Rock Avalanches’ Morphological Classification: Important Tool for Risk Assessment

Well-grounded and timely assessment of risks provided by hazardous phenomena in mountainous regions is an important factor of their sustainable development. Rock avalanches are among most critical due to large volumes, extreme mobility, ability to block river valleys. Assessment of risk produced by rock avalanches that will occur in such regions in future inevitably, requires prediction of the exposure that can be treated both directly—as size and shape of the area that might be affected by moving debris, and indirectly—by estimating height and shape of natural dam that could be formed in narrow valley, that predetermine magnitude of inundation and of the potential outburst flood. Such assessment can be performed using statistical relationships between initial slope failure parameters—volume and slope height, and resultant parameters –runout and affected area, derived for rock avalanches of different types. Their morphological classification takes into account the confinement conditions, debris distribution along travel path, directivity of debris motion. Further division within the selected types considers additional morphological and geotechnical factors such as shape of the deposits in plan view, interaction of rapidly moving rock avalanche debris with substrate and with obstacles. Future efforts should be concentrated on compilation of the uniform worldwide rock avalanches database allowing statistically representative analysis for each type and subtype selected according to the proposed classification system.