Yorkshire Geotechnical Group – Debris Flow Risk to Linear Transport and its Reduction

Synopsis

Fast-moving, rainfall-induced debris flow events are relatively common in the mountainous areas of the UK. Their impacts encompass the economic and social as well as the physical risk to infrastructure and people. The mechanisms of rainfall induced,fast-moving debris flows will be considered as they bridge between slow mass movements and flood phenomena. A series of case studies from Scotland and overseas will be described. A wide-ranging view of hazard and risk assessment will be delivered. It will encompass semi-quantitative regional assessment and quantitative site assessments of debris flow hazards and risks. Focussing on road networks to articulate the principles, the risks will be considered in terms of those that affect road users (fatality), road infrastructure, and the socio-economic activities that the network facilitates.

Debris flows often sever (or delay) access to and from relatively remote communities for services and markets for goods; employment, health and educational opportunities; and social activities. Specific forms of economic impact will be described as will the way in which their extent can be defined by the vulnerability shadow. A strategic approach to risk reduction will be used to illustrate how a clear focus on the overall goal of risk reduction can be achieved before homing in on the desired outcomes and the generic approach to achieving those outcomes. The effects of climate change on debris flow hazard and risk will also be considered in the context of likely changes to hazard frequency and/or magnitude and changes to risk.