Landshaping an adjustable wildlife crossings system

Wildlife Crossings, Colorado USA

ZJA had experience with wildlife crossings in the Netherlands, known as ‘ecoducts’, but the challenge here was to come up with a flexible, modular system. The architects needed to find an ideal shape for both traffic and passing wildlife, which could be adjusted economically to the most diverse landscapes and circumstances. The basic form chosen by ZJA from which to make a parametric model was a surface curved doubly and in opposite directions, known as a hyperbolic paraboloid, commonly referred to as a pringle or saddle shape. Seen from one direction it’s an arch, providing optimal space for passing traffic, while from the other it’s a bowl, which with its raised edges protects wildlife against the lights, movement and noise of the motorway. Read more about the project

The shape and the creation of the shape

The parametric model made it possible to have the design fit perfectly into the specified test location, at the foot of the Rocky Mountains, in Vail, Colorado. It had to look as though the landscape itself had chosen to fold and open out in such a way that wildlife and cars could cross each other undisturbed.

The design principle of the ecoduct consists of two arched shapes. An arch (B) that spans the road and an arch (A) that, like a dish, protects the flora and fauna from the noise, light and movement of the traffic passing below it.

Arches A and B combine to make a spatial figure, known as a saddle or a hyperbolic paraboloid. It is a form with excellent structural properties, but difficult to create. We have come up with an invention to aid the production process.

Design and research

Although the ecoduct in Vail was not built, the combination of the parametric script and the free and flexible construction method remained intriguing. It is very much an area in which ZJA is interested and carries out research. In this case the result was a collaboration with Diederik van Veenendaal who, at NEST in Zurich, was investigating free-form roof structures made using textile formwork.

Research of various kinds is needed if you are to design and equip a given location in such a way that it is used optimally both functionally and aesthetically. Landscape, the urban environment, history, and a precise spatial and physical knowledge of the assignment and the location are all of crucial importance. 

For ZJA the technical and structural ‘back side’ of the design process cannot be completely contracted out, since it is here that opportunities lie for finding an optimal combination of the practical, experiential and future value of a design. In ZJA designs, conceptual thinking, structural inventiveness, the treatment of materials and the production process all come together.

The exploded view clearly shows the different elements of the building system. The great advantage of this system is that the mould and its accessories can be reused time and again. Yet every ecoduct can be different, depending on the circumstances found at the location.

The ecologist involved, Sjef Janssen, takes us on an unforgettable guided walk through this valley in the Rockies, at Vall. That experience inspired the shape of the ecoduct that we chose.

– Rob Torsing, architect-partner at ZJA



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