PLANS are being drawn up to plant 250,000 trees on the slopes above the A83 to prevent landslips that have closed the road eight times in the past five years.

According to experts, the roots of the trees would bind the soil and also help heavy rainfall soak down into the ground rather than running off towards the road, taking part of the hillside with it.

Since 2009 the Scottish ­Government has invested £4.9 million to combat the problems on the road, which runs between the head of Loch Long and that of Loch Fyne.

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This includes the construction of a local diversion route at the Rest and Be Thankful.

But twice since it opened, the A83 has been closed by landslips further north, and the diversion was unable to be used. Motorists were again left with the options of a 50-mile detour using the A82 to Crianlarich and Tyndrum, or travelling by way of the Gourock to Dunoon ferry.

Transport Scotland is still ­seeking a long-term solution and is working with Forestry Commission Scotland (FCS) and local landowners to develop a strategy.

A spokeswoman said: "Tree planting to help stabilise the slope above the A83 is one of many options being looked at. We have established this would have to be done in conjunction with other measures and are discussing this with our stakeholders."

Syd House, FCS's regional manager for Perth and Argyll has been working on a plan. He said there was plenty evidence from the likes of the Philippines, Brazil and California that showed when there is deforestation and the vegetation is removed, intense rainfall would wash considerable amounts of soil away in landslides.

Mr House added: "In addition, the Alpine countries have long recognised the importance of protection forestry. That is woodland established to protect villages and communities from land slippages and avalanches. They manage the forests simply to protect the asset. It is exactly that principle we are talking about for the A83."

He said many different things could be done for the road.

"Hard engineering, netting, clearing rock faces are being looked at by Transport Scotland. However, tree planting would contribute to the long-term solution. We are talking about something that will help stabilise the slopes over the next 20,30, 50 years, indeed in perpetuity," he said.

"It wouldn't be commercial ­conifer forestry because that would involve taking the trees off at some point. Nor would it involve heavy ploughing or drainage.

"We are talking light touch. We are talking about native species and those that are particularly good at binding such as hazel, willow, hawthorn, aspen alder, birch, maybe oak. The deeper the roots, the more they can bind the soil," he said.

But, he said, if the soil was shallow and the water got between it and the rockface, it would not matter whether trees were planted or not as the ground would still slip.

However, tests of the land at the A83 suggest there is enough soil

He added: "The initial project would be about 247 acres, planting about 2500 per hectare, so about 250,000 trees."

He said there was also another theory for the landslips. With land grazed by livestock such as sheep over centuries there was a compaction of the soil. The top 6in could be wet, then after that it is quite dry.

This led to the water coming off the surface more rapidly, rather than soaking downwards, thereby contributing to landslips. "But trees would help the ground act like a sponge," said Mr House.

If the tree planting proved successful on the A83, then a similar project could be tried on other landslip prone areas in the West Highlands, the Great Glen and Glen Ogle above Lochearnhead, he said.