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2023 | Buch

Advances in Natural Hazards and Volcanic Risks: Shaping a Sustainable Future

Proceedings of the 3rd International Workshop on Natural Hazards (NATHAZ’22), Terceira Island—Azores 2022

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This book comprises the selected proceedings of the 3rd International Workshop on Natural Hazards (NATHAZ’22), Angra do Heroísmo, Terceira Island, Azores, 2022. The book interests all researchers and practitioners in Earth Sciences, Volcanic Risks, Natural Hazards, Geoethics, Environmental Sciences and Engineering.

Terceira is a volcanic island with volcanic systems with caldera (Cinco Picos, Guilherme Moniz, Santa Bárbara and Pico Alto central volcanoes) and an active fissural zone defined by various alignments of small volcanic cones, lava domes and fault zones. The agricultural landscape, the natural and forest reserve, as well as the natural pools make the island a unique place to visit. The historic downtown of Angra do Heroísmo is a UNESCO world heritage, and several iconic buildings witness the island’s geodynamic history.

Natural hazards result from a threat of a naturally occurring event that will have a negative effect on humans. That damaging effect is often called natural disasters. Among the natural hazards and potential disasters to be considered are: earthquakes, volcanic eruptions, landslides, subsidence, floods, droughts and coastal erosion. In addition, anthropogenic hazards occur as a result of human interaction with the environment. They comprise technological risks due to exposure to hazardous substances in the environment.

Natural systems in different frameworks require a comprehensive understanding of climatology, geology, hydrology and volcanic data, processes and dynamics. Thus, it is important to perform hazard and risk assessment studies to accomplish hazard mitigation. In addition, it highlighted the role of variability and climate change in Earth systems. Furthermore, an accurate understanding of the natural systems and interactions with engineering, geodiversity and natural resources is vital to the entire socioeconomic sector.

This book is expected to offer an overview of natural hazards in model regions in Europe, America, Asia and the Atlantic islands. It gives new insights into the characterization, assessment, protection, and modelling of geological hazards, volcanic systems, urban areas, coastal zones and engineering approaches by international researchers and professionals. The scientific committee comprises lead geoscientists, natural hazards related practitioners, and academics worldwide.

The main topics include:
1. Multi-hazards and risks: sustainable society, disasters and geoethics
2. Natural hazards and assessment: rock falls, landslides, urban planning and management
3. Sustainable Earth systems: hazards and climate change
4. Terceira Island geology and geodiversity: meeting volcanological hazards in the Azores

Inhaltsverzeichnis

Frontmatter

Multi-hazards and Risks: Sustainable Society, Disasters and Geoethics

Frontmatter
Geoethics to Face Natural Risks by Improving Societal Resilience

Risks determined by natural phenomena cannot be cancelled entirely but can be reduced by minimizing their destructive effects. At present, scientists can predict, though with a certain degree of uncertainty, the onset and the evolution over time of most natural events. Scientific progress provides societies with advanced tools and methods to defend people, such as predictive models, monitoring instruments, early warning systems, and safe building standards. Nevertheless, the defence against natural risks should consider the ethical and social aspects involved in a risk scenario: this is fundamental to help the human community recover after a disaster and support science to identify possible solutions for an acceptable living with natural phenomena. Geoethics promotes the reflection on values that should guide human interaction with the territory and the associated and interlinked individual and collective responsibilities. Geoethics discusses issues and practices in natural risk management and fosters geoeducation and risk communication as a means to improve societal resilience.

Silvia Peppoloni
Multi-Hazard Risk Assessment at the Canary Islands

The term “multi-hazard” is a concept that is increasingly gaining ground in national and international disaster reduction policies. However, its implementation is still timid, and the initiatives that have been carried out are important but insufficient. Multi-hazard scenarios are still difficult to implement due to the complexity of the interactions between the different hazards, the lack of addressed research on this topic, and the uncertainty of their consequences at different spatial and temporal scales. Due to their intrinsic multi-hazard nature and their social, economic, and political context, volcanic islands are particularly vulnerable to these scenarios. These environments require adopting a multi-hazard perspective to design new multi-risk management programmes to reduce risk effectively. The case of the Canary Islands, an active volcanic archipelago that also suffers from multiple non-volcanic geohazards, is a clear example of such complex multi-hazard scenarios. With a worrying overpopulation and tourism that make this management difficult, and with emergency plans that do not consider this multi-hazard perspective, natural disasters may accentuate in the near future. This is also applicable to other volcanic islands in similar situations.

Marta López-Saavedra, Joan Martí
Risk-Informed Decision-Making on Volcanic Hazards

The safety of residents and tourists in volcanic regions is traditionally managed through an alert system with discrete levels ranging from no unrest to a major volcanic eruption. In recent years, substantial progress has been made in quantitative volcano risk modelling, which can generate estimates of eruption probability that can refine the discrete alert levels. The estimation of eruption probability is an important scientific interface between the volcanological community and public officials. It can help inform important safety decisions such as when to call a population evacuation or restrict tourist access, or conversely, when to allow people to return home or tourists to visit. The concept of risk-informed decision-making on volcanic hazards is explained and motivated by the need for all stakeholders to be more knowledgeable about the risk assessment process. Illustrations of the application of risk-informed decision-making are given, including the 2022 volcanic crises in Tonga and the Azores.

