Glossary

Discharge, or headwater discharge, refers to the amount of water (measured in cubic metres per second) that flows from the upper Elbe to Hamburg. The more it rains in the Elbe region, the higher the discharge. Water abstraction and the management of reservoirs in the Czech Republic also influence the discharge volume.

The average annual discharge over the last 30 years was 652m³/s. In the particularly dry last eight years, however, it was only 484m³/s.

The higher the discharge, the less sediment has to be dredged in Hamburg, as more mud and sand is washed towards the North Sea.

Before dredged material can be moved to a new location in the Elbe or the North Sea, a comprehensive study and prediction of the potential impact on the environment will be carried out. The new relocation site may only be used if this study proves that the planned relocation will not have any significant adverse environmental impact. This will ensure that all legal protection requirements are always met.

Fine-grained loamy soil that has settled over the centuries with the tides in the marsh, i.e. in the coastal area. Clay is also used in dyke construction or for making bricks.

The closer a relocation site is to the port of Hamburg, the faster the dredged material is washed back to where it was recently dredged by the stronger tidal current. With low runoff, i.e. dry conditions in the upper Elbe region, it only takes a few weeks for a large part of the dredged material to be returned from the Neßsand relocation site on the Hamburg state border. Our aim is to minimise this recirculation dredging by transporting more dredged material further towards the North Sea and preventing it from returning. This can also reduce the overall dredging volumes in Hamburg.

If the dredged material is too contaminated to remain in the Elbe, we bring it ashore and treat it in our processing plant. There, it is separated into clean sand and contaminated, dewatered fine material and then safely disposed of in our dredged material landfills.

These are places in the Elbe or in the harbour that are no longer deep enough for shipping due to the deposition of sediments, i.e. mostly mud and sand.

Extensive scientific investigations at and around the relocation sites while they are in use. Water and soil samples are taken, for example, and fish, snails and mussels are also tested for contamination. Monitoring ensures that undesirable effects on the environment are recognised at an early stage so that effective countermeasures can be taken quickly.

The German abbreviation stands for  "mechanical separation of harbour sediments". We have been reprocessing Elbe sediments in this plant for almost 30 years.

The Nautical Centre, opposite the Finkenwerder ferry terminal,  monitors and controls Hamburg's shipping traffic on the Elbe and in the port. It also sends the pilots to the large ships and determines the draughts and conditions under which the ships can call at the harbour and terminals.

Sediments are small particles from the water that settle to the bottom of a body of water due to gravity. They consist of sand, silt, even smaller clay particles and plant remains that have decomposed over time.

Sedimentation refers to the deposition of sediments on the water bed, i.e. the formation of sediments.

Sediment management refers in particular to dredging and relocation to ensure sufficient water depths. However, the remediation of pollutant sources along the Elbe up to the Czech Republic or structural measures that favourably influence the currents are also important parts of holistic sediment management.

Mud is a natural component of the water and consists mainly of fine-grained sediments, i.e. clay and mud, as well as organic components such as algae, bacteria or plant remains. When this combination of suspended matter settles to the bottom of a body of water, silt is formed.

Suspended matter are all particles that are kept suspended in the water for a certain period of time by the currents. This allows them to be transported over long distances. If the current decreases, the suspended matter sinks with gravity to the bottom of the water, they sediment or become sediment.

The flood, which pushes the water towards Hamburg, almost always has more force and pumps more muddy material upstream than is washed back into the North Sea at low tide. This pumping effect is all the stronger the less water flows down the Elbe, for example when the summers are very dry.

Riparian forests are typical small, dense forests along the tidal Elbe that line the riverbanks and are influenced by the tides. They are very rare throughout Germany and are therefore specially protected.

The influence of the North Sea extends far inland. From the estuary in Cuxhaven to the weir in Geesthacht, the Elbe is subject to the fluctuations of the tides. This 160 km long section is therefore also known as the tidal Elbe. Tid is Low German and means time.

After the excess sediment has been dredged, it is transported in the hopper dredger's hold and returned to the water at another location via bottom flaps. These locations are known as relocation sites. They are extensively checked beforehand. This ensures that their utilisation does not have any undesirable effects on the environment or other uses.

Water depth maintenance, also known as maintenance, ensures that the depths once created in the harbour basins and in the Elbe are permanently maintained. Just as a road has to be cleaned and repaired after it has been newly built, it is the task of water depth maintenance to constantly ensure that excess sediment is removed by dredging so that ships can call at their berths unhindered. Land treatment is also an important component of the complex water depth maintenance in Hamburg.

Hydrography is concerned with the measurement and description of the physical properties of oceans, seas, coastal areas, lakes and rivers.

Hydrology is the study of water. It deals with all manifestations of the element, as well as its physical, chemical and biological properties and the associated influences on the environment.

Estuaries are funnel-shaped estuaries that are under the influence of the tides, such as the tidal Elbe.

The fairway is the part of the Elbe that is intended for shipping. It runs through the centre of the fairway and is constructed in such a way that ships can navigate there safely - with prescribed minimum depths and widths.
In the Elbe, however, the fairway only covers part of the entire width of the river. The deepening of the Elbe therefore did not affect the entire river, but only this section, which is particularly important for ships.