Developers are tempted to wipe out old streets because it can increase the area of a site and hence development density, giving them more profits, an architect says.
The convenor of the Urban Design Alliance, Vincent Ng Wing-shun, said guidelines were necessary to control this phenomenon.
Development density is controlled by plot ratio - gross floor area divided by site area - meaning floor areas can be proportionately increased with site area. The larger the site area, the more floor area can be built. Since building regulations say streets within a development site should not be counted as site area, developers tend to acquire the streets from the government and include them as site area, Mr Ng said.
Currently, developers do not have to apply to remove a street, although they have to pay a premium to acquire public streets. A spokeswoman for the Planning Department and Development Bureau said there was no regulation to stop developers removing streets.
A Town Planning Board member, Raymond Chan Yuk-ming, said the board would consider the issue of the removal of old streets if public concern was raised over the issue. But he said it was not compulsory for developers to study a street's value.
Mr Ng said removing streets made it easier to plan and design a development.
'The streets could be kept and treated as open space,' he said, adding that greening, coffee shops and open markets could be introduced to help revitalise streets.
He said guidelines for keeping streets of special values were necessary to enhance the quality of urban life.
In a renewal project at Staunton Street in Central, the authority's consultant proposed saving all five streets, most of which are a century old.
The redevelopment is split into three sites. To keep the old streets, the authority has reduced the development density of the most sensitive site and transferred the reduced floor areas to two other less sensitive sites. But the project is still facing public opposition because it will wipe out some tenement buildings in Wing Lee Street.