Gordon Woo
Geoethics: The Missing Piece in the Separation of Responsibility Between Volcanologists and Decision-Makers

In a volcanic crisis, authorized decision-makers must balance the social and economic costs of mitigating actions, such as evacuation, against the potential human losses if such actions are insufficient. In making their decisions, advice is needed from volcanologists on the eruption probability. Therefore, there should be a clear separation in the roles of volcanologists and decision-makers; the volcanologists should advise on the volcano hazard and alternative potential scenarios but refrain from involvement in making decisions. Currently, volcanologists are responsible for setting volcano alert levels. Given the small handful of distinct alert levels, there is inherent ambiguity and substantial uncertainty in the interpretation of individual levels. Furthermore, changing an alert level may automatically trigger actions by decision-makers. This would violate the principle of separation of responsibility and may result in unwelcome pressure being applied to volcanologists. Just as physicians can invoke medical ethics in resisting pressure to alter their advice, so volcanologists can invoke geoethics. Freedom to abide by their scientific beliefs is a basic tenet of geoethics.

Silvia Peppoloni, Gordon Woo, Joan Martí, Giuseppe Di Capua
Earthquakes, Volcanoes and God: Changing Perspectives on the Importance of Religion as an Important Influence in Cultural Responses

During the past thirty years, the authors have been engaged in researching the influence of religious belief on responses to earthquakes and volcanic eruptions. As late as the 1990s, the prevailing attitude within both the academic and disaster planning communities was that such responses, though important historically, had been progressively replaced since the Eighteenth-Century Enlightenment by notions of scientific contingency operating within largely secular frames of reference. Such attitudes where they remained were either those of a small minority in economically more advanced countries, or represented the last redoubts of superstition and irrationality in societies untouched by the forces of modernism. In this work, it is argued that academic and disaster planning perspectives have changed profoundly in recent years, and there is now recognition that, in many societies, not all of them economically less developed, there is a widespread religious framing of responses. Using examples from Christian, Judaic, Islamic, Hindu, Buddhist and Shinto traditions, the authors propose that religious believers and their resources (e.g. buildings, wealth and access to indigenous and foreign aid networks) may assist in the achievement of successful disaster risk reduction (DRR) policies.

David K. Chester, Angus M. Duncan
Towards a Multi-Hazard Assessment at Etna Volcano (Italy): The PANACEA Project

This work presents the first results of the PANACEA project regarding the assessment of different volcano-related hazards at Mt. Etna (lava and pyroclastic flows, tephra fallout and earthquakes) by exploiting data deriving from the volcano’s history with accurate physical–mathematical models. Volcano-related hazards are distributed differently on Etna—from the deserted summit area down to the densely populated flanks—but must be considered together for long-term territorial planning.

Raffaele Azzaro, Salvatore D’Amico, Tomaso Esposti Ongaro, Gaetana Ganci, Alexander Garcia, Simona Scollo, Marco Aliotta, Boris Behncke, Andrea Bevilacqua, Giuseppe Bilotta, Stefano Branca, Carmelo Cassisi, Mauro Coltelli, Paola Del Carlo, Mattia de’ Michieli Vitturi, Alessio Di Roberto, Luigi Lodato, Luigi Mereu, Michele Prestifilippo, Cristina Proietti, Laura Sandri, Tiziana Tuvè, Francesco Zuccarello, Annalisa Cappello
From Multi-Hazard to Multi-Risk at Mount Etna: Approaches and Strategies of the PANACEA Project

Managing multiple hazards simultaneously affecting a territory is a challenge for effective risk mitigation. This is particularly true on active volcanoes like Mt. Etna, characterized by effusive and explosive eruptions, often coupled with intense seismic activity. This work presents the PANACEA project’s approach to treating multi-hazards in terms of risk, which requires a common definition of the exposed elements and their vulnerability. Another aspect emerging from the recent and historical volcanic crises at Etna is the cascading effects and the problem of assessing their short-term interactions. A risk model is presented considering a set of sequences of hazardous events that may result from volcano unrest to possible impacts on some infrastructural elements. The project’s outcomes are intended to be a significant step toward a more comprehensive resilience to volcanic disasters, leading to a safer society.

Vera Pessina, Alexander Garcia, Fabrizio Meroni, Laura Sandri, Jacopo Selva, Raffaele Azzaro, Giuseppe Bilotta, Salvatore D’Amico, Mattia de’ Michieli Vitturi, Tomaso Esposti Ongaro, Gaetana Ganci, Luigi Mereu, Simona Scollo, Annalisa Cappello
The Role of the Individual in Successful Disaster Management in Pre-industrial Societies: The Cases of Southern Italy and the Azores

We contend that the leader was often the key actor in determining whether responses to disasters were successful in the pre-industrial societies of Southern Italy and the Azores (Portugal). We examine how leaders emerged and the ways in which they operated in the context of two similar, but in detail, very different societies shaped by a common Catholic ethos.

Angus Duncan, Rui Coutinho, David K. Chester, Nicolau Wallenstein, Stefano Branca, Alessandra Lotteri
Historical Volcanism as a Source of Knowledge to Assess the Vulnerability of Population Settlements in the Azores: Some Thoughts

There are records of more than two dozen volcanic eruptions since the settlement of the islands of the Archipelago of the Azores, some submarine, but many on land, subaerial. The recorded eruptions are centred on or close to São Miguel, Terceira, São Jorge, Pico and Faial islands. For the populations, eruptions are a source of concern and fear, transforming the landscape radically with the coverage of built elements and fields by ash deposits and other projected materials or lava flows, destroying their belongings and social environment. Nevertheless, over time, these new lands become sources of materials, new fertile lands, new geological and landscape elements with scientific and tourist potential and, consequently, urban reoccupation. This work starts with an analysis of the historical eruptions recorded in the Azores, types of activity and affected areas and seeks to assess the vulnerability of current populations to similar situations prospectively.

