. (2009) Design of an Ebb Tide Release

Harley, M.D., Turner, I.L., Short, A.D. and Ranasinghe, R. (2009) An Empirical Model of Beach Response to Storms - SE Australia

Mariani, A., Blacka, M. and Carley, J. (2009) Extreme Wave Overtopping of a Vertical Breakwater. A Physical Model and Desktop Investigation

Morris, B. and Turner, I. (2009) Intermittently Open-Closed Lagoon Entrance Morphodynamics: Infilling, Stability and Climate Change Impacts

Rayner, D. and Glamore, W. (2009) Understanding the Transport and Buffering Dynamics of Acid Plumes in Estuaries

Shand, T.D., Peirson, W.L., Cox, R.J. and Banner, M.L. (2009) Predicting Hazardous Conditions on Coastal Rock Platforms

Turner, I.L., Masselink, G. and Williams, J.J. (2009) Proto-type Scale Laboratory Study of Groundwater Manipulation within a Gravel Barrier

Webb, T. and Glamore, W. (2009) Sediment Fallout from Dense Outfall Plumes

Client: Hunter Water Corporation
Year: 1996, 1998, 2007, 2008, 2009
Project Reference: 06101
WRL Technical Reports: Burwood Beach Ocean Outfall Monitoring (A96/06); Burwood Beach Ocean Outfall: Testing of 8 Inch Check Valve (A96/18); Burwood Beach Ocean Outfall Monitoring (A96/28); Burwood Beach Ocean Outfall Monitoring & Modelling May - August 1998 (1998/54); Burwood Beach Ocean Outfall Monitoring and Modelling (2007/11); Hydraulic Assessment of Burwood Beach Ocean Outfalls with New Tideflex Valves (2008/02); Burwood Beach Ocean Outfall Modelling 2009 (2009/06); Burwood Beach Ocean Outfall Modelling 2009 Environmental Conditions Preceding Events (2009/19)

3D numerical mesh (RMA-10) designed and calibrated to simulate currents near Burwood Beach Ocean Outfall

Burwood Beach Wastewater Treatment Works (WwTW) is located approximately 7 km south-west of the entrance to the Hunter River at Newcastle, and services approximately 70 km² of the city of Newcastle. Liquid effluent and sludge are disposed of following secondary treatment via an outfall tunnel extending 1500 m offshore of Burwood Beach and discharging into water of 22 m depth. Liquid effluent is discharged though 9 diffuser heads with a total of 71 ports. Sludge is disposed through a separate pipeline (approximately 100 m in length, with 18 active ports) extending from a tenth diffuser head.

Initial work was undertaken in 1996, comprising two field exercises, near-field dilution modelling, and the establishment of a steady state three-dimensional (3D) hydrodynamic and far-field water quality model. WRL was commissioned in 1998 to undertake further monitoring works to investigate the performance of diffusers and subsequent water quality impacts at the Burwood Beach Ocean Outfall under winter conditions.

In 2007, WRL undertook a similar study to determine the performance of the outfall under stratified summer condition for present (2007) and future (2030) flow rates. This was achieved through the use of dye isotope (Rhodamine WT) tracking in the field coupled with extensive deterministic modelling of the likely plume dynamics to generate concentration statistics.

In 2008, WRL in conjunction with the Water Research Centre (WRC), of the University of New South Wales was commissioned by the Hunter Water Corporation (HWC) to undertake additional data analysis and modelling tasks related to the Burwood Beach Ocean Outfall. The outcomes of this study are to be utilised by the WRC to assess infection risk probabilities associated with the full range of hazardous event likelihoods at eight ‘representative’ sites along the Newcastle coast.

Further work was undertaken in 2009 with the water quality capabilities of the far-field random walk model (3DRWalk) upgraded to include: a range of diurnal solar radiation variables to be applied and linked to particle depth; and, a series of output variables to be generated for each particle and time step. For this study, the winter 1998 and the summer 2007 datasets were proposed to represent onsite general winter and summer conditions. To determine if the existing data represent long term trends, the data was compared to long-term datasets from other representative sites. This analysis was undertaken via a comparison of both wind and current roses, coupled with spectral analysis, to determine the validity of the 1998 and 2007 data sets. The summer and winter datasets were coupled with the 2007 and 2030 effluent flow rates as inputs to the updated 3DRWALK model to enable particle inactivation to be accurately modelled. Both spatial and temporal statistical data were extracted for assessment of hazardous events.

