The use of physically based methods to locate the in site surveys in areas prone to rapid landslides

The application of physically based methods to areas affected by landslides requires the knowledge of geometric, geotechnical and rainfall input data. Once the geometric and rainfall data have been acquired, the geotechnical data are of relevant importance for the results obtained by method implementation. Indeed, if significant geotechnical data on the soil involved by landslides are not available, any methodological application is a simplistic exercise. To overcome this issue, in the preliminary stage, data from the literature - for soils similar to those involved in the landslides – can be used in order to localize the in-site investigations in areas potentially affected by landslides. The paper shows an application of the physically based method TRIGRS to an area affected by rapid debris flows for the susceptibility assessment. Firstly, TRIGRS has been applied using as input geotechnical parameters those available in literature and the zones potentially affected by similar landslides have been identified. Detailed in-site investigations have been located and carried out in the so identified zones. By means of the results of in site surveys and laboratory tests a reliable geotechnical slope model for the area has been created. Therefore, TRIGRS has been applied again to the study area using as input geotechnical parameters those obtained from the survey. The last application of the method provided the susceptibility zoning map of the area. The achievement of these results has been favored by the limited extension of the area and by availability of literature data for the involved soils.