Fernando Pereira, Ana Oliveira, Ana Botelho, Paula Cabral, Luísa Magalhães, Tomás Medeiros
A Proposal for Systematisation of Vulnerability Elements and Parameters in Volcanic Risk Assessment

This work is part of the broader context of volcanic risk assessment, focusing on the identification, characterisation, and systematisation of the vulnerability elements and parameters to be considered for its determination. An extensive set of specialised bibliography was analysed to identify and characterise the various volcanic hazards (direct—lava flows, pyroclastic fall, pyroclastic flows and surges, lahars, and volcanic gases; and indirect—earthquakes, ground deformation, landslides, and tsunamis), and also the different elements of vulnerability (people, animals, all types of buildings, infrastructures, cultures, and all other economic activities). The global analysis allowed the identification and systematisation of vulnerability parameters to be built into a table in which general critical values are proposed, which can be used to determine vulnerabilities. Any analysis of this type must also include applying critical values specific to the area under study, considering each volcanic system’s specificity. This methodology was applied to Terceira Island to simulate two basaltic volcanic eruptions.

Ana Malheiro, João Luis Gaspar, Gabriela Queiróz, Teresa Ferreira, Paulo Amaral, Filipe Marques, Letícia Cunha

Natural Hazards and Assessment: Rock Falls, Landslides, Urban Planning and Management

Frontmatter
Specific Characteristics of Volcanic Materials in Landslides: A Geotechnical Outlook

Volcanism is related to active seismic tectonic areas. Numerous islands resulted from submarine volcanic eruptions. Different volcanic materials with specific characteristics (intrinsic parameters) are acted by seismic activity and extreme weather events (external parameters) interacting and generating landslide risks. Anthropic actions also contribute to the destabilization. Therefore, landslides are a destructive natural hazard. To mitigate or control the risk related to this type of hazard, it is necessary to understand the geotechnical properties of volcanic materials, which are very heterogeneous. Besides, there is less information about these geologic environments. On the other hand, geotechnicians with no experience in volcanic materials should not carry out this type of study without prior preparation. For this reason, a compilation of the generic properties of these materials, which contribute to the peculiarities of landslides in a volcanic environment, is made.

Celeste Jorge
A Decade of Monitoring and Research on the San Andrés Megalandslide on El Hierro, Canary Islands, Spain

Precise 3D dilatometric monitoring began on the San Andrés megalandslide detachment plane on El Hierro, Canary Islands, during the winter of 2013. It has been found that this presumably aborted giant landslide creeps progressively at rates of up to 0.5 mm a−1, with accelerations following periods of seismicity and extreme rainfall. In addition, a detailed multidisciplinary investigation of the landslide detachment plane has found that silica and cataclastic layers were produced during a pair of discrete slip events at 545–430 ka and 183–52 ka. Furthermore, slope stability analysis has suggested that creep may result from the deformation of sedimentary layers in the ocean, while destabilisation of the volcanic flank would require an earthquake with an intensity of at least VII. Finally, simple tsunami modelling based on conservative scenarios has shown that even a comparatively small event could have severe ramifications along the coasts of northwest Africa and southwest Europe.

Jan Blahůt, Jan Klimeš, Stavros Meletlidis, Jan Balek, Matt Rowberry, Ivo Baroň
Pico Volcano Flank Landslides and Hazard Implications: Preliminary Results

In the Pico volcano (Pico Island, Azores) flank, there is evidence of 8 major landslides that were the object of back analysis using the Generalized Limit Equilibrium method. The analyses yielded a close range of strength parameters for a safety factor equal to 1, with c′ = 10 kPa and average friction angle, ϕ′ = 40.1° (38.7–41.1°), for wet conditions, and similar values for the dry condition pseudo-static analysis, with c′ = 10 kPa and average ϕ′ = 40.2° (39.0–40.9°). The landslide’s shadow angle varied between 31.7 and 34.0° and showed no relation with the landslide’s scar elevation or planimetric area. Considering the numerous tension cracks at the upper part of the southern flank of the Pico volcano and the steep down-slope angle, there is the possibility of a large landslide developing and the debris travelling down to the S. Caetano cliff crest and village. These preliminary results suggest that this problem requires further studies to prevent or minimize the possible related hazards.

Fernando Marques
Improving Infrastructure Management for Rockfalls During Rainfall Events

Hazard refers to the probability of occurrence of a process (rockfall) with a given level of intensity or severity within a given time period and a specific area. For its evaluation, it is necessary to know the following aspects: where and when the processes occurred in the past, their intensity and magnitude, and the frequency of occurrence. The exposed elements can be people, goods, property, infrastructure, etc., which may suffer the consequences of rockfall directly or indirectly. Calculating the risk allows decisions and tailored solutions to be defined on protective measures and prioritises actions in the most at-risk sectors. Therefore, this study aims to describe the analysis of information on rainfall-induced rockfalls in Anaga, Tenerife (Canary Islands), in order to facilitate the improvement of road safety and operation in this geographical area by enabling the Road Maintenance and Conservation Services to mobilise the resources or means necessary to restore the roads to their previous state after the event/s or, where appropriate, to establish traffic limitations or restrictions to mobility.

