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1 INTRODUCTION
1.1 BACKGROUND
In August 2004 some areas of Scotland experienced
rainfall substantially in excess of the norm, in some cases
in excess of 300% of the 30 year average August rainfall.
This rainfall was both long in its duration and locally
intense, resulting in a number of landslides. Both the
trunk and local road network were affected by these
landslides, notably on the A83 near Cairndow on 9 August;
the A9 near Dunkeldon 18 August.
Figure 1.1 - Landslide on A85 near
Lochearnhead, August 2004. Photograph © Perthshire
Picture Agency.
While these events did not result in either major injury
or fatality, 57 people were trapped by the landslides on
the A85 near Lochearnhead and were taken to safety by
helicopter; the A83 was closed for two days; the A9 for two
days and the A85 for four days. This resulted in
significant disruption and inconvenience to local, tourist
and commercial road users alike.
In the period since 2001 a number of other weather
related events have also resulted in trunk road closures.
Some of these are listed below:
- January 2005 - A9 Kessock Bridge, A9 Cromarty
Bridge, A87 Skye Bridge, M90 Friarton Bridge, A92 Tay
Bridge, A90 Forth Bridge - Closure due to high
winds
- 2004 - A95 north of Cromdale, closed due to
flooding
- 2001-2004 - A9 Slochd, A9 Dunkeld, A85 Glen Ogle,
A83 Rest and be Thankful, A83 Cairndow, A82 various
locations between Fort William and Inverness, closed
due to landslides
During the same period weather related events,
particularly localised flooding, badly affected the local
road network throughout Scotland. Further disruption
occurred as a result of the severe winds of January 2005,
when a number of exposed roads in coastal areas were
seriously damaged.
Following the landslides in 2004, the Scottish Executive
commissioned two studies to provide guidance on measures
that might reduce and manage the risks associated with such
events. The studies are:
- Study 1 (Landslide Study): To consider the risk
factors associated with landslides and their potential
affects on the road network. This study is being
undertaken in two parts, with Part 1 being due for
publication simultaneously with Study 2.
- Study 2 (Climate Change Study): To consider the
potential trends in climate change in Scotland and how
this may affect the road network.
While these studies are independent of each other, they
have been developed in such a way as to be
complementary.
Although heavy rainfall has been a major contributory
factor in recent events that have affected the trunk road
network, it is only one aspect of the weather that has the
potential to affect road users. Study 2, which is reported
here, has therefore considered the full range of weather
characteristics. This is to establish how the potential
trends in climate change may affect the assumptions about
weather that currently inform the design and operation of
the road network. From this recommendations can be made to
assist in reducing and more effectively managing weather
related risks.
1.2 TERMS OF REFERENCE
The Scottish Executive commissioned Jacobs Babtie via
the
BEAR Scotland Ltd Operating Company term
commission to undertake Study 2, the brief for which was
to:
'Undertake a desktop analysis of the potential trends in
climate change in Scotland and determine the detailed
implications for the operation and management of road
networks. This will consider all elements of weather to
include:
- Temperature
- Rain
- Snow and Ice
- Wind
- Fog
- Coastal Flooding'
As studies, research and modelling of potential climate
change trends is ongoing in many areas, the study team
included members of the climate change team at the Met
Office, who provided guidance on predicted trends in each
of the weather events identified.
From the outset, the importance of seeking wide
stakeholder involvement was identified, and key parties
within the Scottish Executive were involved in the study
through a series of workshops. This also included liaison
with external bodies, notably the Department for Transport
and the Highways Agency, to enable data sharing with
similar on-going studies.
In addition, the function of network management was
considered essential to achieve improved risk management
and to support this consultation was undertaken with:
- BEAR Scotland Ltd, the Operating
Company for the North-West and North-East trunk road
units
- Amey Infrastructure Services Ltd, the Operating
Company for the South-West and South-East trunk road
units
- National Driver Information and Control System (
NADICS), managed by the Scottish
Executive's Traffic Controller Unit
1.3 REPORT STRUCTURE
Section 2 of the report details
the methodology adopted for the delivery of the study,
including the basis on which predicted climate change
trends have been developed.
Section 3 of the report details
the current assumptions in the design and operation of the
road network as they relate to weather events, and outlines
the historical context that underlies these
assumptions.
Section 4 of the report outlines
the predicted climate change trends within each of the
identified weather events.
Section 5 of the report
considers how these predicted climate change trends may
affect the future design and operation of the road network,
taking account of the outcomes of consultations and
literature reviews undertaken.
Section 6 of the report
summarises the recommendations arising from the study.
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