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Farvacque M, Eckert N, Candia G, Bourrier F, Corona C, Toe D. Holistic rockfall risk assessment in high mountain areas affected by seismic activity: Application to the Uspallata valley, Central Andes, Chile. RISK ANALYSIS : AN OFFICIAL PUBLICATION OF THE SOCIETY FOR RISK ANALYSIS 2024; 44:1021-1045. [PMID: 37952939 DOI: 10.1111/risa.14239] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/14/2023]
Abstract
Over large regions exposed to natural disasters, cascading effects resulting from complex or concatenated natural processes may represent a large portion of total risk. Populated high-mountain environments are a major concern, and methods for large-scale quantitative risk analyses are urgently required to improve risk mitigation. This article presents a comprehensive quantitative rockfall risk assessment over a large archetypal valley of the Andean mountains, in Central Chile, which integrates a wide spectrum of elements at risk. Risk is expressed as an expected damage both in monetary terms and casualties, at different scales relevant for decision making. Notably, total rockfall risk is divided into its main drivers, which allows quantifying seismically induced rockfall risk. For this purpose, the local seismic hazard is quantified and the yield acceleration, that is, acceleration required to initiate rockfall, is determined at the regional scale. The probability of failure is thereafter derived in terms of annual frequency of rockfall initiation and integrated in the quantitative risk assessment (QRA) process. Our results show the significant role of seismic activity as the triggering mechanism of rockfalls, and highlight elements at risk that have a major contribution to the total risk. Eventually a sensitivity analysis is conducted to (i) assess the robustness of obtained risk estimates to the data and modeling choices and (ii) identify the most influential assumptions. Our approach evidences the feasibility of large-scale QRAs in sensitive environments and opens perspectives for refining QRAs in similar territories significantly affected by cascading effects and multihazards.
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Affiliation(s)
- Manon Farvacque
- Climate Change Impacts and Risks in the Anthropocene, Institute for Environmental Sciences, University of Geneva, Geneva, Switzerland
- Univ. Grenoble Alpes, INRAE, CNRS, IRD, Grenoble INP, IGE, Grenoble, France
| | - Nicolas Eckert
- Univ. Grenoble Alpes, INRAE, CNRS, IRD, Grenoble INP, IGE, Grenoble, France
| | - Gabriel Candia
- Facultad de Ingeniería, Universidad del Desarrollo, Las Condes, Santiago, Chile
- Research Center for Integrated Disaster Risk Management (CIGIDEN), ANID/FONDAP/15110017, Santiago, Chile
| | - Franck Bourrier
- Univ. Grenoble Alpes, INRAE, CNRS, IRD, Grenoble INP, IGE, Grenoble, France
| | - Christophe Corona
- Climate Change Impacts and Risks in the Anthropocene, Institute for Environmental Sciences, University of Geneva, Geneva, Switzerland
- Université Clermont Auvergne, CNRS, GEOLAB UMR, Clermont-Ferrand, France
| | - David Toe
- Univ. Grenoble Alpes, INRAE, CNRS, IRD, Grenoble INP, IGE, Grenoble, France
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Colavitto B, Allen S, Winocur D, Dussaillant A, Guillet S, Muñoz-Torrero Manchado A, Gorsic S, Stoffel M. A glacial lake outburst floods hazard assessment in the Patagonian Andes combining inventory data and case-studies. THE SCIENCE OF THE TOTAL ENVIRONMENT 2024; 916:169703. [PMID: 38228238 DOI: 10.1016/j.scitotenv.2023.169703] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/09/2023] [Revised: 12/11/2023] [Accepted: 12/24/2023] [Indexed: 01/18/2024]
Abstract
We present a glacial-related lake inventory for a region spanning 41.5° - 47° S in Patagonian Andes, where information on past glacier lake outburst floods (GLOF's) has hitherto remained significantly underreported. Analyzing remotely sensed images, we obtained data on 702 glacial-related lakes. Through detailed geomorphic assessments and manual supervision, we revised current inventories and added 35 GLOFs triggered from moraine/bedrock dammed lakes failures. The regional GLOF inventory presented contains information on 71 historical failures of moraine/bedrock dammed glacial lakes. From this database we analyzed outburst timing and managed to constrain 37 events occurrences within a period of 1 year. Around 40 % of them have occurred since the early 2000's, most of them originating from lakes probably formed as a delayed response to the glacial retreat imposed by the end of the Little Ice Age. On the other hand, we analyzed meteorological conditions for a sub-set of 10 events constrained within a 10-days period, finding a strong link between atmospheric rivers, cut-off lows impacting the southern Andes, and GLOFs. Only one case is likely to have been triggered by a Mw 4.9 earthquake. Based on topographic potential for avalanching, we estimated GLOF hazard potential, recognizing at least 3 subregions with high hazard, which moreover can be highly susceptible to climate conditions that regionally affect GLOF occurrence.
