Saturday, March 19, 2011

Staying above water

From: Financial Times

By Richard Warren

Published: March 18 2011 22:00 | Last updated: March 18 2011 22:00

A floating home in the Netherlands

Cees Westdijk at his floating home in Maasbommel, the Netherlands

As pictures of devastation in Japan continue to dominate the media, Prince William begins his tour of Australia to meet victims of last December’s river floods. These grim reminders are something many of us need to heed. Just as nuclear power is being re-evaluated in the light of Japan’s disaster, flood defences need to be re-examined.

A forecast by the Intergovernmental Panel on Climate Change (IPCC) that sea levels may rise 59cm by 2100 appears conservative, because it does not factor Nasa-funded research published this month, which indicates that ice around Greenland and Antarctica is melting at an accelerated rate. To combat these threats, architects are designing flood resistant homes, floating islands and even cities on water.

The Dutch are leading the way. In Maasbommel, construction group Dura Vermeer has built 50 floating homes that can rise 5.5m in a flood while staying dry inside so utilities work normally. Hollow concrete bases keep the timber homes afloat. The company is working on several projects for clients at home and abroad to produce hundreds of its newest type of floating house, which is partly submerged with a concrete and expanded polystyrene (EPS) base that insulates against cold water temperatures.

Architect Alexander Henny’s firm, Aquatecture, designs floating homes for individuals living on Amsterdam’s canals. Henny says the search for solutions to the problem of rising sea levels has helped his business survive the recession.

Projects are growing bigger. Dutch architects have created designs for possible water cities in their own country while developer Dutch Docklands said it would create five floating islands for the Maldives government by 2015. The $500m project includes golf courses and a 61ha star-shaped, floating convention centre.

In Rotterdam harbour, Dura Vermeer and fellow Dutch company, FlexBase, have built the Floating Pavilion. Its designers, DeltaSync, see it as a vanguard for more ambitious projects.

“The Floating Pavilion is a pilot project for sustainable flood-proof urban development,” says Bart Roeffen, DeltaSync’s creative director. “The key towards floating urbanisation is to become less dependent on the shore in terms of utilities, parking and infrastructure. The Floating Pavilion is almost fully self-sufficient.”

DeltaSync is looking into how to create floating cities in harbours, as well as in open sea locations. “Floating urbanisation can provide more urban space in these increasingly densely populated areas, in a safe and sustainable manner,” says Roeffen.

‘TSUNAMI-SAFER’ HOUSES

When a 10-metre-high tsunami devastated the northeast coast of Japan on March 11, it was hard to imagine how any building could resist such a force. But in Sri Lanka homes are being built that are designed to do just this. The Prajnopaya Foundation charity is building 1,000 replacements for homes destroyed by the tsunami of 2004.

These “tsunami-safe(r)” homes were designed by scientists at the Massachusetts Institute of Technology and architects at Harvard Design School Tsunami Design Initiative group.

Dr Gopal Madabhushi, reader in geotechnical engineering at Cambridge University, who tested this design in laboratory wave tanks, says it could survive a tsunami like Japan’s.

“We are allowing the water to pass through the building,” says Madabhushi. “The pressure on the structure should not increase substantially. It is only when you try to stop the wave that the pressure would increase too much.

“The building has large windows and doors facing the direction from which water comes, allowing water to go through the building. The doors and windows get blown away, leaving the main structure as it is.”

“It really does not matter how high the wave is,” says Madabhushi, “Our tests had the wave higher than the building.”

These developments must be low-rise so floating platforms remain stable, says Johan van der Pol, deputy director of Dura Vermeer’s research arm.

Half the Netherlands lies below sea level, so the country’s long experience of coping with floods means its architects have been quick to design for rising sea levels, says van der Pol. However, even the water-conscious Dutch government must change its approach if architects’ solutions are to be realised, he says. It only compensates home-owners who suffer flood damage if they are inside the ring of dikes, not outside, even if the homes outside float, like those at Maasbommel, he says. Maasbommel’s floating homeowners can get building insurance, however.

