De Biesbosch

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Air view over the Biesbosch area (8).

De Biesbosch, meaning 'forest of sedges', is one of the largest national parks of the Netherlands and one of the last freshwater tide areas in Europe. The Biesbosch consists of a large network of rivers and smaller and larger creeks with islands. The vegetation is mostly willow forests, with some grasslands and fields of reed.

The Biesbosch was created when 300 square kilometres of polder lands were submerged in the St. Elizabeth flood in the year 1421. Before this, the area was called Grote Hollandse Waard, containing cultivated land and a number of villages. The more than a century old dikes collapsed because of lack of maintenance, due to the difficult economic situation in the area, and the difficulties between the political entities within. Very high river levels combined with a severe storm surge coming in from the sea resulted in the flooding of most of the Grote Hollandse Waard. After the flood, three areas remained: the Island of Dordrecht to the west, the Land van Altena (with the city of Woudrichem) to the east, and the brackish swamps of the Biesbosch in between. Most of the area changed into a network of estuaries. The most important of those where the Hollands Diep and the Bergse Diep. Both were connected to the Haringvliet which existed before the disaster as a pure sea-water inlet of the North Sea. After the disaster it became brackish and an important estuary of the rivers Rhine and Meuse. A persistent misunderstanding is that the Biesbosch arose by this storm flood in one night. It is true that this flood broke dikes of the then Grote Hollandse Waard or Zuid Hollandse Waard, but it needed dozens of years before the whole area was under water and had changed to the Biesbosch with its creeks and reeds.

Biesbosch at low tide.

In the beginning the Bergse Diep was a shallow but extended body of water, with high tides but also a predominance of fresh water. The deposits of the rivers caused the waters to become only submerged at high tides. From that moment on the area was called Bergse Veld and later on the Biesbosch. A network of interconnecting creeks, mudflats and forested areas was created. It served as a sort of inland delta of the large rivers feeding it. A significant result of this was that the former estuary arms of the Rhine and Meuse, further north-west, were devoid of much of the inflow of fresh water. This caused the rivers to fill with deposits, so the important shipping route between Rotterdam and the inland areas was no longer usable.

In the last centuries conditions changed significantly. Most of the Biesbosch was reclaimed and turned into polders. The connection with Rotterdam was restored by blocking the build-up of deposits by artificial means. Most of the Biesbosch creeks were dammed-up to lower the risk of flooding. A shipping canal was created to distribute the flow of the rivers: the Nieuwe Merwede.

Before 1970 a connection with the sea existed, and the tidal differences were, on average, two meters. Due to the inflow of the Meuse and Waal rivers, fresh water continued to dominate. The tidal differences diminished to some 20-80 cm after 1970 when the Delta Works closed the Haringvliet and with it the Biesbosch's direct connection with the sea.

In World War II, the area was used by Dutch residents to hide out from the German occupation forces in the Netherlands. A resistance group was formed that, late in the war, captured Germans fleeing to the north from what was then the Allied-held south of the Netherlands. In the winter of 1944, the area was crossed by refugees from the occupied north, while, at the same time, it was being used to smuggle medicines to the north.