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• Hydrodynamic Studies
• Discharge and OilSpill Modelling
• Wave Studies
• Storm Surge, Tide and Coastal Flood Modelling
• Tide and River Flood Modelling in Coastal River Systems
• Atmospheric Circulation
• Atmospheric Pollution Studies
• Dredging Simulations

Hydrodynamic Studies

For studies of hydrodynamic circulation and sea level variation under ambient and extreme weather conditions, GEMS have developed the GEMS Coastal Ocean Model:GCOM3D. GCOM3D is an advanced, fully three-dimensional, ocean-circulation model that determines horizontal and vertical hydrodynamic circulation due to wind stress, atmospheric pressure gradients, astronomical tides, quadratic bottom friction and ocean thermal structure. The system will run on Windows/NT or UNIX platforms. GCOM3D is a fully functional anywhere in the world using tidal constituent and bathymetric data derived from global, regional and local databases. The model scale is freely adjustable, and nesting to any number of levels is supported in order to suit the hydrodynamic complexity of a study area. As the model is fully three-dimensional, output can include current data at any or all levels in the water column. A 2 dimensional version of the model that includes tidal and flood inundation is also available for use in river systems. The model can be used for simulations of hydrodynamic circulation under seasonal, real time, or extreme weather conditions.

Example applications include:

• Forecasting, now-casting or hindcasting ambient and extreme water currents and sea levels (eg. for advice to maritime operations or for return-period calculations);

• Determining affects of proposed river or coastal modifications;

• Determining affects of seasonal wind conditions on circulation;

• Specification of ambient and extreme currents for the design of surface and undersea facilities;

• Development of criteria for the design of undersea pipelines for stability and fatigue analysis;

• As input to modelling the fate of spills, leaks, discharges and other anthropogenic activities (see below).

Discharge and Spill Modelling

GEMS have the expertise in modelling the transport, settlement and resuspension of conservative particles, such as sediment or other inert material. 

GEMS uses its three dimensional ocean model, GCOM3D, and its associated 3D plume model PLUMETRAK to assess the fates of the discharge.  GCOM3D has been extensively tested across a wide range of applications on the North West Shelf and throughout the world.  PLUMETRAK is the integrated, high-resolution 3D dispersion model developed by GEMS for modelling a wide variety of discharge materials including sediments, sewerage, thermal discharges, oils and chemical releases. Our oil spill prediction model, OILTRAK3D, is a sub-model of PLUMETRAK.

The model suite quantifies the distribution of each substance spilled or released under controlled conditions.  The model reports mass and concentration levels on the water surface, on shorelines, in the sediments or through the water column as required.  Horizontal and vertical cross-sections are available to better illustrate the three dimensional distributions.  Where multiple chemical constituents are involved, the model can report the distribution of each constituent individually. 

Environmental forcing for GCOM3D includes input of winds, tides and geostrophic currents (subject to applicability).  The wind input may be single station or gridded winds from numerical weather prediction models.  GEMS strongly recommends that close attention be paid to the analysis of environmental forcing, as the results of any plume modelling will not be usable if the model is subjected to incorrect meteorological or oceanographic data.  PLUMETRAK can be used stochastically to simulate a large number of random events over time or can be used for specific case studies.  Again, the selection of the forcing for the case studies needs to be carefully considered.  

3Oilspill Risk Assessment on the North West Shelf of Australia

Example applications include:

• Emergency oil spill trajectory and fate modelling;

• Quantitative risk assessment for oil spills, as contingency planning for environmental risk assessment;

• Modelling the fate of drilling mud, produced formation water, hydrotest water and other discharges from oil and gas facilities;

• Backward trajectory modelling to define source locations of oil-slicks, flotsam and jetsam;

• Modelling the fate of particles contaminated by hyrdrocarbons, pesticides, metals or radionuclides(eg NORMs);

• Defining the most probable, and potential paths of larvae from and to defined locations(eg to define upstream and downstream locatons during defined seasons);

• Defining residence times, flushing, sand scouring or deposition under existing or modified conditions (eg. for investigations of affects of channel dredging, port developments, or river and coastline modifications);

• Modelling the fate and effects on water quality of sewage, process water or other contaminated inputs from point and diffuse sources.

• Investigating affects on water quality from proposed or existing developments;

• Determining sources of water quality pollutants (eg. nutrients, biological oxygen demand, turbidity, enteric bacteria).

Wave Studies

GEMS have the expertise in the setup and the running of the third generation spectral wave model, WAM (Max Planck Institute). This model can be operated at variable resolution so as to capture broad-scale ocean wave energy as well as local shallow-water effects such as wave refraction and shoaling. It can be driven by synoptic scale winds derived from a range of dynamic atmospheric models or by analytical models, such as the GEMS tropical cyclone model.

GEMS have used the wave model in several environmental and design studies around the Australian coast. Wave model output has also been used to determine wave-induced currents over submarine pipeline routes. This has included calculation of along pipeline variation of current forces due to crest length reduction.

GEMS has developed a numerical modelling system to study and predict storm surges and the resulting coastal flooding that could be expected during the passage of severe weather events such as tropical cyclones, cold fronts and other strong wind events. Atmospheric forcing is derived from the GEMS Mesoscale Atmospheric Prediction System (MAPS) or from a tropical cyclone model. The GEMS tides and storm surge inundation model is based on the storm surge model described in Hubbert et al (1990,1991) and in Hubbert and McInnes (1999). GEMS have applied the storm surge system and methodology to a large number of locations around Australia (Port Hedland, Karratha, Cape Lambert, Derby, Onslow, Dampier, Cairns, Gold Coast, Darwin, Mornington Island, Port Phillip Bay). 

Example applications include:

          Example applications include:

For environmental pollution studies in the atmosphere, GEMS apply the output of the MAPS model for dispersion and fate modelling. This work is often carried out in conjunction with Prof. Leslie at the Centre for Environmental Modelling and Prediction (CEMAP) at the University of New South Wales.

Example applications include:

• Simulation of dispersion fields for atmospheric emissions under seasonal conditions;

• Investigation of mitigation efforts to define the most cost-effective options;

• Integrated analysis and modelling for particulates, organic compounds anions and metals in stack emissions.

Once the physical oceanography has been simulated it is possible to study the movement of discharges into the water column  (e.g. sediments, chemicals etc.) or components of the water body itself (flushing rates of harbours, bays etc.).

The GEMS 3D Dredge Simulation Model (DREDGE3D) is used for simulating the specific fate of particles discharged during a dredging program.  This model inputs the physical environmental data from GCOM3D, together with wave data from SWAN and meteorological data, to simulate the movement and deposition, of suspended particles in the water body across the study area.

DREDGE3D was used with great success in the Geraldton Port Redevelopment Project where it was compared with in-situ data, aerial photographs and satellite images. 

In the past 3 years since the dredging of Geraldton Port, DREDGE3D has been used in Mermaid Sound for both the Dampier Port Authority and the Hammersley Iron port expansion projects, Chevron Gorgon dredging at Barrow Island, two projects in Queensland, several developments in the United Arab Emirates and in New Caledonia for the INCO nickel processing plant and port development.

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