The tide and the Elbe pump sediments towards Hamburg

The tides are clearly visible in the tidal Elbe, in the tide-dependent section of river between the weir in Geesthacht and the estuary in the North Sea. The Port of Hamburg also experiences alternating high and low tides twice a day.

But a fascinating movement also occurs beneath the water surface: the forces of ebb and flow operate like a pump in the tidal Elbe. Not only does the more powerful incoming tide push water from the North Sea into the Elbe, but fine, sandy material is also transported upriver. The weaker ebb stream only carries a certain amount of it back out. This phenomenon is known as “tidal pumping”.

The mouth of the Elbe is an estuary

The mouth of the tidal Elbe is an estuary. This kind of river mouth, widened into a funnel shape by the ebb and flow of the tide, only form on coasts with powerful tidal processes and are subject to constant change. The estuary of the tidal Elbe is a highly dynamic transition zone between the river and sea – 200,000 tons of sediment are continually on the move here. Large sections of the estuary are under special protection as habitats. Upriver an inland delta frequently forms, like the highly branched river bifurcation area between Mühlenberger Loch and Geesthacht, in which the Port of Hamburg was constructed.

Links and more (German only)

What does sediment management mean?

As in most harbours in the world, the port basin and fairways in Hamburg must be regularly cleared of sediments. They are continually dredged, otherwise the ships would soon be prevented from entering the port.

Sedimentation means that suspended matter settles on the river bed in low-flow zones. The sediments in the Port of Hamburg consist of fine-grained silt and coarser-grained sand.

The HPA’s task is to ensure the required depths for shipping traffic through sophisticated sediment management and to make sure that the dredged material is handled in a safe and environmentally-friendly manner.

The Forum for Current and Sediment Management in the Tidal Elbe

The jointly developed results (PDF) form the basis for more sustainable handling of sediments. The aim is to ensure that less sediment is produced and that sediment pollution is further decreased. The agreement on the transfer of sediments from Hamburg into the North Sea between the states of Schleswig-Holstein and Hamburg in spring 2016 is a first step. The HPA will work intensively with the region on further measures which could lead to a sustained reduction in dredging volumes. They will be expedited in joint plans under the name “Estuary Partnership”.
Hamburg will also drive forward its commitment to cleaning up the Elbe of pollutants – with the treatment and disposal of polluted sediments ashore and the project ELSA, which is active as far as Czech Republic, in order to support the clean up of remaining pollutant deposits close to the source.

Dredged material from Hamburg in the North Sea

In order to ensure that the Port of Hamburg remains accessible in the summer months as well, the HPA has transported fresh sediment to “Tonne E3” in the North Sea since 2005. The aim of transferring the sediment to the North Sea is to permanently remove fine sediments from the upper tidal Elbe, thus permanently relieving the system of surplus silt. It is not possible to transfer the sediments into the Hamburg area (Neßsand) in the months from April to November for reasons of water protection. In that period protected fish species are spawning there and hydrological conditions (oxygen content, currents) are generally unfavourable at that time as well.

Double strategy: Clean up sources of pollutants and remove polluted sediments from the river

Hamburg has defined the target of reducing the pollution load of the Elbe and its sediments. In this way, the HPA makes a significant contribution to easing the burden on the Elbe and the North Sea.

To prevent new pollution, experts from the HPA pursue a strategy of cleaning up sources of pollutants (contaminated sites) directly on site along the course of the Elbe. To this end, they work with the Elbe River Zone Community (FGG), the International Commission for the Protection of the Elbe (IKSE) and the project “Elbe Sediment Pollution Clean-Up (ELSA)”.

Sediments which already contain a higher level of pollution are removed from the river system in Hamburg. For this purpose, the HPA has developed, at substantial expense and with significant scientific work, environmentally-friendly technologies for handling polluted dredged material. While most of sediments which are regularly dredged from the Port of Hamburg can be put back in the river at a different location, approx. 20% of more heavily polluted sediments are brought ashore and safely disposed of there. They are treated in the MSPS plant (mechanical separation of port sediments) and then dumped.