The Haringvliet was formed as a result of the extensive flooding event of 1216, which breached the dunes of
Voorne and created a deep saltwater inlet. During a second flooding event, the
St. Elizabeth floods of 1421, this inlet connected to the
Merwede and became an important estuary of the
Rhine and
Meuse rivers. It used to be ecologically rich, and its brackish waters, fed by both rivers and sea, supported a healthy population of
seals. It also provided an access point for migrating fish like
salmon and
sturgeon. As a result of the
North Sea flood of 1953 the Haringvliet was closed off by the Haringvlietdam. The Haringvliet lost its estuarine characteristics and became a freshwater lake. Because of that, the seals are gone and migrating fish can only enter the
Rhine-Meuse Delta through the busy and heavy industrialised
Nieuwe Waterweg. There are plans to permanently open a few of the Haringvliet sluices, to partly restore the ecosystem. ==References==