Virtual visualisation of the Thames

Virtual reality is being used to visualise the tidal hydraulics of the Thames Estuary and as a future prediction tool explains Maggie Templeman of Superscape.

The Environment Agency (EA) is in the early stages of using a PC-based virtual reality model to demonstrate visually the tidal hydraulics of the Thames estuary and to show the impact of flash floods, sewage discharges and other forms of pollution. The virtual reality model depicts the whole estuary which extends approximately one hundred kilometres from Teddington Lock in West London to Shoebury, east of Southend. The tidal river varies in width from less than 100m in the upper reaches to some 7km at Southend. The model has been developed by Virtual Worlds using Superscape¹s PC-based authoring software, VRT5.

Over the years, we have been trying to find a way of presenting the information in as easy to understand a manner as possible. There are so many factors involved in the Tideway that it is clearly a most complex and complicated issue. We have used 2D graphs but these can be quite difficult to understand for those not intimately involved in the estuary. We have also developed a number of 3D perspex models, which seek to visualise a particular pollution event. Although these have been well received, they can only be used to show one single event, they are static and, of course, they can only be used for historical data, not as a prediction tool. People kept saying to us Œif only they moved, it would be so much easier to understand." "Our motivation for using virtual reality was that it had the potential to provide us with one single package which could take data from all the different systems, including the automatic monitoring stations and linking it to tidal data present the information as an extremely visual, interactive 3D model ­ and that as the next stage, we could go on to use it as a innovative predictive tool."

EA protection staff obtain water quality information from eight automatic monitoring stations sites between Kew and Purfleet. These stations collect data (using an automated telemetry system) on dissolved oxygen, temperature and conductivity. Manual sampling is also undertaken using a survey launch. About twenty sites along the tideway are sampled weekly in the summer and fortnightly in the winter, while some key sites are sampled monthly for heavy metals, organic pollutants and other persistent chemicals. The Tideway is home to some of Europe's largest sewage treatment works (at Mogden, Beckton and Crossness).

The EA monitors the quality of the Thames Tideway by dividing the water into a number of discrete segments called zones which move back and forth with the tide.

The virtual reality model of the Thames Tideway has been designed by one of Superscape¹s authorised developers Virtual Worlds, headed by Dave Walters. ³The initial version of the virtual reality model visualises the entire 100 km stretch of the Thames Tideway, and includes models of the various monitoring stations, pumping stations, sewage treatment work outfalls, and recognisable landmarks such as the Houses of Parliament, Tower Bridge, Millennium Dome, Kew Pagoda, Southend Pier, the Thames Barrier and all the bridges along the river. Using the existing Œzonal' approach to monitoring water quality, the system allows the user to introduce pollution (shown in red) into a specific zone and monitor its progress downstream. The Thames Bubbler can also be deployed in the system and the effect of introducing oxygen can also be seen.

Unlike the Œreal world, the model also includes an underwater visualisation of the Tideway, which is shown in an Œanimated format. Oxygen levels are shown underwater, and the different species of fish in each section of the Tideway are depicted. The model was also required to visualise the effect of polluting discharges into the Tideway, primarily from pumping stations (located at Chelsea Harbour, Hammersmith Bridge, Chelsea Bridge and Abbey Mills), as well as from the sewage treatment works at Isleworth, Kew, Crossness and Beckton. It was important for the model to be able to cope with discharges entering the Tideway at any state of the tide, into any zone and for any period of time.

Although it is still early days for the EA and its new virtual reality model, the first benefits are already apparent. The user can identify a particular stretch of the river, cause an imaginary pollution incident and then watch events unfold. No other technology can do this. As the pollution plume travels either down or up the river, it passes an automatic monitoring station which alerts the Thames Bubbler. This in turn rushes to the location of the plume and begins to inject oxygen to replace that taken up by bacterial. Diving underwater in the model reveals the highly textured fish reacting to their changing environment.

Simulation time (the time between movements of the tide and/or the zone) can be varied so that the extent of travel of the pollution plume can be seen at different speeds. Immediately the viewer is made aware of the tidal flow within this estuary and that whatever is thrown into the Thames will travel backwards and forwards for a long, long time. A phenomenon that can really only be appreciated by the lay person when they see the situation visualised in virtual reality.


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