Eastern Scheldt Estuary
The Eastern Scheldt Estuary is a tidal body of water 25 miles (40 km) long, with a salinity similar to that of seawater. Since the late 1980s, it has been cut off from its input of fresh water from the Scheldt River by dams, leading to its reclassification as a sea-arm rather than an estuary.
It has also been defended against seawater flooding by a storm-surge barrier. This was originally to have been a fixed dam to prevent any ingress of seawater at all, but there were fears that, with a dam of this type, the estuary would gradually lose its salinity, producing an adverse effect on its fauna and flora—in particular, there were concerns that it would end the large-scale mussel and oyster farming in the area and degrade the tidal flats and salt marshes that form an important habitat for birds. The government of the Netherlands therefore commissioned a movable barrier, the construction of which was completed in 1986.