What’s a fisherman without a safe harbour to come home to? In Hvide Sande on Denmark’s western coast, the local fishermen are facing a problem: their harbour entrance is not only too shallow for modern fishing vessels but regularly obstructed by sediment, some times for weeks at a time. DHI applied its modelling tools for a new design of the harbour’s entrance and to plan the accompanying dredging activities.
Hvide Sande is a picturesque fishing village on Denmark’s exposed North Sea coast with little more than 3000 inhabitants and approximately 60 fisheries vessels. Fishery is a major source of income, for the fishermen themselves and the associated processing industry as well as a major attractor for the tourism sector.
However, Hvide Sande Harbour faces some problems. The natural depth of the sand bars bypassing the harbour is only 2.5 metres, not sufficient to accommodate today’s fishing vessels that require a minimum depth of 6.0 metres. Moreover, heavy sedimentation in the harbour’s access channel, especially following storm events, hampers the safe passage of vessels and ships. Therefore, the authorities wished to increase navigation depth in front of the harbour while at the same time reducing sedimentation in the access channel.
Aerial view of Hvide Sande Harbour with the current harbour design.
In an innovative approach, DHI managed to solve all these problems in one go. DHI’s concept consists of a combination of new protective breakwaters, embracing the harbour entrance, and capital dredging of the coastline north of the harbour, where the deposited sediment usually originates. The streamlined breakwaters result in an increased flow velocity past the harbour mouth, thereby reducing sediment deposition in that area. Dredging of the coastline in the updrift area further helps to maintain the required water depth. The approach builds on a combination of DHI’s advanced morphological modelling tools and a large set of field data: Hourly wave, wind and water level measurements, as well as weekly soundings of the harbour access channel, allowed for a thorough calibration and validation of the models.
Formation of sand bars with the current (left) and the new (right) harbour design.
As a result, Hvide Sande Harbour is spared double trouble. DHI’s solution significantly reduces dredging requirements as well as downtime due to inaccessibility of the harbour. The effect is far-ranging: In the new harbour, fish can be landed during all weather-conditions, guaranteeing the supply of local fresh fish. Fishermen do not need to find another harbour to land their fish, saving them precious time and money. All in all, the new harbour, under construction as of June 2011 and scheduled to be completed by fall 2012, will help to maintain a small fishing community in a rural environment, receiving the local fishermen in its safe embrace.
Compare the old and the new harbour design, and see the resulting changes in the navigation channel:
http://www.youtube.com/watch?v=JivcrR1l9nU
http://www.youtube.com/watch?v=qTaCRMqeewg