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Client: Clarence Valley Council (via Department of Commerce)
Year: 2008-Ongoing
Project Reference: 08069
WRL Technical Report: Detailed Concept Design of Yamba-Iluka Ebb Tide Release (2008/28)

Clarence Valley Council is currently upgrading the sewage treatment systems for the townships of Iluka and Yamba. These towns are located at the mouth of the Clarence River, with Iluka to the north and Yamba to the south of the river entrance. In 1997, the NSW Coastal Policy stated that “new ocean outfalls will be embargoed until a full investigation of alternative wastewater strategies has been undertaken and considered by the Government”.

Detailed discussions have been undertaken to determine a socially acceptable location for the recycled water releases. These discussions have involved a range of stakeholders including representatives from local recreational fishing groups, local commercial fishing cooperatives, the NSW Maritime Authority, the NSW Department of Lands, the NSW Department of Primary Industries (including NSW Fisheries), the NSW Department of the Environment and Climate Change, local Aboriginal Land Claimants and local community working groups.

Upon acceptance of a potential release location, fieldwork was undertaken to: survey the lower Clarence estuary, determine potential effluent flow paths and measure ebb tide discharges and velocities. This was used to develop a hydrodynamic model that was calibrated and verified for the lower Clarence River. The model was shown to adequately describe the hydrodynamics in the vicinity of the proposed ebb tide release and is fit for the intended purpose of providing base data and analysis for the release designs. A range of model simulations were tested to optimise the design of the ebb tide release. Exit velocity and head loss calculations were used to develop optimal configurations for Yamba and Iluka. Water quality modelling in the near-field zone was then employed to calculate the dilutions that would be achieved with these diffuser configurations under different ambient flow regimes.

A subsequent post-flood survey by WRL in May 2009 has increased the hydrosurvey dataset for the lower Clarence River, providing increased confidence in determining the design of the ebb tide release. Work on this study is presently ongoing.

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(L-r) Gabriel Rau, Anna Greve, Dr Wendy Timms, Dr Martin Andersen, Andrew McCallum and Professor Ian Acworth

During the week long congress, Dr Martin Andersen presented a paper linking hyporheic zone water chemistry and stream bed ecology to groundwater discharge and recharge in Maules Creek, Australia.  Another paper on hydraulic investigations of surface and groundwater interactions in a sub-catchment of the Namoi River was given by Andrew McCallum. The latest research on using natural heat as a tracer to quantify surface and groundwater connectivity in the Namoi catchment was presented by Gabriel Rau. Anna Greve gave a presentation on the use of electrical resistivity tomography to detect crack depth and preferential flow in irrigated clay soils. Finally, Dr Wendy Timms spoke on groundwater and salt fluxes in a weathered and fractured granite terrain in the Macquarie catchment of NSW, Australia.  Several similarities and differences in groundwater fluxes in the weathered granite around Hyderabad and the Baldry catchment were noted.

After the conference, the WRL team enjoyed several days exploring incredible India and very much enjoyed the fascinating history and excellent flavour of the local food.

Dr Martin Andersen (right), with his poster ‘Linking Hyporheic Zone Water Chemistry and Streambed Ecology to Groundwater Discharge and Recharge, Maules Creek, NSW, Australia’

Gabriel Rau, Anna Greve and Dr Martin Andersen

Dr William Glamore of the WRL Project team presented a paper titled Ecological Restoration of Coastal Wetlands: Global Lessons Implemented Locally.

The presentation discussed the lessons gained from William’s Churchill Fellowship (International Coastal Wetland Restoration Practices), which involved a 3 month tour of 26 coastal wetland restoration sites around the world (USA, The Netherlands, Vietnam, Indonesia and New Zealand) and how these lessons have been applied at a range of coastal wetland restoration sites in Australia. The recent on-ground work at the Tomago wetlands, near Newcastle, was highlighted. Major lessons gained from the on-ground experiences were discussed and highlighted. The presentation finished with a discussion on major areas of current research and project work.

For more information, Dr William Glamore can be contacted directly at: w.glamore@wrl.unsw.edu.au

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After initial construction or following maintenance work ocean outfalls may be filled with seawater that must be purged with less dense effluent. Experience with long riser outfalls has shown that seawater intrusion and purging can pose special problems for this type of outfall. Indeed, if the outfall is not properly purged it may not operate as designed and seawater could be drawn into the risers. The buoyancy of the effluent inside a riser reduces pressures in the tunnel causing seawater contained in unpurged risers to recirculate through the riser section which impacts the outfall performance and reduces effluent dilution. This reduced performance may lead to partial blockage of the outfall due to the build-up of marine growth and sediments.

