This paper presents recommended methodologies for the quantitative analysis of landslide hazard, vulnerability and risk at different spatial scales (site-specific, local, regional and national), as well as for the verification and validation of the results. The methodologies described focus on the evaluation of the probabilities of occurrence of different landslide types with certain characteristics. Methods used to determine the spatial distribution of landslide intensity, the characterisation of the elements at risk, the assessment of the potential degree of damage and the quantification of the vulnerability of the elements at risk, and those used to perform the quantitative risk analysis are also described. The paper is intended for use by scientists and practising engineers, geologists and other landslide experts.

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The relations between the angle of reach (fahrböschung) and other indexes expressing the mobility of landslides and vertical drop, horizontal reach, and volume of landslide mass have been analyzed by means of simplified plots and regression equations. Results for 204 landslides of all sizes show that whatever the mechanism of motion, all kinds of landslides experience a continuous reduction of the angle of reach with volume increase. This reduction starts from the smallest sizes. Scattering in this relation is mostly due to mechanisms of motion and to both obstacles and topographic constraints on the path. This synthesis indicates that small landslides (less than 0.5 × 106 m3), in relative terms, display excesses of travel distance similar to large landslides. Since most small landslides are not expected to develop any change in the mechanism of progression while moving, the decrease in the reach angle with volume suggests that scale effects should be taken into account. The angle of reach is found to be a proper indicator of the relative mobility of landslides and is not dependent on the height of fall. Key words: mass wasting, landslides, reach angle, runout distance, rock avalanches, shallow landslides.

More and more natural disasters are being reported worldwide, particularly with respect to landslides. They cause injuries and deaths and induce physical, environmental and economic damages that hamper the development of wealthy as well as poor countries and regions. It is therefore necessary to include consideration of landslide hazards in land use and emergency response planning for public safety and realization of safe engineering projects. It is essential for authorities to have appropriate maps describing hazardous areas at their disposal. It is also important that they are aware of the different steps within a coherent approach that lead to the identification of landslide areas, the evaluation of the corresponding hazards, and the assessment of the risks these assessments imply. A large number of distinctive methods for landslide hazard mapping have been tested and applied in different contexts for more than 30 years. Many of them have been presented in recent international conferences such as the International Symposium on Landslides (Rio de Janeiro, 2004), the International Conference on Landslide Risk Management (Vancouver, BC, 2005), or the International Forum on Landslide Disaster Management (Hong Kong, 2007), all of them organized under the auspices of the JTC-1, the joint ISSMGE, IAEG and ISRM Technical Committee on Landslides and Engineered Slopes. The JTC-1 recognizes that there is a need for unified terminology in susceptibility, hazard and risk zoning, so that zoning in any area could be compared on a similar basis with zoning of adjacent areas, and to insure that fundamental assessment steps are properly considered and applied in the management of landslide-prone areas. JTC-1 also recognizes that the time has now been reached when quantitative hazard and risk zoning is possible. With this in mind, JTC-1 appointed a Scientific Committee to undertake the development of guidelines for landslide susceptibility and hazard and risk zoning for land use planning with the requirement that the committee produce guidelines that are acceptable to the international community. A first draft in this complex process was developed by the Scientific Committee using as a starting point a document prepared by the Australian Geomechanics Society. This draft was discussed and its applicability was tested within an international group of 40 experts (listed at the end of the preface) most of whom met for a workshop in Barcelona from September 18 to 20, 2006. This very fruitful workshop proved to be a forum for vigorous debate, and many helpful suggestions arose on how to improve the guidelines. Many of these suggestions have been included in the Commentary appended to the Guidelines. There were numerous additional suggestions (which were not included in the interest of balance and because of space restrictions) and a large number of formal corrections that were important to improve the quality of the guidelines. A set of accompanying papers have been also included in this special issue of Engineering Geology. These pa...

Several multivariate statistical analyses have been performed to identify the most influential geological and geomorphological parameters on shallow landsliding and to quantify their relative contribution. A data set was first prepared including more than 30 attributes of 230 failed and unfailed slopes. The performance of principal component analysis, t-test and one-way test, allowed a preliminary selection of the most significant variables, which were used as input variables for the discriminant analysis. The function obtained has classified successfully 88Ð5 per cent of the overall slope population and 95Ð6 per cent of the failed slopes. Slope gradient, watershed area and land-use appeared as the most powerful discriminant factors. A landslide susceptibility map, based on the scores of the discriminant function, has been prepared for Ensija range in the Eastern Pyrenees. An index of relative landslide density shows that the results of the map are consistent.