Wednesday 5 October 2016

A unique bridge for bats by next architects

“A textbook example of how a functional object can at the same time serve nature.” This is how bat-expert Marcel Schillemans from the Dutch Mammal Society described the recently completed Vlotwatering Bridge in the Netherlands. What is the story behind this unique ‘bat-bridge’?

The ‘bat bridge’ is part of the Poelzone, an elongated area in the municipality of Westland between the existing towns of ‘s-Gravenzande, Naaldwijk and Monster. Along the waterway a new green recreational area has been realised, including a cycle route, natural banks and spawn sites for fishes. The design for the landscape was conceived by LOLA Landscape Architects to strengthen the existing ecological connections and to have the natural and recreational functions complement each other. The new Vlotwatering Bridge by NEXT architects was commissioned by the municipality of Westland and is part of this broader plan.

The bridge is made for slow traffic (pedestrians and cyclist) and cars to a private house. The Vlotwatering is a flight-route for the numerous different bat species that live in the area. Recently, summer roost have been found nearby the water. Moreover, as the newly designed water-banks will attract more insects, it is expected the bat population will further grow. Thus, a bridge over the water offers a unique opportunity to for a bat-friendly design: the concrete mass of the construction creates an optimal climate and an ideal habitat for these mammals..

In designing the Vlotwatering Bridge, we worked closely with the bat-experts Herman Limpens and Marcel Schillemans (Mammals Association - Zoogdiervereniging). A first and important step in the process was a programme of requirements for the bats. Ecological designs are often blamed for having a high degree of “geitenwollensokken” ­- a Dutch expression referring to a certain kind of idealism, perceived to be naive, theoretical (much talk, little action), and foolishly optimistic, and therefore not achieving its goals. Hence, at NEXT we knew that the key to success was in finding a new approach: inquisitive and based on research. Instead of starting from existing references or common solutions, we based our design on the ecological requirements.  With this project we wanted to take ecological design to the NEXT level. This was most challenging for all parties involved.

With a length of 25 meters, the bridge consists of a concrete arch that spans the entire Vlotwatering and marks the entrance of the Poelzone. At its highest point, the bridge curves to form an S-shape and offer a panoramic view of the area. To design a bridge that would simultaneously be a habitat for bats, it was important to distinguish between different species, as each one has specific needs. The design of the various stays is customized based on the type, function and location and resulted in three specific components, each providing a specific opportunity for bats:

-         Bridge abutment. At the north side the abutment functions as a winter stay.
-         Bottom deck. To accommodate stays for bats during the summer
-         Bridge balustrade. Similarly to the deck, the balustrade provides accommodation for the summer

To optimize the suitability of the bridge for bats, the structure is made out of concrete, which provides a stable and pleasant climate for bats. Moreover, the concrete’s material qualities, high strength, freedom of shape, and easy workability make it possible to make a distinctive bridge that fits within the environment and cycle path. On the underside of the bridge there are entrance slots that have a rough finish for a better grip. The slots are part of a pattern of grooves in the concrete arch.

The different types of accommodation that are incorporated into the bridge are visible in subtle way to the visitors of the Poelzone. The bridge’s ecological functions have been translated to attention-enhancing details, making the Vlotwatering Bridge into a unique project, for both humans and animals.

The Vlotwatering Bridge was completed in the beginning of October 2015.
More information about the project:

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