Little is known about the island Bosch, al we know is that it was property of the ‘van Aduard’ Monastery until the year 1530. During the Middle Ages, Bosch was located between Schiermonnikoog and Rottumeroog. During the All Saints day flood (Allerheiligenvloed) in 1570 it largely disappeared in the sea. Repairs of the sea wall were not an option and the entire population evacuated.

Allerheiligen by Moser, 1570.

It remained as a sandbank until the Christmas flood of 1717. After this flood, the island Bosch was completely washed away by the sea.

The Christmas flood of 1717.

TV-TAS, that is what all the Dutch children learn as a study aid for the five Dutch Wadden islands (in English better known as Frysian Islands). It stands for Texel, Vlieland, Terschelling, Ameland and Schiermonnikoog. But once there was a sixth island. It disappeared in the early 18th century due to a flood. The island was called ‘Bosch’.

The island Bosch, with Frise (Friesland) to its south (map is upside down).

It was always known that the island of Bosch once existed. Many maps showed its presence. The Sunken History Foundation was founded after a pilot project about the island Bosch in 2005/2006. In 2008 the geologists Karel de Vries and Albert Oost of the Sunken History Foundation found the first real evidence of its location. By using ground radar they found at a depth of 3 metres different ground deposits. Because of the island's movement, Schiermonnikoog now lies above the former island Bosch.

Ground radar image of the beach of Schiermonnikoog.

The movement of the Wadden Islands

The Wadden Islands are constantly moving. The most important movement is called ‘walking’: the islands are moving from east to west. Due to this process, islands disappear slowly into the ocean in the West, while large sandbanks appear in the east. This so-called walking is also the main reason why all the island towns locate themselves on the West side of the island. But when these towns were founded, they usually lay in the middle of the island. Due to this, many towns and villages disappeared into the sea during the last centuries.

The movement of Bosch and Schiermonnikoog from 1500 till 1990.

• Wikipedia on Bosch (Dutch).
  Wikipedia.
• Sunken History Foundation.
• Wikipedia about the Wadden Islands (English).
  Wikipedia.
• Buursma, A. & H. Feenstra (red.) (2006).
  Bosch, eiland in de nevelen van de historie: Bosch boven water gehaald.
  Stad & Lande 15, nr 2.
  pp 4-33.