Recent avalanches and landslides experienced in the Swiss Alps during the first half of 1999 have demonstrated the need for further advancements with respect to understanding and assessing the various hazards associated with mountain slopes. Although considerable effort and resources have been expended towards these problems in the past, their complex nature have often resulted in studies limited to individual phenomenon. Thus it is proposed that a detailed investigation be performed directed towards qualitatively and quantitatively assessing the interrelationships between the different controlling factors responsible for inducing slope mass movements. Furthermore, a key aspect of this proposal would be to bring together researchers from varied fields to communicate to each other the relevance of the different controlling factors (i.e. geology, hydrology, biology, etc.) to the overall assessment of natural slope hazards.

When examining the different types of mass movements acting on a mountain slope (e.g. avalanches, rockslides, mudflows, etc.), it becomes obvious that a large number of processes are involved. Geological, geomorphological, hydrological, atmospherical, geomechanical and numerous other physical based processes, all contribute in one form or another to mass movements. In effect, these processes may be viewed within a system through which slope movements occur as the result of a continuous series of events linked through cause and effect relationships. This concept leads to the following three-step approach:

Given the complexity of the system (i.e. a mountain slope may be viewed as a system within which these processes are interacting), some methodological device is required to allow for a coherent and practical evaluation of the different physical interactions involved. One of the objectives of this study, is to provide a systematic means to assess these factors with respect to their interaction with one another and their overall influence on generating different types of mass movements. For example, such an assessment could be initially derived through the development of an interaction matrix, in which the key processes and their responding interactions with one another are defined:

Such a matrix system can be expanded to include several key processes in which both binary and higher level interactions are evaluated. Furthermore, these evaluations would consist of both qualitative and quantitative measures, which would be defined based on the intensity, complexity and dominance of specific interactions.

After defining the various key interactions, consideration will then be given to their sensitivity to various triggering mechanisms. Slope instabilities may have several causes as defined through the interacting processes, but only one trigger. By definition, a trigger is an external stimulus such as an intense rainfall or snowfall, earthquake or rapid snow melt that causes a near-immediate response in the form of a mass movement by rapidly increasing the stresses or by reducing the strength of slope materials. In some cases mass movements may occur without an apparent trigger because of a variety or combination of causes, such as chemical or physical weathering of materials, that gradually brings the slope to failure, although in such cases "time" may be viewed as a trigger.

By defining and evaluating the different short- and long-term triggering mechanisms and their effects on the previously defined process interactions, it will then become possible to assess the types of slope instabilities to be expected for a given slope. In this sense, a final output from the study will be the development of an interactive tool that combines data base information (e.g. GIS, physical properties, etc.) with measurable site-specific quantities (e.g. precipitation amount, seismic load, etc.) to compute the types of hazards to be expected in mountain-slope environments and to assist in forecasting the likelihood of their occurrence.

To assist in developing such guidelines, another key aspect of the study will be the use of several representative test sites with histories of multiple slope-hazard occurrences. These slope sites are to be selected and used to provide key information and controls with respect to both individual and interrelated hazard mechanisms (e.g. slopes susceptible to landslides in clay/marl rich sedimentary formations; slopes prone to rockfalls in fractured crystalline rock; etc.). Through these site studies, valuable insights will also be gained in terms of data collection and management, as well as such long-term factors as human interaction (e.g. land development, deforestation, etc.) and the role of changing global weather patterns.