Snow avalanches in Scotland, with particular reference to the Cairngorm Mountains
The thesis describes a method for predicting avalanche activity in Scotland, based primarily on meteorological and topographical data, and this is incorporated into a framework for avalanche forecasting. A literature review identifies the main meteorological and topographical factors causing avalanche release. Snow accumulation, cold temperatures or thaws are identified as the major meteorological factors causing avalanches, and the thesis so distinguishes two basic avalanche types---the direct-action avalanche caused by fresh snow accumulation, and the climax avalanche caused by temperature changes. Slope angle, surface roughness, slope geometry and catchment area are identified as the major topographical controls on the location of avalanche activity. The thesis presents data on avalanche activity in Scotland over the last two hundred and eighty years, with particular emphasis on the Cairngorm Mountains. Avalanche locations, types and magnitudes for almost a thousand avalanches are described. Data on Scottish weather and terrain conditions are also presented, also with particular emphasis on the Cairngorm area. Major periods of snow accumulation, cold temperatures and thaws are identified between the winters of 1977/78 and 1979/80, and the location of steep slopes, smooth surfaces and large catchment areas in the Cairngorms is described. Data on the characteristics of the Scottish snow cover, based on work performed in the Cairngorms by E. Langmuir, B. Beattie and the author are then presented. Correlations between avalanche activity and meteorological, topographical and glaciological conditions are demonstrated, and this enables a predictive model to be developed which assesses avalanche probability on the basis of the amount of fresh snowfall and the prevailing temperature. Fresh snowfall of 200 mm., and either several days of cold weather with maximum temperatures below -4°C or two or three days of warm weather with maximum temperatures above 0°C lead to avalanche activity. The model can be continually up-dated and permits a continuous avalanche probability assessment to be made.