Sergio Leyva, Noelia Cruz-Pérez, Jesica Rodríguez-Martín, Juan C. Santamarta
Detecting Anomalies in Volcanic Ashfall Forecast During Large Volcanic Eruptions: Sakurajima Taisho Eruption Case

In the form of fine ashes (i.e. ashfall), tephra affects vast, vulnerable areas with deadly consequences and long-term impacts. Moreover, both eruption scale and wind conditions exacerbate the catastrophe to a broader range. Accordingly, countries with volcanic risks have developed early warning systems to reduce the ashfall’s impact when a powerful explosive eruption occurs. Such systems utilize the prediction of expected eruption coupled with the numerical weather forecast to alert the people at risk and prepare the response activities. However, abrupt weather can influence the ashfall forecast to have inaccurate warnings. Here, we evaluate the quality of the forecast results as an early warning or an evacuation policy. Using the Sakurajima Taisho eruption as a case study, we simulate a volcanic ash dispersal process with two different wind data, predictive and historical data. This study found some alarming deviations (i.e. anomalies) in the ashfall forecast under specific weather conditions. The anomalies bring errors in defining the impact areas and unforeseen damages and losses. Furthermore, this study analyses the underlying pattern that causes a disturbance in the ashfall forecast and suggests improving the forecast results to enhance decision-making during crises.

Haris Rahadianto, Sudip Roy, Tetsuya Takemi, Masato Iguchi, Hirokazu Tatano
Rainfall and Its Infiltration Conditions for Landslide Occurred at Edge of Pyroclastic Flow Plateau in the Kyushu Island, Southwestern Japan

The torrential rains of July 2012 caused many landslides at the edge of the Aso pyroclastic flow plateau, consisting of the Aso-3 and the Aso-4 pyroclastic flow deposits in Kyushu Island, Japan. These landslides can be classified into two types: the caprock type, which occurred in Aso-4 areas, and the rainwater direct infiltration type, which occurred in Aso-3 areas. In both types, the landslide sliding surface is located in the lower pyroclastic fall layer of the pyroclastic flow deposit. The maximum hourly precipitation and effective precipitation with a half-life of 1.5 h control landslide occurrence and differ between landslide-prone and non-prone areas and between caprock and direct infiltration types. These parameters are larger in landslide-prone areas than in non-prone areas and are more significant in the caprock type than in the direct infiltration types. In a caprock type landslide, the effective stress in the pyroclastic fall layer estimated by theoretical calculations decreases with increased pore water pressure due to rainwater infiltration. Therefore, the landslide at the edge of the Aso pyroclastic flow plateau was caused by a decrease in effective stress in the pyroclastic fall layer.

Takehiro Ohta, Jumpei Yamashita, Yuki Sueda
Infrasonic Long-Range Observations at IS42: Study Cases of Grimsvötn (Iceland), Mt. Etna and Stromboli Volcanoes (Italy)

The collaborative research UNIFI–University of the Azores (IVAR) focused on the detection and characterization of events injecting energy into the atmosphere and allowed to analyze of the Grímsvötn volcano eruptive activity (Iceland) and Mt. Etna and Stromboli volcanoes (Italy) by several Stations (among which IS42) of the CTBTO’s International Monitoring System (IMS). Grímsvötn volcano, located under the Vatnajökull glacier, is the most active Icelandic volcano. The May 2011 explosive eruption broke the ice-covering and turned into sub-aerial, ejecting ash into the atmosphere and restricting flights across Northwestern Europe and the North Atlantic region. Mt. Etna, located in Sicily Island (Italy), is Europe’s largest and most active volcano. It is typically effusive with explosive episodes, and lava fountaining activity has recently produced high eruptive plumes causing an impact on local air traffic and nearby airports and cities. Finally, Stromboli volcano (Italy), located in one of the Aeolian Islands (Italy) with the same name, is one of the most active volcanoes on Earth, with sustained explosive activity and permanent degassing. A strong explosive event characterized by two distinct explosions occurred on July 3rd, 2019. In this study, we describe a multiple-detections analysis of (a) the May 2011 Grímsvötn eruption as observed at IS42 and other infrasound stations and its correlations with on-site observations; (b) the Mt. Etna eruptive activity of the May–September 2011 and the 2016 eruptions, as observed at IS42 and other stations, compared with near-source observations; and (c) the Stromboli July 3rd, 2019 event detections from IS42 and other IMS infrasound stations. We relate those results with events listed in the CTBTO Reviewed Event Bulletin (REB) to evaluate the potential of the IMS network in detecting and identifying sources of volcanic activity. In the framework of earth-based volcanic monitoring techniques, infrasound is a unique technology with the potential to detect explosive eruptions at great distances. Furthermore, simultaneous infrasound recording in near- and far-field represents a substantial improvement in the characterization of explosive sources.

Sandro Matos, Nicolau Wallenstein, Paola Campus, Maurizio Ripepe
Volcanic Island Drainage Divide Migration: Implications for Land Planning (Assomada Plateau, Santiago, Cape Verde)

Volcanic landscapes during island formation are due to lava flows and their accumulation processes. However, erosive processes dominate landscape reshaping during periods of volcanic inactivity, posing unique and crucial land-use planning challenges. In the North Atlantic Ocean, the Cape Verde archipelago is an excellent area for assessing the implications of erosive processes on the definition of land planning strategies. Accordingly, this study focuses on the extensive Assomada Plateau (municipality of Santa Catarina), located on Santiago Island. The research uses the geomorphological index Chi (χ) to evaluate directional erosional trends of the drainage divides and relates them with the present and future (master plan) of urban occupation. This study aims to define problematic areas where it is expected that the erosion from drainage divide migration will likely cause severe problems for human occupation. For the Assomada settlements, the master plan establishes the consolidation of the existing urban area and expansion of its periphery close to the southern plateau edge. Furthermore, asymmetric Chi value patterns reveal areas of intense erosion from the movement of the drainage divide to the North and West. Watercourses have already eroded the plateau base, with erosion branching off in three directions. As a result, several cliff edge buildings are at risk, and any further expansion in these areas is questionable.

