Preface "Progress in landslide hazard and risk evaluation"

Abstract

Federal Institute for Geosciences and Natural Resources, Hanover, GermanyCorrespondence to: P. Reichenbach (paola.reichenbach@irpi.cnr.it)The special issue of Natural Hazards and Earth SystemSciences entitled “Progress in landslide hazard and risk eval-uation” contains 9 out of more than 30 oral and poster con-tributions originally presented in the “NH3.11 Landslide haz-ard and risk assessment, and landslide management” sessionheld at the General Assembly of the European GeosciencesUnion, in Vienna (Austria), on 22–27 April 2012.The session was aimed at comparing qualitative or quanti-tative landslide hazard and risk estimates in different physio-graphic and geographical settings for different kinds of pro-cesses affecting the environment at different spatial scales.Presentations focusing on the adoption and integration ofdifferent modeling approaches for quantitative assessmentswere welcomed, and papers providing information on thequality, reliability and limitations of process-oriented or sta-tistical models were encouraged.The meeting proved to be a valuable opportunity to discussand compare methods, techniques and tools for the recog-nition, evaluation and mitigation of landslide hazards andthe related risks. In particular, the quality, the reliability andthe limitation of models, input variables and output mapshave been discussed for presented case studies at differentgeographical scales and in different physiographic environ-ments. This is important information for filling the gap be-tween academic research and application of the results inenvironmental planning and management. The special issuecontains the following selected papers presented and dis-cussed at the session.Voumard et al. (2013) have calculated risk along roadsusing a dynamic traffic approach that simulates the durationof the presence of vehicles inside hazardous areas during agiven time interval. The risk is analyzed along three roadsections threatened by different natural hazards (active land-slide, debris flows and dolines) along a mountain road: Aigle– Col du Pillon (western Switzerland). Two different scenar-ios were simulated: (1) a road without obstacles and (2) aroad regulated by traffic lights. Results of the dynamic riskassessment were compared with the static methodology thatconsiders an average number of vehicles per time unit and aconstant vehicle speed. The main advantage of the dynamicapproach is a better representation of the real traffic regardingthe interaction between different vehicles of different types(cars, trucks, coaches). The dynamic approach with a micro-scopic traffic simulator was well designed to analyze the riskon relatively short road sections (up to a few kilometers) indetail. At the regional scale, the risk estimations would beaveraged over the entire network (with large parts at no risk),and differences between static and dynamic risks may not beso pronounced. Thus, the interest of this method is to analyzehotspots, i.e., strongly hazardous short road sections, and tosee for example how the location of traffic lights can increaseor reduce the risk.Catani et al. (2013) have performed different tests to un-derstand how model tuning and model parameters can af-fect landslide susceptibility mapping. In the paper, the au-thors have adopted the random forest (RF) technique to pro-duce an ensemble of landslide susceptibility maps for a setof different models, input data types and observation scales.The RF model was initially applied using the complete set ofinput variables, then an iterative process was implemented,and progressively smaller subsets of the parameter spacewere considered to estimate the relative importance of sin-gle input parameters and to select the optimal configurationof the classification model. The main results are that (i) theoptimal number of parameters varies with scale and resolu-tion, (ii) the importance of each conditioning variable is in-fluenced by the model settings and the available data, andPublished by Copernicus Publications on behalf of the European Geosciences Union.