COMMISSIONED REPORT Commissioned Report No. 052 Geomorphological changes and trends in Scotland: debris-flows (ROAME No. F00AC107A) For further information on this report please contact: John Gordon Scottish Natural Heritage 2 Anderson Place EDINBURGH EH6 5NP Telephone: 0131–446 2450 E-mail:
[email protected] This report should be quoted as: Ballantyne, C.K., (2004). Geomorphological changes and trends in Scotland: debris-flows. Scottish Natural Heritage Commissioned Report No. 052 (ROAME No. F00AC107A). This report, or any part of it, should not be reproduced without the permission of Scottish Natural Heritage. This permission will not be withheld unreasonably. The views expressed by the author(s) of this report should not be taken as the views and policies of Scottish Natural Heritage. © Scottish Natural Heritage 2004. COMMISSIONED REPORT Summary Geomorphological changes and trends in Scotland: debris-flows Commissioned Report No. 052 (ROAME No. F00AC107A) Contractor: Colin K. Ballantyne, School of Geography and Geosciences, University of St Andrews Background As part of its environmental audit programme, SNH is investigating changes and trends for natural heritage reporting and development of indicators. Changes in geomorphological processes are an integral part of the natural heritage. The aim of this report, part of a series on geomorphological processes, is to document and analyse trends in debris-flows. The term debris-flow refers to the rapid downslope flow of a mixture of debris and water, and is also used to refer to the tracks of individual flows. Movement is distinct from fluvial transport in that the entire sediment- water mixture undergoes flow en masse. Two types of debris-flow are widespread: hillslope flows, which occur on open slopes, and valley-confined flows, which originate in bedrock gullies.