Rui Fernandes, José Teixeira, Alberto Gomes, Martin Stokes
Does the Updating of Landslides Inventories Have a Relevant Impact on the Landslide Susceptibility Assessment?

Landslide inventories are essential for developing an accurate susceptibility assessment. However, the complete and systematic updating of these inventories is a time-consuming and challenging task. Therefore, we aimed to verify if the temporal updating of historical inventories improves the susceptibility models and if the size of the study area plays a relevant role in the decision to update or not landslide inventories. To answer these questions, the work was carried out in two study areas with different sizes but with a similar geomorphological context. The landslide susceptibility modelling, developed using the Information Value method, was performed for distinct types of landslides and using three landslide inventories: one with landslides that occurred before 2012; a second with landslides that occurred during the event of 2010; and a third with landslides that occurred up to 2019. The results indicate no improvement or only a residual enhancement in the susceptibility models’ predictive capacity, regardless of the type of landslide or the study area’s size.

Raquel Melo, Sérgio C. Oliveira, Ricardo A. C. Garcia, José Luís Zêzere
From Geological to Lithological Maps—Exploring Differential Erosion to Improve Lithological Information for Landslide Susceptibility Assessment

For landslide susceptibility assessment, lithology information is often extrapolated from official geological maps, which do not allow a direct spatial transformation into a detailed lithological map. To overcome this limitation, a study was made for the Grande da Pipa River basin, Portugal, to detail the existing geological maps, keeping the units’ age sequence but separating the main lithological types. In addition, it explored supplementary cartographic information (e.g., slope angle) to infer the boundaries of lithological units using differential erosion and associated morphological interpretation criteria. Finally, the lithological map produced was compared with the official geological map using sensitive analysis and different partitions of a historical landslide inventory. The results consistently record improved predictive capacity for landslide susceptibility if more detailed lithological maps are used instead of the commonly available geological maps.

Sérgio C. Oliveira, Raquel Melo, Fernando Marques, Rute Fonseca, Rita Pimenta, José Luís Zêzere
Road Network Exposure to Deep-Seated and Shallow Slides at the Basin-Scale (Grande da Pipa River Basin, Portugal)

Landslides are well-known for their destructive capacity; however, risk only exists if an interaction with people, activities, structures and infrastructures occurs. When landslides affect roads and potential human losses, both road damage and road disruption can cause significant economic losses. Therefore, in the framework of spatial planning, civil protection, emergency and risk management and the evaluation of road network landslide exposure is necessary. The primary goal of this work is to assess the present road network exposure to deep-seated and shallow slides at the Grande da Pipa River basin (North of Lisbon region, Portugal), an area naturally prone to geomorphological hazards. Our approach to assessing road network exposure is sustained by two different dataset inputs: (i) three landslide susceptibility maps and (ii) one road network map. The susceptibility to landslides, computed with the Information Value method and validated with success and prediction rate curves, as well as with the estimation of the area under the curves, was individually assessed for deep-seated rotational, shallow rotational and shallow translational slides. The road network exposure to each landslide type resulted from the intersection between the two top landslide susceptibility classes and the classified road network according to its rank, allowing the critical road sections to be identified. The road network is mainly exposed to deep-seated rotational slides. However, the other landslide types can also disrupt the road functionality and affect residents and economic activities.

Igor Branco, Sérgio C. Oliveira, Raquel Melo
The Functional Schematisation of the City as a Model for Anticipating Post-event Scenarios for Volcanic Hazards

Risk analysis requires the accurate characterisation of the hazardous events and their possible effects on the exposed elements. As demonstrated in recent events, volcanic activity may inflict several perturbations in urban functions, even compromising emergency-response actions. Thus, it is of the utmost interest to have holistic approaches that consider the city through its components for assembling feasible scenarios and performing mitigation strategies based on the system’s critical vulnerabilities. Failure Tree, Event Tree and Failure Mode and Event analysis are presented in this article as suitable approaches for conducting vulnerability-oriented research by using the village of San Pedro Tlalmimilulpan (México), in the context of the Popocatepetl volcano, as a case study. As demonstrated herein, these approaches facilitate the schematisation of the city based on the functions and infrastructures that, for a specific event scenario, are identified as critical for supporting sheltering and evacuation activities using such a traffic-light alert system. These analyses, supported by the existence of Risk Maps, reveal a series of proactive actions that would mitigate the adverse consequences of volcanic events. Furthermore, it is possible to find some highlights for designing a more efficient evacuation plan based on the most likely failures when analysing the singularities and location of a determinate village. The schematisation of urban functions in failure and event-based trees permitted identifying critical components of Tlalmimilulpan towards volcanic hazards, which may support the production of straightforward policies for risk mitigation and management in similar urban areas.

