The harbour, the protective dike, and drainage
For centuries the sea broke through the narrow isthmus rather regularly. In 1862 the sea broke through in two places. The northern breach was quickly closed by the currents that deposit sand, but the southern one, which is now Thyborøn Channel, developed so that it was possible the sail through the opening in 1868.
The result was an extensive erosion of the sea coast, which receded at the speed of between 15 and 20 metres a year. This was worrying and a commission was formed to find solutions how to stop the erosion. While this commission was working experimental groynes were built from 1875. The commission recommended the building of groynes along the whole stretch from south of Bovbjerg to Lodbjerg in the north, and they also wanted dikes to prevent new breaches and flooding.
A large number of these were built and the coast now only recedes about 2 metres a year. Relying on these measures Thyborøn started growing from the original 9 houses, and Thyborøn harbour was built between 1914 and 1917 in connection with groyne number 64, which was used as a pier for materials for the building of groynes.
In 1930 the number of people in Thyborøn had grown to 600 and even to 1200 in 1940, which made Thyborøn into full grown fishing harbour with 100 fishing boats and the relevant service jobs of a harbour.
Surveys of the coast proved that deep water was approaching land a worrying speed. It was feared that the groynes would collapse in case of several violent gales in succession. A new commission was appointed in 1937 and it recommended that Thyborøn Channel should be closed. Work was begun immediately on a 20km long protective dike from Flade Lake in the north to Langerhuse in the south. The Dike was to be with a sluice and also locks for the passage of ships. Besides that it was necessary to build proactive dikes around Agger, Thyborøn and Harboøre. Groynes number 59 and 72 must be extended to 1100 and 2100 metres long piers into the sea.
The work was stopped in 1954 because of the heavy costs. The figure shows the constructions that were completed. A storm tide broke through the isthmus at Vrist and since 1982 there has primarily been focus on the protection of the coast with sand pumped onto the beaches from the sea. This is part of an agreement between the state and the local communities as to who shall cover the costs of coastal protection. Feeding the beaches with sand has turned out to be an efficient way of stopping the sea from eating the coast.
The large enclosed area between groyne 54 at Thyborøn cross dike and groyne 33 at Harboøre is drained through a sluice at the northeastern corner.
Thyborøn harbour is still an important harbour on the west coast of Jutland and it is still developing. The harbour is a self-governing entity under Lemvig municipality focusing on development, quality and service. Most of the business is related to fishing, but also transport has risen over the last few years. Thyborøn harbour is known in particular for its high quality fish for consumption and for being the first place to have a fish auction that is based on using the internet.