The hopper dredger Pedro Alvarez on the Elbe
Under water

All harbours must dredge

Whether it’s Bremen, Antwerp, Rotterdam or Hamburg – all ports have one thing in common: to ensure that ships can enter and leave unhindered, excess sediment must be dredged and relocated on an ongoing basis. But how do other ports go about it? What is the same, and what is different?

Section of a map of Europe showing the UK, Netherlands, Belgium and Germany with circles symbolising relocation sites and dredging volumes and a pie chart showing dredging volumes in European countries.
Relocation sites for dredged material in the North Range. The larger the circle, the higher the relocated quantity. Data source: OSPAR

More than 100 million tonnes of sediment are dredged and relocated in Europe every year. And because all ports have to dredge, we have been in close contact with experts from other ports for years. We work together on many projects. Although we are also in competition, there are many common challenges. We can learn a lot from each other, especially when it comes to removing excess sediment from harbour basins and waterways.</p

<p>One thing we have in common is that the sediments must be analysed for pollutants before dredging. The EU sets requirements for this, which are implemented by the federal states. The following applies to all of them: low-contaminated sediments may and should remain in the water, while higher-contaminated sediments must also be brought ashore in other harbours.

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<p>What happens to contaminated sediments varies, however. Hamburg and Antwerp treat them in special facilities. There, the contaminated fine-grained mud is separated from the clean sand and dewatered. The METHA in Hamburg was the model for the AMORAS treatment plant in Antwerp. In Bremen and also in Hamburg, the sediments are dewatered in special fields. The dredged material is then deposited or utilised, for example in dyke construction or as sealing material. In Rotterdam, contaminated sediments are disposed of untreated in the Slufter, a huge underwater landfill on the edge of the North Sea.

Interior view of the AMORAS industrial dredged material treatment plant in Antwerp
AMORAS filter presses - contaminated mud is also treated in a large-scale plant in Antwerp. It was modelled on the METHA in Hamburg.
The Slufter dredging site in Rotterdam with mud and tideways, a landfill site and wind turbines
What looks like mudflats is actually highly contaminated harbour silt in a huge underwater landfill on the edge of the port of Rotterdam, the so-called "Slufter".
The hopper dredger Pedro Alvares on the Elbe
In most harbours, the large hopper dredgers perform the main work in maintaining the water depths.
A suction dredger in the harbour of Emden
Ships also travel through thin layers of silt in the Ems. In an area of the harbour that is closed off from the tides, the mud is even artificially kept in suspension with suction dredgers instead of being removed.

Another common feature is that the right dredger must always be used. In order to be able to react flexibly to the respective requirements, the equipment, especially the large hopper dredgers, is hired from specialised dredging companies. At most, smaller dredgers such as grab dredgers, dredgers on pontoons, dredgers or silt harrows are operated by the harbours themselves, which is also the most economical way.

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<p>Sounding vessels, which are often in permanent use, are maintained by many harbours themselves. This is another thing they have in common: soundings must be taken before dredging. This determines where the depths are sufficient and where excess sediment needs to be removed. We also work together with other ports on this, for example in the "nautical depth" project with Rotterdam and Antwerp, which aims to determine exactly when a layer of silt needs to be dredged or when it is so thin that it can still be safely navigated through - like thick cocoa.

Once the sediments have been tested, and if they are only slightly contaminated, they are usually picked up with large hopper dredgers and returned to the water at other locations, which is standard international practice. Rotterdam uses a large area in the North Sea, just under 10 kilometres off the coast, for this purpose. Around 5 million tonnes are relocated here every year. The pollution of the sediments is very similar to the dredged material that we bring to the E3 tonne in the North Sea. Rotterdam sees the relocation as a sustainable improvement, as sediments are also urgently needed off the Dutch coast to protect against rising sea levels. Antwerp also uses dredged material as a resource. It is used to "feed" sandbanks in the Scheldt, which has a favourable effect on the currents.</p

<p>Decades of dialogue with other ports have made it clear to us that Hamburg takes sediment management particularly seriously and is constantly looking for improved solutions. We set global standards when it comes to testing sediment qualities, investigating suitable relocation sites, handling contaminated dredged material and continuously monitoring the potential impact of our dredged material shipments. We are particularly transparent: our sediment analyses are published on our website at short notice, as are the scientific monitoring reports, impact assessments and the annual reports on our water depth maintenance. And if any information is missing, we are here to answer your questions, e.g. via tideblog@hpa.hamburg.de.

A film by the SAT1 Regional editorial team also shows how sampling and dredging works in the harbour.

FAQ on dredging in the ports of Europe

FAQ on dredging in the ports of Europe

 

Whether Bremen, Antwerp, Rotterdam or Hamburg, the currents of the sea and rivers ensure that new sediments are constantly being deposited. This is why all European ports must regularly remove sediment from harbour basins and waterways. This is the only way ships can arrive and depart safely. In total, over 100 million tonnes of sediment are dredged and relocated in Europe's container ports every year.

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Ports in Europe face the same challenges due to strict EU-wide regulations: Sediments must be tested for pollutants in advance. Sediments with low levels of contamination may remain in the water, while more highly contaminated material must be treated on land or deposited. Sufficient suitable relocation sites must always be provided for this purpose.

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The harbours handle contaminated material differently:

  • Hamburg & Antwerp: Treatment in special facilities where mud and sand are separated and dewatered (e.g. METHA in Hamburg, AMORAS in Antwerp).
  • Bremen & Hamburg: Dewatering on special fields and subsequent landfilling or recycling, for example in dyke construction.
  • Rotterdam: Depositing the contaminated sediments in a large underwater landfill in the North Sea (the "Slufter").

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Yes. Despite the competition among themselves, many European ports regularly exchange information and work together on projects to learn from each other.

 

 

Depending on the requirements,different dredgers are used. Large hopper dredgers, which are hired from specialised dredging companies, carry out most of the work involved in maintaining water depths. Smaller dredgers are sometimes operated by the harbours themselves.

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