DHI addressing wave problems in Danish port

In recent years, the harbour at Thyborøn has been experiencing increasing problems with large waves in the approach channel, waves that have been overtopping the outer structures that provide protection to the harbour and to vessels using it.

This being the case, the harbour has, in collaboration with DHI, launched a study to determine the cause of the problems and what can be done to reduce wave problems in the harbour and eliminate overtopping of the breakwaters.

According to DHI Group spokesperson Peter Sloth, the problems particularly arise during and after periods with strong westerly and northwesterly winds. In conditions such as these, the waves outside the entrance channel can reach 3 to 4m of significant wave height.

Since it is a fairly recent phenomenon, a study carried out by DHI has initially focused on why the problems have arisen and included an analysis of the historical development of the bathymetry in the area, an analysis of wave climate variations in recent years, and simulation of the wave transformation from the North Sea and into the harbour based on current bathymetric conditions and conditions prevailing 4 to 5 years ago.

The study has revealed that bathymetry at the outer part of the entrance channel and just outside the harbour has changed. The water depth has been reduced in an area outside and north of the harbour and at the same time the water depth has increased along the eastern side of the channel.

As a consequence of changes in the bathymetry, waves from the North Sea propagate in a different way – towards the harbour instead of passing it. Investigations to clarify what can be done in the future to address this issue are now under way.