Rest and Be Thankful

Rest and Be Thankful is the highest point on the A83, separating Glen Kinglas from Glen Croe. It is also one of the places in Scotland with the highest risk of landslides and debris flow hazards, which has increased in recent years due to the frequency of heavy, intense and prolonged periods of rainfall. Transport Scotland has a method of systematically assessing and ranking the hazards posed by debris flows which is described within the Scottish Road Network Landslide Study. From this assessment, the A83 Ardgarten to Rest and Be Thankful is amongst the most highly ranked debris flow hazard sites in Scotland.

Transport Scotland prioritise safety for all road users and we are aware of the A83's importance as the primary route to Argyll. The A83 Route Study was undertaken to identify and appraise potential options to minimise the effects of closures.

Our objectives were:

• reducing the impact on journey times by reducing the frequency and duration of road closures caused by landslides
• reducing the economic impact to the A83 study area by reducing the frequency and duration of road closures

Transport Scotland has invested £4m in taking forward a programme of landslide risk reduction measures as part of the 'Red Option' at the Rest and Be Thankful. This includes developing local diversion routes and moving forward other recommendations from the route study.

Reducing the risks of road closure

Transport Scotland has developed a number of ways to mitigate landslide effects near Rest and Be Thankful.

• We monitor landslide prone areas by various means to help reduce the risk to road users and gather information for our research to help us learn more about landslides.
• We may introduce physical measures to help to reduce risk of landslide debris reaching the trunk road.
• We have to manage landslide risk on all of our trunk roads in Scotland.
• Sometimes we need to close the road if the safety of road users is compromised by landslide debris or a risk of debris reaching the road. We may have to divert road users under these circumstances.
• We keep road users informed of higher risk and where there is a diversion in place by various mediums.

In the event of a landslide it may be necessary to close the A83 at Rest and Be Thankful. To help road users plan their journeys in the event of a closure, we created a [leaflet (LINK: road closure leaflet)] to provide information on the steps we will take to reopen the road.

When any trunk road is closed due to an incident such as flooding or landslides, a standard incident diversion route is implemented. These routes are agreed in advance with the police.

The A83 at Rest and Be Thankful was closed for a total of 41 days on twelve separate occasions since 2007. The standard incident diversion route at this point utilises sections of the A82 between Tarbet and Tyndrum, the A85 Tyndrum to Dalmally and finally the A819 between Dalmally and Inveraray before rejoining the A83.

This diversion route journey time is typically 66 minutes which is an increase in 31 minutes and an increase in distance of 25 miles between Tarbet and Inveraray using the pre-planned diversion route.

The 'Red Option' is Transport Scotland's method of mitigating landslides at the Rest and Be Thankful. We considered a range of options which could help minimise the frequency and duration of road closures. The Red Option, as outlined below, provided a similar level of benefits to other options for a significantly lower costs over the same time period.

What's involved?

The Red Option consists of a range of hazard risk reduction measures proposed along the line of the existing road. The works will include:

• additional fencing
• debris netting
• drainage improvements
• enhancement to slope vegetation
• culvert improvements

During these works, the Old Military Road below the A83 was available as a local diversion route as required. The works continued until the measures implemented demonstrated a sufficient level of protection to the A83.

Progress

All phases of the Red Option debris netting are now in place. During the landslide event on 5 December 2015 during Storm Barbara, our debris nets were successful in preventing approximately  1,000 tonnes of debris from reaching the trunk road.

A 2015 study, undertaken by AECOM consultants, to assess the performance of existing risk reduction measures considered historical and recent landslide activity. The outcome of this study made recommendations on further improving the existing risk reduction measures over a range from High to Low frequency of each phase.

The current package of works encompasses the highest frequency events identified in the study and invited options from tenderers for special structure solutions to provide the additional protection at Phases 5, 7 and 9. The returned tenders included options for more debris flow netting and catch-pits. The tender offering the catch-pit solution was assessed as providing the best solution to reduce the risk at the high frequency channels and the best whole-life cost. The tender was awarded on 24 February 2017 on the basis of a catch-pit solution at each of the high frequency channels.

The planting of vegetation and forestry on the hillside, upslope of the A83 Trunk Road, is in the design and planning stage within the Forestry Commission, which will further reduce the risk of landslides. The benefits here will only be realised around 15 to 35 years after planting.