The soil covering much of Britain, especially in southern England, has a high concentration of clay. And “drier summers can lower the water table, which in areas with clay soil can cause the ground to dry out and shrink. In severe cases, this can lead to subsidence. Similarly, wetter winters can lead to flash flooding,” said Chris Wilford, associate director of PRP Architects, an international practice based in Surrey that has studied the effects of climate change.
Roger Minost, a Sussex architect who works in Britain and France, said that such problems had brought new complexity to house design and construction and that they were not limited to the British Isles.
“To avoid problems, we now go much deeper than we did when I first started working 30 years ago,” Mr. Minost said. “Then, we used to go down about 600 millimeters — now it will always be deeper than a meter, sometimes even more.”
“In France,” he added, “I tend to work in rocky areas, where the climate change issues are more to do with water from flash flooding — but there are some pockets of clay. What we are now seeing more and more in both places is round holes being drilled deep into the ground and filled with concrete before building begins.”
Peter French, a civil engineer and managing director of Canham Consulting in East Anglia, said flooding was also becoming a bigger issue for British homeowners because demand has led to construction in more flood-prone areas.
The Environment Agency released data in January showing that more than half a million homes in Britain are at significant risk from floods and that protecting them will cost as much as £1 billion, or almost $1.6 billion, a year by 2035.
“When you design drainage systems you design them for the worst case scenario, which is the ‘one in a hundred years’ storm,” Mr. French said. “Now, however, we have to expect higher levels of water more often and are being told to improve our design standards by 30 percent.”
The increase in development, and the covered surfaces that go along with it, also have been blamed for the rising amounts of runoff during storms.
An example would be Much Wenlock, a Shropshire town, where exceptional levels of rainfall in 2007 led to damage to at least 64 properties.
John Yeats, a former district and town councilor and a member of the Wenlock Flooding Forum, said that the town had traditionally recorded high levels of rainfall but that he believed that climate change and increased construction had exacerbated problems.
“The drainage systems are inadequate, he said. “A lot of water runs off into the streams and down over the drains, resulting in floods.”
The former mill that now is the home of Paul Weeden, a retired geography lecturer, is one of the residences in Much Wenlock that have been inundated three times in the past 10 years. The first flood destroyed his kitchen, and the second left every room on the ground floor filled with about 15 centimeters, or 6 inches, of water. Plaster had to be stripped to a meter high, solid floors were laid and waterproofing was installed.
“The third time was in 2007 and the water came up to two-foot high,” Mr. Weeden said. “Most of the proofing on the walls stood up to it but all the electrics downstairs had to be stripped out and we had to live upstairs for six months while repair work was carried out.”
Liam Hanlon, director of Forshaw Group, a Liverpool firm that does repair work for insurance companies after floods, said business had increased as major climatic events take their toll on buildings.
“We see all kinds of problems from subsidence with foundations and damage to external areas, such as drainage,” he said.
“This is becoming widespread. We need to look at where we are building new houses and the infrastructures we have in place for dealing with these problems.”
Jason Wakeford, a spokesman for the Environment Agency, part of the Department for Environment, Food and Rural Affairs, said the organization was considering these issues.
“We have powers in the planning process — if we think a building project could exacerbate flooding or is in a high risk area in the area then we can get it called in by the secretary of state, and reviewed,” he said. “There will always be building on flood plains — the Olympic site is at flood risk — but it is a case of looking at systems to reduce the risk while also maintaining flood defenses.”
He said the agency had called for insurers to require more work at sites damaged by floods.
“We are calling for higher-tech solutions so that buildings are quicker to dry out and people can get back into their homes more quickly,” he said.
Angus Middleton, an engineer with Renaissance Regeneration, a British environmental consulting firm, said the increasing power of the wind could also be a threat to residences — creating more lateral pressure on structures and requiring stronger foundations — even as it adds to Europe’s wind energy resources.
“In the future, more people will certainly need to take steps to protect their homes and surveyors will need to be a bit more thorough when making their reports,” he said.
It is a view echoed by English Heritage, an organization dedicated to protecting the country’s historic environment.
Renee Fok, a spokeswoman, said climate change could accelerate the deterioration of construction materials.
“Most historic buildings are resilient and adaptable,” she said, “but extremities in weather caused by climate change do pose some concerns.”
The source article A Flood of Challenges in Building for a Changing Climate - NYTimes.com was published October 28, 2010 by NYTimes.com .