Search Results (8)

On 19 September 2021, a strombolian volcanic eruption began on the island of La Palma in the Canary Islands. This event resulted in the destruction of 73 km of roads, urban infrastructure, numerous houses, and agricultural crops, affecting approximately 7200 people and causing losses exceeding 1.2 billion euros. Around 12 km² were covered by aa and pahoehoe lava flows, which reached thicknesses of over 70 m. Following the end of the eruption, thermal, geological, and geotechnical site investigations were carried out for the reconstruction and territorial and urban planning, with the main objectives focused on opening roads through hot lava, constructing new urban settlements in areas covered by lava flows, and facilitating the agricultural recovery. The primary challenges to reconstruction included the very slow cooling rate of the lava, resulting in persistent high temperatures, exceeding 500 °C, its highly heterogeneous geotechnical properties with numerous cavities and lava caves, and the presence of toxic gases. Site investigations included geotechnical boreholes, seismic geophysics and ground-penetration radar, and temperature measurements of lava flows using drones and thermocouple devices inside boreholes. To estimate the cooling rates of the lava flows, two physical cooling models were developed based on thermal behavior and geological–geotechnical data. The results indicated that lava cooling durations in some areas exceed practical waiting times for commencing reconstruction. This led to the development of geological engineering solutions that permit road construction and urban and agricultural reconstruction to begin sooner than estimated by the cooling models. On the other hand, potential hazards arising from the eruption process have also been taken into account. Stability analyses of the 200 m high volcanic cone formed during the eruption indicate the possibility of failure in the event of heavy rain and consequently lahar hazards. The results of the investigations carried out and their applications to post-disaster reconstruction may be useful for other volcanic regions, contributing to minimizing risk to infrastructure and urban settlements. Full article

Risk Management Systems are a valuable tool for estimating the potential losses of natural events, assessing risk reduction strategies, and increasing the resilience of critical infrastructure. The paper discusses the development of SIGeR-RV, a tool for Risk Management of road networks exposed to multi-hazards developed in Chile. The tool was implemented on a web-based Geographic Information System platform. It is able to display hazard maps, calculate risk levels, prioritize mitigation strategies, estimate direct and indirect losses, and assess the social vulnerability of communities exposed to natural hazards. The article includes an application of SIGeR-RV in a road network exposed to the lahar flows of Villarrica volcano in the south of Chile. Full article

We forecast the impact that the lahars triggered on the summit of the Cotopaxi volcano in Ecuador would have upon the Hidroagoyán Dam should an 1877-type catastrophic eruption occur nowadays, with disastrous implications for the energy production of Ecuador. The Cotopaxi’ lahars have been simulated with the use of different computational models, yet none of them were so extended as to map their entire path to the dam. To fill this gap, we applied a version of the semi-empirical Cellular Automata LLUNPIY model to simulate primary and secondary lahars flowing from the summit of the Cotopaxi volcano until they reach the Hidroagoyán Dam in Baños. This version of LLUNPIY accounts for the triggering event by pyroclastic bombs and has already been validated by its successful simulation of the northbound 1877 cataclysmic lahars of the Cotopaxi volcano. The likely consequences of a similar disaster are discussed considering present territorial conditions. Computer simulations of natural hazards of this type represent a powerful tool that can be used when planning for the mitigation of environmental and social risks. Full article

Tailings flows resulting from tailings storage facility (TSF) failures can pose major risks to downstream populations, infrastructure and ecosystems, as evidenced by the 2019 Feijão disaster in Brazil. The development of predictive relationships between tailings flow volume and inundation area is a crucial step in risk assessment by enabling the delineation of hazard zones downstream of a TSF site. This study presents a first-order methodology to investigate downstream areas with the potential of being impacted by tailings flows by recalibrating LAHARZ, a Geographic Information System (GIS)-based computer program originally developed for the inundation area mapping of lahars. The updated model, LAHARZ-T, uses empirical equations to predict inundated valley planimetric and cross-sectional areas as a function of the tailings flow volume. A demonstration of a regional application of the LAHARZ-T model is completed for 46 TSFs across Canada. Although the variability in tailings properties and site characteristics cannot be perfectly incorporated or modelled, the LAHARZ-T model offers an efficient method for high-level, regional scale inundation mapping of several potential TSF failure scenarios. Full article

Cotopaxi is an active volcano in Ecuador, whose eruptions are characterized by producing destructive primary lahars which represent a major risk for the country. The hazard assessment related to such lahars relies largely on the knowledge of the latest event, which occurred on 26 June 1877, for either scenario definition or simulation calibration. A detailed (1:5000 scale) cartography of the deposits belonging to that eruption has been obtained in the proximal northern drainage of Cotopaxi. The cartography was performed through a combination of geological fieldwork, as well as the analysis and interpretation of high-definition imagery obtained by drone surveys combined with the Structure from Motion technology for image processing. Such imagery included red and green visible bands, and a near-infrared band, which allowed the obtention of NDVI imagery where the primary lahar deposits were identified and cartographed with support of fieldwork data. Both data sources are mutually complementary, and the final cartography would be impossible if any of them were not available. The results obtained represent a significant advance for the level of detail with respect to previous cartographic works. Moreover, they should allow an improved calibration of the new generation of numerical models that simulate lahar flow for hazard assessment at Cotopaxi. Full article

