This report summarises the results of a working group put together after a series of landslides in the form of debris flows occurred in Scotland in August 2004, blocking three trunk roads. While debris flows occur with some frequency in Scotland, they only rarely affect the trunk road network or for that matter the main local road network but when they do they can have a major detrimental effect on the local economy (especially with loss of tourism) and there is a risk of injury and fatality. The 2004 events followed a period of sustained rainfall accompanied by intense localised storms. The working group aimed to determine a sustainable approach to the management of such occurrences in the future. It is important that maintenance and construction projects currently in design take the opportunity to limit any hazards or exposure by incorporating measures such as higher capacity or better forms of drainage, or debris traps. Some retargeting of maintenance actions, such as checking of gullies, ditches and catchpits, is considered worthwhile. Better forecasting of areas at risk because of the weather is also suggested. A flowchart for risk assessment is presented, followed by a consideration of the available options including 'do nothing', 'do minimum', 'do something 1' and 'do something 2'.
Abstract