Rafael Ramírez Eudave, Tiago Miguel Ferreira
Multi-Hazard and Multi-vulnerability Analysis in Historical Urban Areas: Challenges and Opportunities

Natural hazards increasingly threaten urban areas, and single-risk analyses performed within different methodological frameworks are often not comparable with each other and pose some difficulties for decision-makers. This work highlights the challenges and opportunities of multi-hazard and multi-vulnerability assessment in historical urban areas with a multi-disciplinary approach. Two hazards, i.e., seismic and flood, are included in a multi-risk workflow based on common exposure, vulnerability, and risk metrics. The city center of Florence (Italy) is selected to demonstrate the methodology. The application suggests that estimating direct physical damages for earthquakes and floods requires a different characterisation of exposure and vulnerability parameters. The results show significant differences in the spatial distribution of multi-risk, mostly depending on the evolution of the constructive typologies from the Middle Ages to the XX century and the anthropic alteration of terrain morphology.

Chiara Arrighi, Marco Tanganelli, Vieri Cardinali, Maria Teresa Cristofaro, Antonino Maria Marra, Fabio Castelli, Mario De Stefano
Multi-scale Characterization of Flood Risk Components: A Case Study at the Municipal Level

Floods are complex processes that combine local and global factors, causing recurrent and significant human and material losses worldwide. The presented research consists of a multi-scale flood risk assessment process based on data sources collected at distinct scales, expressing hazard, exposure and physical vulnerability of buildings. Detailed Census-derived parameters are essential in representing exposure and vulnerability, while flood hazard is quantified from geomorphologically validated susceptibility maps combined with historical data that characterize events’ magnitude and frequency. The results allow a cross-scale analysis of risk, from the building to the municipality level, by identifying exposed populations, buildings, and physical vulnerability. The Lisbon Metropolitan Area is a highly contrasting territory regarding flood risk: some areas are susceptible to slow-onset floods in extensive floodplains but with low exposure, while densely urbanized areas are susceptible to flash floods in small watersheds. While the building level assessment is valuable for local civil protection and urban planning, municipal-level indices provide a comparable inter-municipal perspective of flood risk.

Pedro Pinto Santos, Susana Pereira, Tiago Miguel Ferreira, Maria Xofi, José Carlos Domingues, Carolina Pais, Sérgio Cruz Oliveira, Ricardo A. C. Garcia, Eusébio Reis, José Luís Zêzere, Paulo B. Lourenço

Sustainable Earth Systems, Hazards, and Climate Change

Frontmatter
Study, Definition and Application of General Alert and Alarm Criteria for Road Geotechnical Structures in the Operation and Maintenance Phase

The main purpose of this paper is to present the study, definition and application of general alert and alarm criteria to road geotechnical structures during the operation and maintenance phase. This work results from the need to apply global alert and alarm criteria to all the geotechnical structures of ASCENDI IGI. In the group of structures analysed, the following typologies of structures emerged: (i) Embankment slopes, (ii) Excavation slopes, (iii) Anchored walls, (iv) Reinforced Concrete walls, (v) Reinforced Earth walls, and (vi) Gabion walls. This document presents the monitoring and instrumentation methods implemented at ASCENDI. The general alert and alarm criteria were defined to support the interpretation of the installed instrumentation, particularly at the level of variations of displacements, deformations and loads. The definition of these criteria considers the type of structure (rigid or flexible), geometric characteristics, and material characteristics (geological and geotechnical). Since climate change is one of the greatest environmental threats of the twenty-first century, with profound consequences for various areas of society, this work intends to constitute an alternative approach to increase the resilience of geotechnical structures to natural hazards.

José Sousa, Pedro Varela, Sara Sanches, Adriana Neves, Alexandra Ferreira
The Effectiveness of Post-Wildfire Slope Stabilization Measures: A Case Study in Oliveira Do Hospital

The wildfires of the 15th of October 2017 consumed more than 190,000 hectares in central Portugal. Oliveira do Hospital stands out among the most battered regions, where 43,191 hectares of forest were lost. In the aftermath of this natural disaster, several interventions aiming at stabilizing unstable slopes were conducted in different regions of the council, namely along the road which connects Penalva de Alva to Oliveira do Hospital. These works consisted of temporary barriers along the upstream slope of the road. Due to three consecutive storms in 2019, several slope instability phenomena were recorded near the study area. Despite some minor surface landslides, almost all the instability events affected slopes that had not been intervened after the 2017 wildfires. The stabilized slopes showed a better response due to the non-degradation of the mechanical characteristics of the soils and the roots system. The conclusions are then discussed concerning the behaviour of volcanic soils and the potential effects of wildfires on slopes in regions having these materials.

Luis Araújo Santos, Paulo Coelho, António Correia
Methodologies for Mapping in Large Rock Excavations in Hazardous Geotechnical Contexts

This work intends to summarise the principles of geotechnical mapping as one of the fundamental elements in diverse applications, emphasising its use in underground works. This activity is generally integrated into the construction and extractive industry projects and is often the starting point for dimensioning and layout design. Developed and applied by geo-professionals with well-established and systematized techniques, with the support of new technologies and tools, while never leaving aside old and always reliable tools derived from geological mapping as the compass and geological hammer, geotechnical mapping has undergone several developments. As a result, it is increasingly recognised as part of major projects. Its application in underground works is a key part of their development, whether in the on-site investigations, design development, and excavations monitoring.