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Affiliation(s)
- B Colavitto
- University of Geneva, Institute for Environmental Sciences, Climatic Change Impacts and Risks in the Anthropocene, Switzerland; CONICET - Universidad de Buenos Aires, Instituto de Estudios Andinos "Don Pablo Groeber" (IDEAN), Buenos Aires, Argentina.
| | - S Allen
- University of Geneva, Institute for Environmental Sciences, Climatic Change Impacts and Risks in the Anthropocene, Switzerland
| | - D Winocur
- Universidad de Buenos Aires, Facultad de Ciencias Exactas y Naturales, Departamento de Ciencias Geológicas, Instituto de Estudios Andinos "Don Pablo Groeber" (UBA-CONICET), Buenos Aires, Argentina
| | - A Dussaillant
- Centro de Investigaciones en Ecosistemas de la Patagonia, Coyhaique, Chile; Universidad de Aysén, Coyhaique, Chile; UK Centre for Ecology & Hydrology, Wallingford, United Kingdom
| | - S Guillet
- University of Geneva, Institute for Environmental Sciences, Climatic Change Impacts and Risks in the Anthropocene, Switzerland
| | - A Muñoz-Torrero Manchado
- University of Geneva, Institute for Environmental Sciences, Climatic Change Impacts and Risks in the Anthropocene, Switzerland
| | - S Gorsic
- University of Geneva, Institute for Environmental Sciences, Climatic Change Impacts and Risks in the Anthropocene, Switzerland
| | - M Stoffel
- University of Geneva, Institute for Environmental Sciences, Climatic Change Impacts and Risks in the Anthropocene, Switzerland; Department of Earth Sciences, University of Geneva, Switzerland; Department F.-A. Forel for Environmental and Aquatic Sciences, University of Geneva, Switzerland
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The Use of UAV-Acquired Multiband Images for Detecting Rockfall-Induced Injuries at Tree Crown Level. FORESTS 2022. [DOI: 10.3390/f13071039] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
In this paper, we present an identification of rockfall-injured trees based on multiband images obtained by an unmanned aerial vehicle (UAV). A survey with a multispectral camera was performed on three rockfall sites with versatile tree species (Fagus sylvatica L., Larix decidua Mill., Pinus sylvestris L., Picea abies (L.) Karsten, and Abies alba Mill.) and with different characterizations of rockfalls and rockfall-induced injuries. At one site, rockfall injuries were induced in the same year as the survey. At the second site, they were induced one year after the initial injuries, and at the third site, they were induced six years after the first injuries. At one site, surveys were performed three years in a row. Multiband images were used to extract different vegetation indices (VIs) at the tree crown level and were further studied to see which VIs can identify the injured trees and how successfully. A total of 14 VIs were considered, including individual multispectral bands (green, red, red edge, and near-infrared) by using regression models to differentiate between the injured and uninjured groups for a single year and for three consecutive years. The same model was also used for VI differentiations among the recorded injury groups and size of the injuries. The identification of injured trees based on VIs was possible at the sites where rockfall injuries were induced at least one year before the UAV survey, and they could still be identifiable six years after the initial injuries. At the site where injuries were induced only four months before the UAV survey, the identification of injured trees was not possible. VIs that could explain the largest variability (R2 > 0.3) between injured and uninjured trees were: inverse ratio index (IRVI), green–red vegetation index (GRVI), normalized difference vegetation index (NDVI), normalized ratio index (NRVI), and ratio vegetation index (RVI). RVI was the most successful, explaining 40% of the variance at two sites. R2 values only increased by a few percentages (up to 10%) when the VIs of injured trees were observed over a period of three years and mostly did not change significantly, thus not indicating if the vitality of the trees increased or decreased. Differentiation among the injured groups did not show promising results, while, on the other hand, there was a strong correlation between the VI values (RVI) and the size of the injury according to the basal area of the trees (so-called injury index). Both in the case of broadleaves and conifers at two sites, the R2 achieved a value of 0.82. The presented results indicate that the UAV-acquired multiband images at the tree crown level can be used for surveying rockfall protection forests in order to monitor their vitality, which is crucial for maintaining the protective effect through time and space.
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Lu X. Mountain surface processes and regulation. Sci Rep 2021; 11:5296. [PMID: 33674779 PMCID: PMC7935956 DOI: 10.1038/s41598-021-84784-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
Mountains cover about a quarter of the world’s land surface, and directly support a significant proportion of the world’s population living within mountainous regions. Mountains provide water, timber and non-timber forest products, mineral resources, and many other food, fiber, and fuel products. Mountains also provide diverse ecosystems, in terms of both species and genetics, due to the topographic complexity in mountains increasing isolation and promoting speciation. Managing mountain regions for the sustainable delivery of critical goods and services requires an increasingly detailed understanding of mountain surface processes and regulation. The aim of this Guest Edited Collection is to provide a platform for interdisciplinary studies of mountain surface processes, and their responses to climate change and human activities.
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Affiliation(s)
- Xuyang Lu
- Institute of Mountain Hazards and Environment, Chinese Academy of Sciences, Chengdu, 610041, China.
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