By Alison Freeman
BBC News, London
Gardens can seem like gold dust if you live in London.
Parking spaces can be attractive to house buyers
That elusive little bit of green where you may be able to soak up the summer sun - for a few weeks of the year at least - and even enjoy a sense of outdoor living can make a potential home all the more desirable.
But more and more of us are concreting over our front gardens either to create car spaces which avoid the cost of on-street parking, or simply to make them easier to maintain.
But environmentalists, and water companies, are against this trend claiming it adds to the problem of flooding.
Hilary Bennett, of Thames Water, said problems occur when the grass and earth is replaced and the rainfall runs off into man-made underground drains instead of soaking away naturally.
"We do find that since more front gardens have been levelled off, water from them races into the surface water drainage systems.
"London has a combined drainage and sewer system so all this water can overload the sewers.
"This in turn can flood out of manholes in roads, private connecting drains in properties and then flood gardens and even homes with foul water which contains untreated sewage."
But Simon Waller, senior sales negotiator at the Shepherd's Bush branch of estate agents Winkworth, in west London, said he would estimate a parking space could potentially increase the value of a house by £5,000 to £10,000.
It can also save a potential buyer the cost of applying for planning permission and the building work entailed in adding a drop kerb.
But if a house buyer does not own a car, the space could prove worthless, he said.
Mr McCarthy uses his front garden for mulching cuttings
"Of course, it depends on the location of the property and if you've got a nice car that needs to be parked off the road.
"It obviously decreases the insurance payments on your car so perhaps we could look to the insurance industry to do something about it.
"A garden is one of the most significant things you consider when you value a property because of the English obsession with the outdoors, but unfortunately a front garden is of no material value."
Donnachadh McCarthy, author of Saving the Planet Without Costing the Earth, says he believes his front garden, in Camberwell, south London, has actually increased the value of his property because it improves the way it looks.
He said: "I've got a wall creeper and a hedge and in the space between the wall and the hedge I mulch cuttings which also produces a little bit of food because wild garlic grows there."
He added: "It makes the house look much more inviting and friendly. Everybody who comes here thinks it's a lovely little cottage when it's just a two-up two-down."
The drive to concrete over front gardens to provide a parking space was "destroying nature's natural drainage system, which leads to flash flooding", Mr McCarthy added.
"These are the green lungs of London and when they go it destroys the streetscape."
Mr Waller says that in Shepherd's Bush the cost of installing a drop kerb can cost as much as £2000.
Added to this is the cost of the planning application and installing and buying the paving stones.
The cost of a residents parking permit in the area is just under £100 for 12 months, so to a buyer a ready-made space can be financially attractive in the long run.
'Worsening the problem'
The London Assembly's environment committee is calling on the government to bring in legislation which would limit the number of gardens that can be turned into paved areas.
But Jennifer Bates, the London campaign's co-ordinator for Friends of the Earth, says concrete gardens are just part of an overall problem which needs to be addressed.
She said: "As hurricane Katrina has showed us, and as the experts predict, we are experiencing more extreme weather events and we need to be cutting carbon dioxide emissions that are contributing to global warming.
"Clearly concreting over gardens or putting in more non-porous surfaces is just going to exacerbate flooding problems.
"We are going the wrong way," she added, "We are worsening the problem from all ends."