Natural hazards may temporarily or permanently interrupt the normal operation of rural road networks. The potential social, economic, environmental and physical impacts of natural events on rural road infrastructures empirically evidence the need to incorporate a sustainable risk approach to manage rural road networks exposed to natural hazards. Available risk management systems are applied to major networks emphasizing the physical risk of road infrastructure in terms of expected economic losses and travel time delays, without considering a systemic approach and other dimensions of risk, such as social vulnerability and the consequent socio-economic effects. The study proposes a sustainable risk management framework for rural roads that accounts for the social vulnerability of rural population, the physical vulnerability of rural roads and the environmental context in terms of natural hazards. The proposed framework is applicable to rural road networks exposed to major natural events that permanently or temporarily disrupt accessibility and mobility in the system. A case study is selected from a developing country, due to the socio-economic condition of the rural population and high vulnerability in the context of natural events. The proposed risk management framework is scaled at the network level rather than an element based analysis, or project level approach, considering the interdependencies between road links, the variability of road infrastructure types in the rural context, and the impacts on network accessibility and mobility due to natural events. The proposed framework is applied to a rural road network exposed to volcanic hazard, specifically lahar flows that are usually the most recurrent and disruptive process in terms of road infrastructure. Outcomes demonstrate that rural population present high social vulnerability levels, resulting in a slower recovery when exposed to the effects of infrastructure disruptions. Therefore, considering social vulnerability under a sustainable risk management approach depicts the sustainable role of rural road networks, which commonly are managed only under a physical vulnerability perspective. The proposed methodology will allow road agencies and municipalities to design sustainable mitigation and recovery strategies by incorporating dimensions such as social vulnerability, probability of failure of road links and their impacts on road accessibility and mobility due to natural hazards. Full article

Remote sensing data and methods are increasingly being embedded into assessments of volcanic processes and risk. This happens thanks to their capability to provide a spectrum of observation and measurement opportunities to accurately sense the dynamics, magnitude, frequency, and impacts of volcanic activity in the ultraviolet (UV), visible (VIS), infrared (IR), and microwave domains. Launched in mid-2018, the Special Issue “Remote Sensing of Volcanic Processes and Risk” of Remote Sensing gathers 19 research papers on the use of satellite, aerial, and ground-based remote sensing to detect thermal features and anomalies, investigate lava and pyroclastic flows, predict the flow path of lahars, measure gas emissions and plumes, and estimate ground deformation. The strong multi-disciplinary character of the approaches employed for volcano monitoring and the combination of a variety of sensor types, platforms, and methods that come out from the papers testify the current scientific and technology trends toward multi-data and multi-sensor monitoring solutions. The research advances presented in the published papers are achieved thanks to a wealth of data including but not limited to the following: thermal IR from satellite missions (e.g., MODIS, VIIRS, AVHRR, Landsat-8, Sentinel-2, ASTER, TET-1) and ground-based stations (e.g., FLIR cameras); digital elevation/surface models from airborne sensors (e.g., Light Detection And Ranging (LiDAR), or 3D laser scans) and satellite imagery (e.g., tri-stereo Pléiades, SPOT-6/7, PlanetScope); airborne hyperspectral surveys; geophysics (e.g., ground-penetrating radar, electromagnetic induction, magnetic survey); ground-based acoustic infrasound; ground-based scanning UV spectrometers; and ground-based and satellite Synthetic Aperture Radar (SAR) imaging (e.g., TerraSAR-X, Sentinel-1, Radarsat-2). Data processing approaches and methods include change detection, offset tracking, Interferometric SAR (InSAR), photogrammetry, hotspots and anomalies detection, neural networks, numerical modeling, inversion modeling, wavelet transforms, and image segmentation. Some authors also share codes for automated data analysis and demonstrate methods for post-processing standard products that are made available for end users, and which are expected to stimulate the research community to exploit them in other volcanological application contexts. The geographic breath is global, with case studies in Chile, Peru, Ecuador, Guatemala, Mexico, Hawai’i, Alaska, Kamchatka, Japan, Indonesia, Vanuatu, Réunion Island, Ethiopia, Canary Islands, Greece, Italy, and Iceland. The added value of the published research lies on the demonstration of the benefits that these remote sensing technologies have brought to knowledge of volcanoes that pose risk to local communities; back-analysis and critical revision of recent volcanic eruptions and unrest periods; and improvement of modeling and prediction methods. Therefore, this Special Issue provides not only a collection of forefront research in remote sensing applied to volcanology, but also a selection of case studies proving the societal impact that this scientific discipline can potentially generate on volcanic hazard and risk management. Full article

A good understanding of the frequency and magnitude of lahars is essential for the assessment of torrential hazards in volcanic terrains. In many instances, however, data on past events is scarce or incomplete, such that the evaluation of possible future risks and/or the planning of adequate countermeasures can only be done with rather limited certainty. In this paper, we present a multiidisciplinary approach based on botanical field evidence and the numerical modelling of a post-eruptive lahar that occurred in 2012 on the northern slope of the Pico de Orizaba volcano, Mexico, with the aim of reconstructing the magnitude of the event. To this end, we used the debris-flow module of the rapid mass movement simulation tool RAMMS on a highly resolved digital terrain model obtained with an unmanned aerial vehicle. The modelling was calibrated with scars found in 19 Pinus hartwegii trees that served as paleo stage indicators (PSI) of lahar magnitude in a sector of Jamapa Gorge. Using this combined assessment and calibration of RAMMS, we obtain a peak discharge of 78 m³ s⁻¹ for the 2012 lahar event which was likely triggered by torrential rainfall during hurricane “Ernesto”. Results also show that the deviation between the modelled lahar stage (depth) and the height of PSI in trees was up to ±0.43 m. We conclude that the combination of PSI and models can be successfully used on (subtropical) volcanoes to assess the frequency, and even more so to calibrate the magnitude of lahars. The added value of the approach is particularly obvious in catchments with very scarce or no hydrological data at all and could thus also be employed for the dating and modelling of older lahars. As such, the approach and the results obtained can be used directly to support disaster risk reduction strategies at Pico de Orizaba volcano, but also in other volcanic regions. Full article