Cláudio Santa, Helder I. Chaminé, Isabel Fernandes
Dimension Stone Quarries Risk Assessment Estremoz Marbles

For centuries, dimension stone marble exploitation from the Estremoz Anticline, south Portugal, leads to a peculiar landscape consisting of hundreds of deep open-pit quarries. In the 80s of the last century, more than 180 quarries operate side-by-side simultaneously. The struggle for interesting outcrops, in addition to private property that legally characterises the mineral masses in Portugal, led to a situation where the quarries very close to each other developed into a well and independently. As the quarries reached greater depths, in several cases over 100 m, issues related to the slope stability became more evident and dangerous. It took an accident that caused 5 deaths due to a slope collapse that destroyed a municipal road for public entities to pay more attention to this issue. Within the scope of the Intervention Plan in Quarries Under Critical Situations (2019–2021), approved at the meeting of the Council of Ministers on February 7 (RCM 50/2019), the University of Évora carried out 34 slope stability studies in approximately 40 exploitation cavities for ornamental marble. This work summarises the identified main situations and the measures recommended for their mitigation.

Luís Lopes, Ruben Martins, António Pinho, Isabel Duarte, Paula Faria
Rock Cut-Slope Quarry Assessment (NW Portugal): A Preliminary Hazard Assessment

To safeguard the operations in rock quarrying, it is required to evaluate slope stability hazards systematically. This work investigates the slope stability in a rock quarry in NW Portugal and demonstrates the significance of geological, geotechnical, and geomechanical in situ investigations. The rock mass is a monzogranite, medium-grained, two-mica, essentially biotitic, predominantly fresh to slightly weathered (W1-2) to moderately weathered (W3), and highly fractured. The geomechanical classifications and geotechnical indexes RMR, GSI, SMR, SQR, and Q‐Slope allowed five geomechanical zones. Globally, the Southern part of the quarry has a fair to very good quality and the Northern part has a poor to fair quality. Three cut-slopes were studied in the Northern part of the quarry, which was considered unstable to partially stable. Several potential failures may occur, namely wedge slides and toppling failures. The application of the RHRSm2 system and the SQI permitted the classification of the cut-slopes with a high to very high-risk level and an urgent to very urgent intervention. RocFall and Swedge Rocscience software were used to model block fall in different areas and potential rock failures.

Luís Ramos, Ana Mendes, José Filinto Trigo, Fernando Pedro Figueiredo, Liliana Freitas, Maria José Afonso, Helder I. Chaminé
Monitoring System Implemented to Evaluate the Kinematics of an Instability Zone at Flores Island

Taking into account its geology, morphology and hydrology, the island of Flores (Azores archipelago) is susceptible to the occurrence of slow slope movements. These situations of instability have been more studied in the last 20 years. Following the studies, it has been found that these instability phenomena are increased when the weather conditions are more adverse, particularly regarding the duration and intensity of rainfall. The study presented in this document concerns two localities on Flores Island: Lajedo and Fajãzinha. The monitoring systems (vibrating wire and Casagrande piezometers, inclinometers, rain gauge station and total robotic station) were installed in two mass movements, and their results are presented. This work aims to determine alert and alarm thresholds based on the amount of precipitation and the water level variation in possible fault surfaces.

F. Marques, L. Moniz, P. Amaral, A. Malheiro, A. Santos
Geotechnics, Georesources and Natural Hazards: Impacts in Marine Technology and Oceanic Engineering

This essay addresses the importance of geotechnics and marine georesources in developing technologies. The study proposes a coastal and marine geoengineering approach that focuses on five domains (5G’s): georesources, geology, geotechnics, geomechanics and geotechnologies. These domains are considered in several engineering projects related to coastal, hydraulic, marine, and maritime applications. The reality of a world in rapid, continuous evolution has put into perspective a multidisciplinary approach combining different practices and coastal strategies. That is the main driving force that should be considered when dealing with geoengineering projects in general. Moreover, geological resources and the potential exploitation of mineral and rock raw materials boost innovative techniques and upscaling geo-robotic systems. Finally, the essay unravels new trends in challenging and extreme environments and natural hazards, highlighting emerging fields such as deep-sea mining, geo-exploration, offshore, coastal, harbour and marine geotechnics.

Ana Pires, Helder I. Chaminé
Analysis of Morphological Changes at Aveiro Coast (NW Portugal) Between 2012 and 2018

Repetitive data collection is imperative regarding accurate coastal monitoring and appropriate coastal management strategies design. This study analyses high-resolution topo-bathymetric data gathered at Aveiro coast (NW Portugal) between 2012 and 2018. Using Geographic Information System techniques, the beach response and the sediment budget evolution are assessed for both emerged and submerged areas, evidencing places where coastal erosion and accretion occur. The methodology includes creating digital terrain models to compute the volume differences for this period and estimate the sediment budgets. The results are discussed in anthropic activities such as dredging and artificial nourishment operations in this littoral region. An overall erosion tendency is observed on the emerged beach, which seems to be compensated with beach nourishment interventions. However, the submerged beach also reveals a general erosive tendency at the inlet, and, among other factors, it seems to be affected by dredging operations and the southwest extension of the north pier.

Tiago Abreu, Paulo A. Silva, Paulo Baptista, Cristina Bernardes, Sandra Fernández-Fernández, Caroline Ferreira, Ángela Fontán-Bouzas
Equilibrium Beach Profile: La Garrofera Beach Case Study

The constructive and destructive forces acting on a beach profile influence the beach cross-shore profile. For an equilibrium profile, the response to wave forcing should result in a constant shape depending on incident waves or sediment characteristics. A panoply of formulations can be found to represent this equilibrium beach profile in both tidal and non-tidal beaches and the presence or absence of longshore bars. The main objective of this work is to verify if some easy-to-apply and straightforward models can provide an excellent fit for the cross-shore profile of La Garrofera beach, located in the Mediterranean Sea at Valencia (Spain). Beach characterization is made in terms of its morphology, nature of the soil and sediment characteristics, and wave regime. Three models are tested against bathymetric field data, showing reasonable predictions of the measured beach cross-shore profile. Furthermore, they all correctly predict the expected concave-up form characteristically found on wave-dominated beaches.

