Exeter has a long history of flooding, going back as far as the 13th century. The current flood defences were built in the 1960s and 70s after devastating flooding affected more than 1,000 properties. Although the current defences have worked effectively over the past 40 years, studies carried out by the Environment Agency indicate that in a more extreme flood situation the current defences would not be able to protect vulnerable parts of the city. The new £32M scheme is designed to reduce flood risk to more than 3,000 homes and businesses in the heart of Exeter. Downstream of Exeter city centre, major works include a flood relief channel and weir designed to increase capacity during high river flows. Within the city centre itself and specifically along the historic quayside, the new flood defences comprise permanently fixed steel posts between which removable barriers will be installed when the flood risk is high. A planning condition to the scheme required these industrial-style posts to be covered by ‘sleeves’ in a traditional bollard style, in keeping with the built environment of the Riverside Conservation Area in which The Quay is located.
Main contractor BAM Nuttall approached Furnitubes’ designers to discuss the feasibility of various material options, with the challenges being not only the aesthetic appearance of the sleeves but also the practical lifting operation given its height and weight, and a locking mechanism to prevent the sleeves being removed by the public, whilst still being easy to remove by Environment Agency staff when the flood defence barriers need to be installed. With the flood defence posts standing at 1.35m high, it was immediately apparent that the sleeve solution would need to be lightweight to be comfortably lifted off the post, leading to the decision to pursue a design in plastic. As a moulded material plastic also lends itself to creating the kind of ornate detailing typical on cast iron bollards that the sleeves were required to mimic. The design of the sleeve was highly complex, with the assembly comprising two purpose-made rotational mouldings (for which new tooling was made), connecting stainless steelwork and also a discreet locking mechanism, and with several special variations to deal with variable ground level conditions along the quayside.
The Quay remains open to local traffic so a tough plastic is an ideal material in the event of a low speed vehicular impact – sufficiently robust not to deform from light impact but not so hard to cause serious damage to a vehicle. Plastic also has the benefit (over steelwork) of offering greater corrosion resistance in this potentially aggressive marine environment.