The Northern European Enclosure Dam is a proposed solution to the problem of rising ocean levels in Northern Europe. It would be a megaproject, involving the construction of two massive dams in the English Channel and the North Sea; the former between France and England, and the latter between Scotland and Norway. The concept was conceived by the oceanographers Sjoerd Groeskamp and Joakim Kjellsson., the scheme is largely a thought experiment intended to demonstrate the extreme cost of engineered solutions to the effects of climate change. The scheme's authors describe it as "more of a warning than a solution".
The northern enclosure would be a multiple section dam at the perimeter of the northern rim of the North Sea. The detailed engineering is not stated, although some form of continuous structure could provide for overland infrastructure - road and/or railway between the Great Britain and Norway.
The eastern section of the North Sea Dam would offer the greatest engineering challenge of the whole NEED project, stipulated to a length of 331 km through open water and with the sea floor depths exceeding 300 m in the Norwegian trench. The dam would origin from the eastern shores of Mainland, Shetland, just north of Lerwick, heading east to Bressay and Isle of Noss to allow for the shortest ocean crossing towards Sotra island in Hordaland on the western coast of Norway. The ocean floor east of Shetland dives down to depths below 100 m just 1 km off shore, and then continues fairly flat through Bressay Ground and Viking bank for some 210 km, until the deep incline of the Norwegian trench. Here, being the latter part of the sea crossing, the sea floor reaches some 321 m depth within 5 km from the western Norwegian coast were there is a steep incline.
Norwegian internal waters
For the NEED to work, Norwegian internal waters have to be enclosed as well, as the Sotra terminus of the North Sea Dam is an island. With the shortest distance for the crossing from Shetland, the dam will reach the western shore of Sotra, just off Telavåg. The final part of the enclosure would therefore have to be the crossing of the narrow, but deep sound separating Sotra from mainland Norway close to Bergen. Several alternatives are viable, one being the route crossing the 1 km wide and some 140 m deep Lerøyosen sound from southern Sotra, the islands of Lerøyna, Bjelkarøyna and Storakinna to the seemingly mainland south of Hjellestad, a total distance of 5 km. As the latter lies on an island, the very narrow Ådlandstraumen would have to be closed, in order to make a complete enclosure. A more northerly route from Sotra would cross the 650 m wide and 90 m deep Kobbaleia sound, the islands of Tyssøyna and Alvøyna, and finally the 1 km wide and 100 m deep Raunefjorden sound to the mainland just off Flesland, Bergen International Airport. There is also a possibility that Norway would include an enclosure of Bergen, which have faced many floods in recent years, and in that case the first part of the enclosure dam would be between Sotra and Askøy, and the second between Askøy and mainland Norway crossing Byfjorden north of the city center of Bergen.