Making room for the river

Extended Waal Bridge, Nijmegen

With its 244-metre span, in 1936 the bridge over the Waal at Nijmegen was the longest arched bridge in Europe. Still today it offers a majestic view of the wide river landscape. In 2007 the major planning decision outlined in ‘Ruimte voor de Rivier’ (Room for the River) took effect, as a reaction to the floods of the 1990s and in anticipation of the consequences of climate change. At Nijmegen it meant, among other things, that the dike at Lent was moved and a secondary channel dug next to the river (known as the Spiegelwaal or ‘Mirror Waal’). This new arm of the Waal meant that the Waal Bridge had to be extended to make the leap to the far bank. ZJA won the commission to develop the design for the Extended Waal Bridge.

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While most river bridges are built to enable traffic to cross the water, the Extended Waal Bridge was built to allow the water to pass under the traffic. To express this fact in the shape of the bridge, the idiom of current and wear was chosen. A bridge shaped by the force of water and its scouring effect.

– Jochem Verbeek, project-architect at ZJA

A mirrored bridge over the Spiegelwaal

The thinking behind the Room for the River plan marks a radical break with the traditional Dutch way of dealing with water. Instead of making the river flow to the sea as quickly as possible between high dikes, the new plan is all about the need for water retention. Deeper flood plains, secondary channels and marshland: all are intended to reduce the danger of flooding.

The fact that this also creates new nature reserves and opportunities for recreation is plain to see at Nijmegen. Between the Waal and the Spiegelwaal is now a popular island, Veur-Lent, that can be reached by a number of new bridges. The Spiegelwaal is ideal for water sports.

Finding the shape, making the columns

A bridge deck without stays or an arch requires columns. Their shape has to be functional as part of the structure, but in this case their appearance was also intended to evoke the power of flowing water. Think of gullies in the sand on the beach, or boulders that have been given their smooth shape by the water flowing past them. ZJA made a parametric model in which all the forces and properties were linked together functionally. The software worked through thousands of variations on the design of the columns. Eventually the designers found a shape that not only supports the bridge and has the desired spatial and visual effect but could be poured on location.

The streamlined shape of the columns required unusual formwork. The huge columns were created in a frame of milled beams, clad with bent sheets of plywood. The reinforcing, pouring and finishing of the columns was carried out with great attention to detail. Formwork oil and rust might damage their surface. Precisely because the bridge was designed to be experienced mainly from underneath, the last of the blemishes were removed by hand. Particularly striking is the gently curving depression in each of the columns, just under the roadway. Clench your fist and watch a hollow appear in the inside of your wrist. It’s a detail in the concrete that evokes the forces at play by using a bodily image.

Winner of a Dutch Concrete Award 2015.

Architect: ZJA
Client: the municipality of Nijmegen

Principal: Consortium i-Lent (Dura Vermeer en Ploegam)
Consultant: Witteveen+Bos 
year: 2015

Project: #661



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