Embankment of The Mudflat
In Friesland and Groningen plans were made to embank and drain the Wadden Sea. As a result, the islands would have become part of the mainland. As of today, nature and environmental movements have been able to prevent this.
The only plan ever to be carried out was the construction of a causeway from the Frisian Holwerd to Ameland, in 1872, which was not very successful. Shortly after construction, the causeway had already suffered so much storm damage that the dam was abandoned in 1882. The dam has been almost entirely eroded since then.
In the northern Wadden Sea building dams proved to be considerably simpler. Nordstrand is now so much linked to the rampart by dikes that one can't really call it an island anymore, and also Langeness, Oland, Nordstrandischmoor, Hamburger Hallig, Sylt, and Rømø are all reachable by dams. Mandø is even reachable without a dam by means of tidal road.
Read more about this topic: Frisian Islands