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WHEN THE WATERS RISE, THE BUILDINGS SIMPLY FLOAT

TECHNICAL & PRACTICE

You don't need to be Schrödinger's cat to recognise that sometimes the facts can alter depending on perception.

Indeed, very often the same object can take on different meanings in different circumstances.

In the setting of the Palm Islands in Dubai, reclaiming 440km 2 of land from the sea is generally held to be a futuristic (if somewhat aesthetically naff) development, whereby human ingenuity has enabled the development of hitherto non-existent land and provided high-quality accommodation for around half a million people. Considering New Orleans, on the other hand, Lord May used his 2005 Anniversary Address to the Royal Society to say that 'it is conceivable the Gulf Coast of the US could be effectively uninhabitable by the end of century' and advocated that we stop building on flood plains and recognise 'that some areas should, in effect, be given up'. Building on reclaimed land or building on 'ood plains? Similar problems, different perspectives.

The Dutch have just completed the bulk of their 30-year Deltaworks project, which is intended to ensure that the disaster of 1953 doesn't happen again. That event wiped out 150,000ha of land and killed more than 1,800 people - putting New Orleans in perspective. The little-publicised Oosterschelde storm surge barrier stands as a testament to human ingenuity, particularly given the Netherlands' continuing precarious relationship with nature. It is 3km long and cost 2.5 billion euros (£1.7 billion), but it reduces the risk of flooding to once every 4,000 years. Meanwhile, in London, there is concern that the 20-year-old Thames Barrier is obsolete and there's nothing we can do except curtail the folly of building on low-lying land.

The environmental group WWF suggests millions could be saved by stopping 'ineffective flood alleviation' and allowing the wetlands 'to function as the natural soaks of the rivers'. On one hand then, there is the perception that nature is something to be tamed, on the other, that nature is sacrosanct.

The positive and negative interpretations of flood risk and the effect of human action in either causing, or remedying, the problem indicate different views on urbanism and the task of overcoming natural risks.

Many urban design students in British colleges today seem to be designing for climate change. Accordingly, many are primarily interested in houseboat, pontoon or floating technologies as a way of escaping a deluge. For this generation, the efficacy - and the audacity - of flood defence technology like the Thames Barrier is questionable. After all, commentators - like James Lovelock - suggest that we've had it, and there's nothing we can actually do about it. Buying into the notion that protecting land for a large number of people is impossibly ambitious, schemes developed for floating communities often contain an anti-social element, whereby the very idea of developing flood defence infrastructure for the benefit of 'the many' is casually given up.

These floating communities simply wait for the low-lying land to flood.

There are, however, more humanistic aspirations on offer, shorn of environmental rhetoric. Floating architecture, after all, can offer the potential to build in otherwise inaccessible locations, and much of the new-found aspiration for living on and around water has been driven by property developers' profits on waterfront development.

Houseboats have existed for centuries, but the new generation of floating architecture is permanently moored (with the potential for relocation). Hertzberger's rather unattractive attempt at a floating house at Middelburg was the turning point for this genre, and now companies are cashing in. Dutch development company Dura Vermeer is designing a 'floating city' for 12,000 people near Schiphol Airport, and many other smaller companies and architects are starting to experiment with the technology. Factor Architecten, an Amsterdam design company, has already completed a scheme for 48 water-borne homes in Maasbommel; architect Tangram has designed 85 units at Dordrecht; and Aquaarchiteure has recently set up a proposal for 65 water-borne dwellings.

This is not new technology, but has certainly caught a particular moment in architectural expression in the Netherlands.

Tangram, for example, constructed 18 timber houses on flood tides at Schillingdijk near Amsterdam-Osdorp way back in 1999. Here though, the concrete basement level was firmly plugged into a neighbouring dyke and a concrete slab cast across two neighbouring units, creating a fixed platform for semi-detached dwellings. In this scheme, the water is allowed to flow around the dwellings but the structure is static. Similarly, MVRDV's Silodam in Amsterdam, begun in 1995, locates various dwelling types on stilts fixed into the waterbed. The difference between these examples and the new generation of floating houses is that, now, the structure is allowed to move up and down.

In Maasbommel, where some of the units have already been handed over, the house structure comprises a hollow concrete 'basement' with insulation built in. This void area acts like a ship's hull, providing buoyancy and stability, as the structures are anticipated to rise by some 5.5m from the lowest tide level.

The structure sits on piles that have been anchored to the ground and project above the water line at low tide, so that the building is high and dry and the balcony and substructure span across these foundation piles. When the waters rise, the buildings simply float, maintaining their location by sliding along the sheathing of two mooring piles driven into the water bed. Flexible connections and pumps resolve the drainage and mains-supply issues. Plans to install wave-powered microgenerators in future models are already under way, although it is rumoured that some people have requested motion dampers, predominantly for the unsettling movement caused by the wind.

More exciting projects, such as the floating roads designed by XX Architects, can be used to overcome the potential devastation that a flood might bring. These roads are constructed of lightweight standardised aluminium box sections filled with polystyrene, jointed together in lengths as a modern version of the Bailey bridge technology. The design incorporates a kerb upstand to act as a breakwater and can take traffic driving at up to 50mph.

However, these megastructure-scale developments are anathema to the West. Indeed, because the issue of climate change informs the debate in Western countries, even the Netherlands is shifting its perspective from one that challenges natural constraints to one of accommodation of these constraints. The Netherlands has begun a 15-year programme of buying up land along rivers and reserving it for flood plains - effectively, as Peter Edidin of the New York Times said: 'The Netherlands has strategically begun to uncreate itself.' Last year, the Rotterdam Architecture Biennale was themed 'The Flood' and its curator Adrian Geuze said: 'Since the Second World War, the Dutch have relied on technology for protection from the rivers and the sea. We are convinced that this is not a clever way to deal with reality, and three months after the exhibition closed, Katrina showed us the truth of that.' Tragically, this kind of spurious intuition could end up repackaging the heroic ambition of the Dutch polders and floating cities. Instead of the social ambition of the Zuider Zee, we may end up with the philosophical survivalism of Noah's ark.

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