BEGIN:VCALENDAR VERSION:2.0 PRODID:-//pretalx//talks.staging.osgeo.org//foss4g-2022//speaker//V9X98A BEGIN:VTIMEZONE TZID:CET BEGIN:STANDARD DTSTART:20001029T040000 RRULE:FREQ=YEARLY;BYDAY=-1SU;BYMONTH=10 TZNAME:CET TZOFFSETFROM:+0200 TZOFFSETTO:+0100 END:STANDARD BEGIN:DAYLIGHT DTSTART:20000326T030000 RRULE:FREQ=YEARLY;BYDAY=-1SU;BYMONTH=3 TZNAME:CEST TZOFFSETFROM:+0100 TZOFFSETTO:+0200 END:DAYLIGHT END:VTIMEZONE BEGIN:VEVENT UID:pretalx-foss4g-2022-9SNJEH@talks.staging.osgeo.org DTSTART;TZID=CET:20220825T174500 DTEND;TZID=CET:20220825T181500 DESCRIPTION:Rockfall risk analysis and mitigation activities are key points in land management in mountain areas and along coastal cliffs\, aimed at the protection of population\, structures\, infrastructures and involved e conomic activities such as viability\, industry and tourism. \nRockfall is a complex landslide phenomenon\, widespread over large areas and characte rised by high variability. As a function of the amount of available data t o describe such variability\, the risk analysis can be carried out at diff erent levels of detail\, i.e. at different reference scales\, each one cha racterised by specific objectives\, procedures\, and input data (Fell et a l\, 2008).\nAt the detailed scale (> 1: 5000)\, in order to design risk mi tigation works\, it is necessary to analyse localized rockfall phenomena t hrough specific methodologies requiring a careful identification of danger scenarios\, a statistical description of the parameters\, and sophisticat ed probabilistic calculation tools.\nAt the medium-large scale (1: 5000 - 1: 25000)\, on the contrary\, due to the difficulty in finding detailed in formation over larger slope portions\, it is possible to analyse widesprea d instability sources based on simplified mechanical considerations and se veral spatial approximations. Such large scale analyses can be used as a m anagement tool for territorial planning and can be easily implemented in G IS software.\nThis work presents a medium-large scale Rockfall Quantitativ e Risk Assessment procedure fully developed within the QGIS environment. T he procedure is based on the IMIRILAND methodology (Castelli and Scavia\, 2008)\, which allows to obtain risk maps through integrated and consequent ial phases and simple raster calculations. The main steps of IMIRILAND met hodology are:\n• hazard analysis\, aimed at defining\, for a given rockf all scenario\, the potentially involved area\, the intensity of the damagi ng phenomenon and the temporal probability of occurrence\;\n• identifica tion of the elements at risk and definition of their value and their expos ure with reference to physical\, social\, environmental and economic cons iderations\;\n• analysis of the vulnerability of the elements at risk\, i.e. the degree of loss of the element as a consequence of the impact with the falling block\;\n• calculation of the risk\, combining the hazard w ith value\, exposure and vulnerability of the elements at risk.\nThe IMIRI LAND QRA procedure was applied to the mountain site of Sorba Valley (VC)\, North-Western Alps. The site involves an area of about 10 km2 with altitu des ranging from 750 m up to 2035 m a.s.l. The site is prone to rockfall e vents\, which historically involved some hamlets and some sections of the valley main road. However\, very little information on such events is avai lable\, and no indication can be obtained in terms of rockfall recurrence and involved volumes. Due to this\, it was not possible to take into accou nt temporal aspects and relative (spatial) risk maps were produced in this work.\nAll the analysis was carried out using open data available as web services and datasets from the Regione Piemonte GeoPortal:\n• DTM with 5 m x 5 m raster resolution – GeoPortale Piemonte\;\n• Orthophoto AGEA 2018 – GeoPortale Piemonte\;\n• Piemonte Land Cover BDTRE (Base Dati T erritoriale di Riferimento degli Enti) – GeoPortale Piemonte\;\n• vehi cular mobility TGM (Traffico Giornaliero Medio) – GeoPortale Piemonte.\n Three rockfall design scenarios were identified regarding homogeneous rock fall source areas associated with different design block volumes. Each sce nario included more than 3600 source points\, extracted through the analys is of the DTM (slope and aspect) and the observation of the orthophoto for the identification of rocky outcrop zones. For each scenario\, a quick es timation of a time-independent hazard was performed using the QGIS QPROTO plugin (Castelli et al\, 2021). The plugin is based on the Cone Method (Ja boyedoff and Labiouse\, 2011) and runs a visibility analysis through the r .viewshed GRASS GIS module\, combined with simplified topographic\, geomor phological and mechanical considerations. The result of the analysis is a series of raster maps with the distribution of computed values of velocity \, energy\, and relative spatial hazard. \nThe following step of the IMIRI LAND procedure is the analysis of the damage\, based on the collection of information on the exposed elements. To this aim:\n• the elements at ris k were classified according to various Land Cover categories from BDTRE\, associated with relative hierarchical values. Physical and social values w ere taken into account for each element. Physical value is mainly linked w ith the type of element and with the reconstruction costs while social val ue is linked to the presence of persons and the social utility of the asse t\;\n• the physical exposure of the elements at risk was defined for eac h hazard scenario with reference to the computed runout area. The social e xposure was defined taking into account the time spent by people inside bu ildings or on the roads. \n• the physical vulnerability of the elements at risk was defined on the basis of the intensity of the phenomenon in ter ms of rockfall energy and the type of element. The social vulnerability is the same as the physical one inside buildings and is 100% outside buildin gs. \nPhysical and social damage maps were then obtained for each hazard s cenario through the product of the value\, the exposure and the vulnerabil ity of the elements located in the involved area. Due to the lack of infor mation on the temporal probability of occurrence of the scenarios\, damage maps correspond to relative\, time-independent\, risk maps. \nThe results show that the highest risk is concentrated in the inhabited areas and som e portions of the valley road\, according to the few historical informatio n available on the site. \nThe QPROTO plugin is available at the GIT repos itory of FAUNALIA (gitlab.com/faunalia/QPROTO) and can be easily used by p rofessionals\, public administrators\, managers of roads\, railways or inf rastructures for land planning purposes or for preliminary analyses aimed at defining the most critical zone of a wide area\, where resources and mo re in-depth analyses can be focused for mitigation purposes. DTSTAMP:20260405T122052Z LOCATION:Room Onice SUMMARY:Rockfall Quantitative Risk Assessment at a medium-large scale based on FOSS4G tools. An example of applications in the North-Western Alps - M arta Castelli URL:https://talks.staging.osgeo.org/foss4g-2022/talk/9SNJEH/ END:VEVENT END:VCALENDAR