WID involves injecting water into the sea, or riverbed sediment, to fluidize the sediment and create a density current which flows due to gravity. This means the seabed must slope away from the dredge area for the approach to be successful.

The process of using Tiamat also injects water in the bed sediment to dilute and help mobilise it, but Tiamat has a suction pump which extracts the diluted bed sediment up a pipe where it is released into the mid water column where it is transported away by tidal currents.

Both dredging approaches use a suction pump to pump the sediment up from the bed. For side casting, the sediment is pumped to the surface and is then discharged through an elevated discharge boom over the side of the dredge vessel, with the sediment discharged into the air before it reaches the water surface.

Tiamat only pumps the sediment into the mid water column where it is discharged, meaning the sediment is not pumped above the water surface, and it is not exposed to the air.

Both dredgers pump sediment from the seabed using a suction pump. For the TSHD, this sediment is pumped onto the vessel where it is stored in a large hopper. Once the hopper is full, the TSHD sails to a designated offshore disposal site and the hopper doors are opened to place the sediment. This often means that a considerable amount of time and energy is used for the placement of the sediment.

Tiamat only pumps the sediment into the mid water column where it is discharged. This means that the dredger can dredge continuously without needing to sail to an offshore placement site. It also means sediment is released into the estuarine

Tiamat has some visual similarities with a bed levelling bar and both can be operated by similar vessels. However, a bed levelling bar does not have any pumps and so is only able to redistribute bed sediment, this means only high spots can be removed or sediment from high sedimentation areas can be moved away from the site.

Tiamat includes pumps to help dilute and mobilise the bed sediment and to pump it into the mid water column, meaning it can remove sediment from the bed rather than just redistributing it like a bed leveller.

Monitoring during Tiamat operation has shown a high suspended sediment concentration (SSC) plume occurs immediately behind the Tiamat, however this quickly disperses and does not impact the wider area.

The pump rate can be reduced, or a smaller Tiamat can be built to limit the SSC for areas where a localised plume could pose a risk to sensitive receptors.

Monitoring undertaken at the Port of Felixstowe has estimated that using Tiamat has a daily production rate of 23,500 m3/day (in-situ volume). This is comparable to the daily production rate of a small to medium TSHD (hopper size of around 4,500 m3). These production rates are based on Tiamat operating continuously for 12 hours per day, while the TSHD operates for 24 hours per day with dredging occurring for 35% of the time, combined with sailing to and from the disposal site occurring for 65% of the time.

It depends on the dredging problem that needs to be solved. To disperse sediment, the ideal location to be dredged would be predominantly silt and clay and for there to be relatively strong tidal currents to ensure the suspended sediment is transported away from the dredged areas.

However, where the issue is the navigability of the sediment, then tidal range is less important as Tiamat is excellent in reducing the sheer strength of silt and mud.

Due to the ability to adapt the size and power of Tiamat, it can also be used in locations where conventional dredging methods are either too expensive or inaccessible, such as reservoirs, canals, and small waterway. Here the Tiamat can help keep the sediment in suspension for longer periods, and deposited in the estuarine system if required.

Each location would have to be assessed to determine the best way Tiamat can add value to the dredging strategy and protocol.

Tiamat is not sold as a device, but we are happy to discuss your dredging needs and create a suitable commercial offering.

The cost savings achieved over time vary from location to location depending on existing dredging methods being used, volume of sediment, location of disposal site, hydrographic conditions and the dredging and environmental problem that needs to be solved.

However, the cost of dredging with Tiamat is reduced up to 50% compared to TSHD.

Yes. The financial case will vary from location to location depending on existing dredging methods being used, volume of sediment, location of disposal site, hydrographic conditions and the dredging and environmental problem that needs to be solved.

We have produced a white paper on Tiamat’s use in the Harwich Haven. This is available here.

In addition, HR Wallingford has also produced a paper on the success of Tiamat in the Harwich Haven that was presented at WODCON 2022 in Copenhagen.

In Harwich, we expect to reduce our GHG emissions by between 65-95% depending on fuel type and reduce maintenance dredging costs by up to 50% from using Tiamat as part of the Harwich Haven Authority’s dredging strategy.

A port or river authority will need to liaise with its environmental regulators to ensure using Tiamat is suitable dredging technology.

Tiamat was developed by the Harwich Haven Authority, which is in an area that is subjected to the highest UK environmental and ecological standards. By working with the respective UK environmental regulators, HR Wallingford and Royal Haskoning, it obtained consent for using Tiamat.

Each location, jurisdiction and country will have its own regulations and legislation regarding dredging. Tiamat was trialled in the UK, in a location subjected to the highest UK environmental and ecological standards. By working with the respective UK environmental regulators, it obtained consent for using Tiamat.

The current Tiamat has a beam of eight metres and weighs 18 tonnes, and can be deployed on a workboat or multi-cat that is 27m long and has an A frame and crane. A Tiamat of this size will have a productivity of about 23.5K m3 per 12-hour day.

Tiamat can be made larger or smaller and length of its sediment flume adjusted and made to suit the location being dredged. A larger Tiamat may require a larger marine craft, whilst a smaller Tiamat could be deployed on a smaller marine craft.

The Authority wanted to resolve three maintenance dredging problems. These were:

● How to reduce the emissions relating to its dredging activities?
● How to dredge in a more environmental manner?
● How to reduce the cost of maintenance dredging?

Tiamat was invented by the Authority’s Harbour Engineer.

The Authority trialled the use of Tiamat from 2019 to 2021; part of this time was spent on product development. Since 2021, the Authority has been using Tiamat as part of its dredging strategy alongside TSHD and the use of some small WIDs.

Yes. The use of Tiamat can be impacted by bad weather; the extent of this will be dependent on location and the type of marine craft used.

It is expected that Tiamat will be used to complement the use of TSHD, and as result some disposal will still take place.

Each jurisdiction will have their own rules relating to the disposal of the sediment. The location and rules relating to disposal of dredged material are designated by the respective marine authority. Normally licences must be obtained to dispose of dredged material, but not the non-disposal. Nevertheless, the use of Tiamat should be considered alongside discussions with the relevant environmental bodies.