Coastal protection
The narrow isthmus between the sea and the Limfjord has been broken many times over the years. In 1862 it happened again, even in two places at the same time. The northern breach was soon closed with sand again and by 1875 it was closed completely, but the southern hole developed and became Thyborøn Channel.
The high level of wave activity along the west coast results in massive transport of sand and gravel along the coast. The new channel and the fact that the Limfjord is a huge reservoir made it possible for tidal floods to run into this reservoir, so that the wandering materials along the coast were now deposited in Nissum Bredning. This resulted in serious erosion of the coast outside Thyborøn and the coast receded nearly 20 metres a year.
In 1984 this process was so conspicuous that people were worried. That is why the building of groynes along the isthmus was started. Groynes cannot stop the coast from receding, but they can reduce the speed. Since then protective dikes and reinforced dikes have been built in certain places in order to protect infrastructure against erosion and flooding.
Groynes and dikes protecting infrastructure
In 1981 there was one of the worst storm tides ever and the dike was broken at Vrist. As a result of the storm tide the work at establishing a flood warning system for Thyborøn and at securing the town against flooding from the Limfjord was begun. By 1983 real contingency plans were in place. Security work against flooding by raising road levels was also carried out in the 1980s.
The coastal authorities and the municipalities came to an agreement about the costs of protecting the coast through 5-year-plans. The primary measure taken today against the erosion of the coast is a method of replacing the sand eaten by waves and currents with new sand pumped from the sea. This seems to be the only method that can stop the sea from eating the land. On the whole isthmus from Harboøre to Agger this requires about 400000m3 of sand every year.