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Information - NH4.4 Rainfall induced landslides and debris flows (co-listed in GM)
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Event Information |
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Rainfall is the most common triggering factor in slope stability. Both shallow and deep landslides can be triggered by rainfall, with different frequency and under the effects different types of storms. For example, shallow landslides, and especially soil slips and debris flows in alpine and prealpine areas are triggered by intense rainfall, whereas shallow landslides in clayey soils are more sensitive to events of long and moderate intensity. As a consequence, rainfall analysis is the most frequently adopted approach for forecasting the occurrence of such phenomena. According to the type of the involved slope instability phenomenon different approaches have been presented. Rainfall thresholds, hydrological models and coupled methods have been used. Rainfall thresholds are also commonly adopted for civil protection purposes and to establish alarm networks in endangered areas. Different rainfall thresholds and hydrological models have been proposed in the literature. Among these relationships and hydrological models, it is possible to find some important differences that are sometimes neglected in their application. Most of the proposed thresholds and models are related to shallow landslides along open hill-slopes or hollows but they are sometimes incorrectly adopted to forecast channeled instabilities. The need for different thresholds is therefore evident especially when considering channelized debris flow. Most of these relationships determined for catastrophic events with occurrence of tens or hundreds of instabilities are adopted to forecast single or recurrent slope failures. Again, soils subjected to specific conditions (dry areas or periods, wildfire areas, etc.) can undergo temporal or definitive changes. According to different hydrological models, the basis of a complete approach is that soils or rock masses respond differently in function of their geological, physical, mechanical and hydraulic characteristics. Furthermore, morphologic and anthropogenic features control superficial, sub-surficial and deep groundwater flow and they can strongly influence both slope stability and triggering conditions. These problems and the hydrological or coupled hydrologic-mechanical -morphological models suggested for landslide rainfall triggering are the main interest of this session. Empirical, semi-empirical and deterministic methods or observations are the main concern of this session as well unambiguous case histories making clear reference to landslide type, rainfall conditions, soil and rock characteristics, role of vegetation, wildfires and anthropogenic disturbance in controlling slope stability. The same interest is reserved for the possible relationship between rainfall event, characterized by intensity and duration(etc.), and the size of the landsliding event (number, size, density or intensity of slope failures). The spatially distributed application of these models is one of the recent development and authors presenting papers on this topic are invited to participate to the session.
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Preliminary List of Solicited Speakers |
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