The public must change its perceptions too. We pay a premium to live by water – up to 30 per cent in central London, according to estate agents Knight Frank – but most of us are loath to live on water.

“When living in amphibious homes you know there could be a rise of sea water levels, so the perception is that you are expecting a threat,” says van der Pol.

British architect Pippa Nissen offers a solution to negative perceptions of water-living – build flood-proof homes on land. Her studio has created designs for Flood House, a two-storey home that would allow occupants to continue living there during floods. Water would be allowed to enter the ground floor where a 1m-high concrete dado wall could be “easily” cleaned after a flood. The kitchen, bathroom and living room would be on the upper floor where self-contained utilities, including an electricity generator and water storage, would continue to function. Flood waters must rise beyond 2m before the upper floor would be inundated.

“We identified that it had to be a house on the ground,” says Nissen. “People perceive that as being better than a floating home or a house on stilts, which are thought to be a bit wacky.”

In New York, the focus is on creating flood-proof structures. Building codes upgraded in 2009 require developers of some new buildings in flood-risk areas to construct functional parts of a building up to 3ft above maximum flood levels by placing them on stilts, elevating lower floors or creating spaces where flood waters can flow. “There’s a very small population of buildings where you have to design on stilts,” says James P Colgate, assistant commissioner at the Department of Buildings. “Most of the buildings are designed for still water. When the water comes up to a certain level and when it leaves, that event should happen without an insurance claim and without damage to the building or people.”

Buildings designed to cope with flood in New York include 201 Pearl Street, Manhattan, a 28-storey residential and retail building extension to 2 Gold Street designed by architects Avinash K Malhotra. Flood-control features include thick walls and shields that come down in front of doors to stop water from entering the building.

Flood prevention measures are expensive to implement and so New Yorkers, like the rest of us, will be paying more for shops, offices and apartments in the years ahead. It’s a small price to pay.

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Flood protection schemes: Dubai to Venice

Measures adopted globally to protect against rising sea levels range from soft engineering options such as adding sand to beaches, to hard engineering, including flood barriers.

London: The Thames Barrier is the main protection until 2070 when it will be upgraded or replaced. Eight smaller barriers in east London, plus walls and embankments, complete the city’s defences against a sea level rise of 2.7m.

New York: Revised building codes make new developments more watertight in flood-risk areas. Measures range from constructing buildings on stilts to strengthening walls.

New Orleans: A $14.45bn revamp of sea defences includes toughened levees and 8m-high concrete walls to protect against a one-in-100-year storm. The city’s Lower Ninth Ward may flood in severe storms, so water-resistant houses are being designed.

Sydney: The Coastal Councils Group published a report in December 2010 proposing sand-mining at sea to replenish beaches that would otherwise be eroded at 10cm per decade.

Venice: A system of flood barriers located where Venice lagoon meets the Adriatic is designed to cope with 60cm rise in sea levels. Due for completion next year.

St Petersburg: A 25.4km flood barrier, due to be completed next year, will protect the city from a one-in-1,000-year flood with surge of 4.55m. The £1.8bn project doubles as a motorway.

Dubai: State-owned developer Nakheel factored 30cm-50cm rise in sea levels by 2100 when creating the Palm Jumeirah and the World archipelago reclamation projects.

Singapore: Singapore’s Marina Barrage, opened in 2008, will keep out seawater from low lying urban areas.

Netherlands: Sand has been dredged from the seabed and piped ashore to extend shoreline and build dunes. The height of existing dikes has been raised and new barriers built. A temporary “river” will flow through designated areas, including a 1,000ha flood zone, during severe storm surge. Rivers widened where they meet sea.

Maldives: Artificial, 188ha island created in 2004 and five floating islands scheduled for completion by 2015. Most vulnerable islands may be abandoned.