VAST AREAS of upland Scotland are vulnerable to landslides in bad weather, which is putting many of the country's vital arterial routes at risk.

A map produced by the British Geological Survey (BGS) shows that stretches of the A9, M74 and many other major roads pass through zones where there is a "significant" potential for landslides.

Yet a study promised four years ago by Scottish ministers to pinpoint the precise sites at risk has still not been completed - and the Scottish government has come under fire for its "lack of urgency".

The BGS map, provided to the Sunday Herald, shows that large areas of the Highlands and southern Scotland are at moderate or significant risk of landslides. These are places where scientists judge that steep slopes, underground fractures and other geological features make the land prone to slippage.

Among the roads in the high-risk areas are the A9 between Dunkeld and Drumochter and north of Dornoch, the A82 near Fort Augustus, the A84 south of Strathyre and the A93 to Braemar. Sections of the main route south from Glasgow, the M74, also go through landslip-prone areas.

When large amounts of rain fall on porous sandy soils and peat they rapidly become saturated. If they are underlain by rock or some other impermeable barrier, the water may have no escape and can literally liquify the ground.

On steep slopes this can trigger what geologists call a debris flow, resulting in many tonnes of mud and rubble moving far and fast down the hill. There have been about 175 major landslides in Scotland over the past 100 years, with an increasing number in recent decades.

The A7 near Langholm has been closed since 10 July, when torrential rain washed away part of an embankment, causing severe disruption to traffic. The A85 at Lochearnhead was closed for four days in August 2005 after two major landslides trapped 57 motorists.

After the Lochearnhead landslides, the then transport minister Nicol Stephen launched investigations "to identify potential trouble spots". But the final results are not now expected until the autumn.

Dr Richard Dixon, the director of WWF Scotland, said:"It is pretty hard to understand how it can possibly have taken the government more than four years to work out where the danger areas are, especially since the basic data is already available.

"That's four lost years which could have been used to set in place proper emergency plans and to begin to address the root causes of landslides in the most vulnerable areas. The people of Langholm will be infuriated by the government's lack of urgency on this issue."

Many experts think that landslides will increase because of the changing weather patterns caused by pollution. "The risk is certainly likely to increase, particularly in Scotland," said David Crichton, a visiting professor at the Benfield Hazard Research Centre at University College, London.

BGS landslide expert Dr Andy Gibson stressed that his organisation's map, which doesn't show roads or towns, could only give a rough guide to the hazards.

The Sunday Herald overlaid the road network on the BGS map.

Gibson said: "The low resolution map does not give enough detail to allow a viewer to make an assessment of hazard at a particular location."

A detailed picture of exactly which stretches of roads are at risk will have to await the publication of the Scottish government's report.

The government's Transport Scotland agency confirmed that its landslide study identifying the roads most at risk was due to be published in the autumn.

But it pointed out that the study wouldn't cover incidents like that at Langholm, because there the road had been undermined by subsidence rather than blocked by debris from a landslide.

A spokeswoman for Transport Scotland said: "The BGS data cannot be used in isolation.

"We have used this information as base data for our study, but this alone would not allow us to predict where landslips are likely to occur with any accuracy."

She said making accurate predictions was "extremely complex and time consuming".

"It requires very detailed assessment of specific locations, coupled with sophisticated modelling of ground and climate conditions.

"The work that Transport Scotland has been taking forward is recognised internationally and, so far as we are aware, no other roads authority in the world has undertaken studies to this level."