ABSTRACT
The rapid movement of large volumes of surface materials under gravitational influences adds considerably to the range of hazards found in mountainous terrain (Hewitt, 1992). For example, many large glacial lakes exist in the Himalayas. Those held behind ice-cored moraines can create outburst floods, capable of generating massive flows of 30,000 m3sec1 with run-out distances over 200 km downstream, which threaten lives and expensive infrastructure like roads and hydro-power plants (Richardson and Reynolds, 2000). The rapid mass movements cause most loss of life and damage, whilst slower movements are costly because of damage to property. Depending on the dominant material, mass movements can be grouped into landslides (rock and soil) or avalanches (snow and ice). Major movements are triggered either by seismic activity or atmospheric events. Some of the largest disasters have been earthquake-related (see Chapter 5). Waste material from industry can also produce hazardous mass movements. In 1966, 144 people – including 116 children – were suffocated at Aberfan, south Wales, when coalmining waste slid down a hillside to overwhelm the village.
