forecasting for slopes
Scottish Road Network Landslides
In August 2004 Scotland
experienced rainfall substantially in excess of the norm. The rainfall was both
intense and long lasting and a large number of landslides, in the form of debris
flows, were experienced in the hills of Scotland. A small number of these
intersected with the trunk road network, notably the A83 between Glen Kinglas
and to the north of Cairndow (9 August), the A9 to the north of Dunkeld (11
August), and the A85 at Glen Ogle (18 August).
While major injuries were
avoided, some 57 people were taken to safety by helicopter after being trapped
between the two debris flows on the A85 in Glen
Ogle (see cover picture). The A85, carrying up to 5,600 vehicles per day, was
closed for four days. The A83, which
carries around 5,000 vehicles per day, was closed for two days; and the A9,
carrying 13,500 vehicles per day, was closed for two days prior to reopening.
The disruption experienced by local and tourist traffic, as well as to goods
vehicles, was substantial.
Figure 2.7 – View of the second and larger of the A85 Glen Ogle
debris flows, showing the sharp bend in the channel just above road level.
The need to act was
recognised by Transport Scotland and an initial study was commissioned and the
results published in the Summer of 2005.
The study dealt with the
the options for undertaking a detailed review of side slopes adjacent to the
trunk road network and recommending a course of action.
possible mitigation measures and management strategies that might be adopted.
an initial review to identify obvious areas that have the greatest potential for
similar events in the future.
Both the Technical Report
(Winter et al., 2005a) and the supporting Summary Report (Winter et al.,
2005b) may be downloaded from:
Also available from this web
page are links to reports on climate change which were produced in parallel with
the landslides study.
This work led to a second
phase which is ongoing; this includes the development of a system to allow a
detailed review of the network to be undertaken to identify the locations of
greatest hazard and for those hazards to be ranked and appropriate mitigation
and/or management measures to be selected.
The overall purpose of these
studies is thus to ensure that Transport Scotland has a system in place for
assessing the hazards posed by debris flows. In addition, the system will rank
the hazards in terms of their potential relative effects on road users. This
will ensure that the exposure of road users to the consequences of future debris
flow events is minimised whilst acknowledging that it is not possible to prevent
the occurrence of such events.
A consistent, repeatable and
reproducible system is required. This is especially important as a variety of
consultants is likely to be involved in the data gathering, analysis and
interpretation process. It is apparent at the outset that a unified system
acceptable to all of the major players in the industry is required.
It was thus recognised at an
early stage of the development of the work that the input of a wide range of
experts and stakeholders would be required in order for the studies to be
The study is led by the
following, who would be delighted to answer any questions and queries:
Dr Mike Winter, TRL Limited
Forbes Macgregor, Consultant
to Transport Scotland
Lawrence Shackman, Transport
Winter, M. G., Macgregor, F. & Shackman, L. (Editors). 2005a. Scottish
Road Network Landslide Study. Edinburgh: Scottish Executive.
Winter, M. G., Macgregor, F.
& Shackman, L. 2005b. Scottish Road Network Landslide Study Summary Report.
Edinburgh: Scottish Executive.