(Top) Geometry of the Burwood Beach Ocean Outfall
(Bottom) Density in the Malabar Ocean Outfall

Over many years, outfall purging has been successfully studied at the Water Research Laboratory through physical modelling and hydraulic assessments using in-house Fortran programs developed at WRL. Recent advances in computer power and Computational Fluid Dynamics (CFD) provide a useful alternative method for outfall purging assessments and design methods. A 3-Dimensional (3D) numerical model using the CFD software ANSYS-CFX has been developed at WRL to simulate the purging process in two different ocean outfalls to validate the CFD software and verify its accuracy and sensitivity for future outfall assessment. As a case study the model has been applied to the deep water Malabar Ocean Outfall in Sydney and the Burwood Beach Ocean Outfall near Newcastle.

Results over three varied flow rates for the Malabar Ocean Outfall showed that the time for purging the riser and the effluent flow rate for when the purging of the riser occurred were in agreement with the experimental values of Wilkinson et al. (1989, 1992) and with the purging condition for long riser outfalls found by Wilkinson et al. (1985).

Results along the tunnel and in the risers of the Burwood Beach Ocean Outfall, applying two types of outlet at the riser boundaries and two depths of effluent - seawater interface, were compared to the hydraulic assessment of Miller et al. (2008) over eight varied flow rates. Mass flow outlet conditions at the riser boundaries, discharge and velocity values along the tunnel and in the risers were very close to the results of the hydraulic assessment, regardless of the initial depth of effluent - seawater interface and the tunnel flow rates being modelled.

(Top) Discharge along the tunnel over varied flow rates in the Burwood Beach Ocean Outfall; (Bottom) Purging of the risers of the Burwood Beach Ocean Outfall

By applying pressure outlet conditions at the riser boundaries, numerical results varied according to the tunnel flow rates and the initial depth of effluent - seawater interface modelled. For a ‘no interface’ initial condition, the flow rates did not influence the numerical modelling as the discharge and velocity values along the tunnel and in the risers matched very well the results of the hydraulic assessment. But for an ‘effluent - seawater’ interface initial condition the flow rates seemed to have a greater influence on the hydraulics of the outfall, as a characteristic flow rate of 2 m³/s was shown to affect the numerical modelling, which was also the flow rate to start purging at least one riser of the Burwood Beach Ocean Outfall. Single phase modelling was not sensitive to the boundary type conditions and flow rates and showed very good hydraulics results in agreement with the hydraulic assessment. However multi-phase modelling was clearly sensitive to the boundary type conditions and flow rates.

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Client: BlueScope Steel Pty Ltd
Year: 2008-2009
Project Reference: 08035
WRL Technical Report: Physical Modelling of BlueScope Steel’s Steelworks Cogeneration Plant Saltwater Cooling System, Port Kembla (2009/01)

(Clockwise from top) Flow pattern in the tundish for 100% design flow/high tide/no fouling; Flow pattern in the outlet for 100% design flow/high tide/no fouling; Flow pattern in the outlet pipe for 100% design flow/high tide/no fouling; Flow pattern in the air release structure for 100% design flow/high tide/no fouling.

The Water Research Laboratory (WRL) has undertaken physical modelling of a proposed section of the saltwater cooling system at the Port Kembla Steelworks Cogeneration Plant. BlueScope Steel’s Steelworks Cogeneration Plant will use saltwater for turbine condenser cooling. The flow will come from condensers and enter a tundish, where it will flow over a weir and through dual outlet concrete pipes. Further downstream, about 800 m from the tundish, the pipes combine into a discharge structure where the flow enters the harbour with tides affecting the outlet conditions. It has been identified that at some flows, tidal levels, and fouling conditions, air entrainment is a distinct possibility which has potential for serious negative impacts on system operation.

The model investigated flow through inlet pipes into the tundish and out through discharge pipes for varying flows, ocean tide levels and fouling conditions. The first phase of testing concentrated on flow patterns, air entrainment motion and the quantity of air released within the tundish, discharge pipes and air release structures. This testing allowed for evaluation of the initial design and showed opportunities for improved flow conditions in modifying the model design: changing the height and shape of the weir within the tundish, and installing bellmouths in the outlet pipes. Modifications of the model design were undertaken for a second phase of testing and showed generally improved conditions in terms of air entrainment and flow patterns. They generated reduced turbulence and aeration within the tundish and less air suction into the outlet pipes as well as better performance of the air release structures.

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