Scottish Road Network Landslides Study - University of Glasgow

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INTRODUCTION
The overall purpose of these studies is thus to ensure that the Scottish Executive has a system
in place for assessing the hazards posed by debris flows. In addition, the system will be
capable of ranking the hazards in terms of their potential relative effects on road users. This
will allow the future effects of debris flow events to be managed and mitigated as appropriate
and as budgets permit. This will ensure that the exposure of road users to the consequences of
future debris flows 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 will be involved in the data gathering, analysis and interpretation
process. Inevitably each will have a different, but nonetheless valid, approach when operating
independently. Such a situation would make any comparison between individual consultant’s
results and recommendations impossible for the purpose of, for example, allocating funds on
a priority basis across the network. 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
completed successfully. In particular, the agreement and input of those most likely to be
responsible for using the system was required.
A Project Workshop was held in order to capture the knowledge vested with individual
experts (see Appendix). The Project Workshop was facilitated by Professor Malcolm Horner
of the University of Dundee and comprised presentations given by acknowledged experts
followed by focussed discussion sessions designed to open out the knowledge base and
determine the way forward with the project. Following the Project Workshop the Editors
assigned tasks to individuals in terms of the preparation of this report as exemplified by the
authorship of individual sections. The main results from the Project Workshop are
incorporated in the various sections.
Section 2 gives the background to the Study as a whole. It describes the different types of
landslide, focussing on debris flows as recently experienced, and illustrates the recent history
of debris flows in Scotland with examples right up until the present. It also deals with climatic
issues and those issues which relate to third party ownership of land from which landslides
may originate
Section 3 examines sources of relevant information, including previous literature, the Project
Workshop and available data sets from sources such as the Scottish Executive and the British
Geological Survey.
Section 4 deals with the classification and type of debris and other types of flows. It explains
how rapid landslides develop from their causes and the underlying soil failure mechanisms,
through the mechanics of their downslope propagation and, finally, to their run-out at the base
of the slope.
Section 5 examines the relevance of the key factors in debris flow initiation and propagation
that have been identified from past events, including the events of August 2004. These are
considered in terms of factors affecting the likelihood of debris flow occurrence, including
the effects of run-out, and factors affecting the exposure of road users to debris flows