 Long-time residents of Lewes, in East Sussex, still recall with a shudder the great floods of 2000, which turned their high street into a river and forced hundreds of people to flee their waterlogged homes. Since then, only one property development has been built beside the River Ouse, a pair of semis - with a difference. They are raised, Thai-style, on stilts, 10ft above the ground, and 2ft above the highest recorded flood level. This is an example of architectural ingenuity Britain's housebuilders will need to employ to reconcile the need for new homes with the growing threat of floods.  "Even if the water rose as high as it did in 2000, it would still be several feet below the main house," says Steve Guthrie, 55, who lives in one of the semis with his wife, Marisa, 39, and their one-year-old daughter, Lana. "The worst-case scenario is that our car would get a good wash."  The fear of being woken up in the night with one's home awash with muddy water is becoming a reality for an increasing number of homeowners. With climate change being blamed for more extreme weather patterns, flooding is a growing risk across Britain - insurers have paid out ?4.5 billion to customers whose homes and businesses have been hit since 2000, a 200% increase on the previous decade.  Last weekend, as Britain was hit by gale-force winds and torrential rain, with up to six inches falling in 48hr in places, the Environment agency issued 33 flood alerts and 66 warnings. "One in six homes in England and Wales is at risk of flooding, and the latest UK climate-change data, and our science, shows that this risk is likely to increase due to rising sea levels and more frequent and heavy storms," says David Rooke, the agency's director of flood and coastal risk management.  The increase in the rate and severity of flooding in towns and cities has also been blamed on poor planning decisions that have all too readily allowed homes to be built on flood plains, as well as cheap design and the use of nonporous surfaces that don't allow excess water to drain away naturally.  all of which makes the stilt house a model for the future. Despite recent extreme weather, the worst Guthrie has had to cope with in the past six years is river water encroaching a few feet into the garden during spring high tides. "Thousands of houses are built every year that are at real risk of flooding," he says. "This shows you can build safely on a flood plain if you do it sensibly."  Guthrie bought the house in 2005, a year after it was completed. He had long harboured an interest in sustainable architecture and was living alone in nearby Brighton when a friend invited him to have a look at the newly built property out of pure curiosity. "I had no intention of moving to Lewes, but I thought it was fantastic looking over the river," he recalls. "I saw it in summer, when it is really at its best - the light is amazing - and I just had to have it."  The design was inspired by the industrial heritage of the town and its once thriving shipyards. The barrelshaped roof, made of zinc, is designed to last a lifetime. Then there are the huge steel posts that lift the building off the ground, giving a useful space underneath, with enough parking for both properties, as well as endless storage - a practical by-product of the flood-proof design.  The house itself is entered via an aluminium-clad walkway that leads into a roomy open-plan kitchen and living room. Upstairs are a second living room, with toweringly high ceilings and its own balcony and staircase, and two bedrooms. (There is a third on the floor below.) The master bedroom is ensuite and there is a family bathroom, while the second bedroom takes advantage of the high ceiling, with a mezzanine level that can hold a double bed. a decked balcony leads off the living room, which in turn leads, via a spiral staircase, down to the garden.  To make the most of the riverside location, the back of the property is entirely glazed, giving an uninterrupted view over the garden and across the river to the nature reserve on the far bank. as if a wall of windows were not enough, Lap Chan, the architect, added an internal atrium into the design, which floods light into the heart of the house. The family have a front-row view during Lewes's famous bonfirenight celebrations: one of the main blazes is lit directly opposite the house.  If they have their way, though, the Guthries will not be there to enjoy this year's event. Gardens with direct river access and tiny children are not the greatest mix, and the property has become a little too small for their needs - so they have put it on the market for ?825,000.  Steve's daughter Liberty, 17, spends part of the week with the couple while she studies for a-levels, and Skye, 23, the son of his ex-wife, who is studying engineering at Plymouth University, is a regular visitor. They also need office space for Marisa, who works from home as a small-business consultant.  another imperative is the need to raise some equity for an overseas project. Steve pl 