Tiago Abreu, Maria de Fátima Silva, Luís Vasconcelos, Sheila Torres-Toran
Numerical Validation of a Newly Developed River Morphological Prediction Software

UMHYSER-1D (Unsteady Model for the HYdraulics of SEdiments in Rivers 1D) is a one-dimensional hydromorphodynamic software that computes water surface profiles in a single river or multiriver network for sub/supercritical flow regimes taking into account cohesive or non-cohesive sediment transport. UMHYSER-1D simulates steady and unsteady flows, with or without sediment transport. This paper presents numerical validation of UMHYSER-1D. By using a published study case of the US Bureau of Reclamation, the results of UMHYSER-1D are compared to those of the USBR software, SRH-1D. This study case is used to validate numerically UMHYSER-1D under unsteady flow and sediment transport conditions in a long reach of the Rio Grande River, more than 100 km long. UMHYSER-1D gives almost the same results as SRH-1D. The maximum differences observed at the two cross-sections are very acceptable. After its laboratory validation in a previous paper, the present work confirms that UMHYSER-1D is ready to be used as a numerical laboratory for fluvial hydraulics and/or a powerful tool to solve real engineering problems. UMHYSER-1D can be used for river morphological changes due to natural or human influences.

Tew-Fik Mahdi
Hydraulic Analysis of the Suitable Construction Solutions in the Middle Tiber River

The hydraulic safety of the historic centre of Rome is guaranteed by preventing flooding events of the Tiber River by the embankment walls called “Muraglioni”. For this reason, it is necessary to maintain the flood attenuation capacity ensured by the flooding of the floodplain areas upstream of the city. The urban developments of these areas are sustainable only by hydraulics engineering infrastructures aimed at controlling the flood in the floodplain areas in case of 100-year and 200-year return time meteoric and hydraulic extreme events. This work presents the engineering solutions and the results of the hydraulics analysis carried out on making compatible road infrastructures and flood protection infrastructures in the territory, such as river embankments and detention basins. The Tiber River has been studied to respect this target, setting up a one-dimensional numerical model using HEC-RAS and a two-dimensional model using SMS and BAS.E.MENT software. The numerical simulations of floods have been carried out with a 200-year return time in the several phases of construction of the infrastructures in the area. The analysis identified the most suitable design choices, saving the neighbouring Rome metropolitan area from increasing hydraulic risks.

Giuseppe Sappa, Giuseppe Mellace

Terceira Island Geology and Geodiversity: Meeting Volcanological Hazards

Frontmatter
Volcanic Geology of Terceira Island, Azores: A Field Guide to Geodiversity

Terceira in the Azores archipelago is one of the most geologically diverse islands of the Atlantic Ocean and its geodiversity is due to the close relationship between tectonics and magmatism. This strong interaction is translated by the presence of large central volcanoes with calderas and a WNW-ESE-trending fissure zone that crosses them. The active tectonics of Terceira is well expressed by the Lajes Graben, which was the source of some of the more destructive earthquakes in the Azores. Moreover, the bimodal geochemistry of Terceira is recorded, on the one hand, by the numerous basaltic eruptions that punctuate the island and, on the other hand, by the less frequent but large trachytic (peralkaline) explosive eruptions of the central volcanoes. Among the latter, ignimbrite-forming eruptions are the most hazardous phenomena, and in case of such a future eruption the island would suffer catastrophic consequences. Historical eruptions have occurred on land (1761) and at sea offshore Terceira (1867 and 1998–2001), but with no record of casualties. This chapter highlights the diversity of geological structures found on Terceira Island, including tectonic faults, volcanoes and their products, volcanic caves, and geothermal areas, with attention to the associated volcanic hazards.

Adriano Pimentel
Volcanological Features of Terceira Island (Azores): A Field Approach Around Hazards

Terceira Island (400 km2 area and the second most inhabited of the archipelago) comprises four polygenetic volcanoes with caldera (Cinco Picos, Guilherme Moniz, Santa Bárbara and Pico Alto central volcanoes) and an area of active fissural basaltic volcanism, split into two main sectors of the island, on its central and southeast zones. Impressive siliceous effusive volcanism products mark the island's geology and landscape as numerous domes and coulees: a total of about 160 eruptive centres of this type can be observed on the island, especially on the Santa Bárbara and Pico Alto volcanoes, with a clear morphological signature. Historical volcanism dates back to the eighteenth century, with land eruptions in 1761 (the “Mistérios Negros” and the “Mistério Novo” areas) and submarine eruptions in 1867 and 1998–2001, the latter in the Serreta submarine ridge. This work outlines a field trip on Terceira Island, emphasising its geological characteristics and geohazards.

João Carlos Nunes
Backmatter
Metadaten
Titel
Advances in Natural Hazards and Volcanic Risks: Shaping a Sustainable Future
herausgegeben von
Ana Malheiro
Francisco Fernandes
Helder I. Chaminé
Copyright-Jahr
2023
Electronic ISBN
978-3-031-25042-2
Print ISBN
978-3-031-25041-5
DOI
https://doi.org/10.1007/978-3-031-25042-2