DEPOLDERING NOORDWAARD

The Noordwaard is an area of 4,450 hectares - around 6,000 football pitches - that borders on the Biesbosch National Park in Brabant and the Nieuwe Merwede. In the area’s lively history, nature, water and humans alternated in determining the appearance of the landscape. Eliminating the polder increased the safety situation of the downstream area, because the river water can flow in and out of the Noordwaard during periods of high water.

Struggle for the land

Water has always been a determining factor in the history of the Noordwaard.

  • During the St. Elizabeth’s Flood in 1421 - one of the most dramatic moments in the history of Noordwaard - the productive agricultural polder was transformed into a gigantic inland sea at the place where nowadays the Biesbosch National Park is  located.
  • Over the course of time, the farmers gradually reintroduced agriculture to the area, helped by the natural growth of sandbars which could be used for grazing and farming.
  • The recurring floods during the 18th and 19th centuries gave the impetus for the construction of small polders, which were consolidated starting in 1935.
  • The closure of the Haringvliet estuary as part of the Delta Works in 1970 virtually eliminated the influence of the sea, as it blocked the ebb and flow of the tides.
  • After centuries of struggle against high water, in 1980 a single large polder was finally created: the Noordwaard.

The Noordwaard proves its worth

The Room for the River programme added a new chapter to this history. In 2009, builders began work on one of the largest measures of the programme: depoldering the Noordwaard. Within just 5 years, the Noordwaard has been re-designed and transformed from an area protected by dykes to an area open to high water. In the middle, a high-water channel was formed to drain the large volumes of river water to the sea. This involved lowering the dykes to create inlets and outlets for high water.

Water level reduction and return of ebb and flow

The Noordwaard drains river water through the new flood channel if the Nieuwe Merwede river rises to more than two meters above normal river level standards. The depoldering project reduces water levels considerably: by 6 centimetres at the opening of the flood channel at the city of Werkendam and by 30 centimetres at the city of Gorinchem, around 8 kilometres upstream. The open connections bring the depoldered Noordwaard once more under the influence of the tides.

Innovation together with nature

The area protected by dykes has decreased due to the measures taken. Most of the area is now protected by quays: lower quays are expected to face high water once every 100 years, while the higher quays were positioned at the 1,000-year flood line. A new dyke was built at Fort Steurgat. A stand of willows, called a ‘griend’ in Dutch, was planted outside the dyke to block the waves, making it possible to build the dyke lower than usual. 

 

 

CONSEQUENCES FOR LANDSCAPE, RESIDENTS AND BUSINESSES

The depoldering project had far-reaching consequences for the landscape, for the residents and for the largely agricultural businesses in the area.

Businesses – sustainable perspectives, whether inside or outside the polder

Prior to depoldering, 80% of the polder had an agricultural function: primarily crops but also some dairy farms and horse farms. The new flood channel is no longer suitable for agriculture while the other parts of the Noordwaard can still be used as before the depoldering. One of the objectives was to give farmers perspective on a viable and sustainable future. To this end, high quays were built on both sides of the flood channel, with a surface area of approximately 600 hectares.

Residents – Safe housing

Every resident of the area had the opportunity to continue living in the depoldered Noordwaard. As a precondition the houses and their foundations needed to be able to withstand a flood that could occur once every 25 years. As such, some homes in the area had to be rebuilt on terps to prevent flooding. It is also important that the residents are not surprised by floods: they should have plenty of warning signals to leave their homes. The residents  therefore regularly practice evacuations based on an evacuation guideline that the city of Werkendam has created especially for that purpose.

Landscape – New nature in a unique area

The depoldering of the Noordwaard has dramatically changed the landscape. One of the objectives of the depoldering was to restore the landmarks that have long been associated with the Biesbosch. Space has been set aside for nature along the banks of the restored streams and in the flood channel. The designers used the topographical maps from 1905 as a reference point. The flow of the river in combination with the working of the tides have given the Noordwaard a natural habitat unique in Europe. Furthermore, when during the winter water flows through the Noordwaard, the new flood channel provides a resting place for migratory water fowl.

Plenty of opportunities for nature, economic activity and recreation

Thanks to close cooperation with residents, businesses and other stakeholders in the area, the depoldered Noordwaard provides plenty of opportunities for nature, economic activity and recreation. In order to keep the unique area accessible to all of its users, the infrastructure is kept intact as much as possible. The roads in the high-water polders are suitable for cars, agricultural vehicles and cyclists. The roads in the low-water polders are primarily intended for agricultural vehicles and bicycles. During periods of extreme high water, the high quays will form the routes to evacuate the area.

The Noordwaard is an important link in the Room for the River programme, which works to build a safe and attractive Dutch river landscape.

DEPOLDERING NOORDWAARD (FLOOD PLAIN) IN FACTS AND FIGURES

The Noordwaard is an area that borders on the Nieuwe Merwede river, to the west of Werkendam and to the north of the Biesbosch National Park. Within just 5 years, the polder has been re-designed and transformed from an area protected by dykes to an area open to high water.

 

Activities

  • 4 million m3 of soil will be moved
  • 70 km of new quays and dykes
  • construction of 33 bridges
  • installation of 31 pumping stations and various hydrological constructions (incl. culverts and decking)
  • 50 km paved roads
  • construction of 4 parking lots

Effect

  • lower water levels by 30 cm at Gorinchem
  • lower water levels by 60 cm at the inlet in Werkendam
  • drain high water on the Nieuwe Merwede as far upstream as possible
  • drain the water downstream as far to the west as possible in the direction of the Hollandsch Diep estuary.

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