Marina Bisson

Coastal regions of the Mediterranean basin are increasingly experiencing the impacts of climate change. Among these, sea-level rise (SLR), combined with land subsidence and storm surges, represents a major hazard for coastal environments, affecting urban areas, transport systems, ports, and other critical infrastructures. Low-lying coastal zones are particularly vulnerable to accelerating SLR, which enhances the exposure of coastal communities to flooding, shoreline retreat, and erosion. Rising sea level can also amplify the impacts of extreme events such as storm surges and tsunami. In this context, the Northern Adriatic Sea represents one of the most vulnerable sectors of the Mediterranean due to the combined effects of global SLR and significant vertical land motion (VLM), with prevailing subsidence. This study investigates future relative sea-level rise (RSLR) scenarios along the Emilia-Romagna coast (Italy) up to 2150, with particular attention to the role of differential subsidence and its implications for coastal infrastructures. The analysis integrates multiple datasets: (i) InSAR data from the Copernicus European Ground Motion Service and GNSS geodetic data from local networks to quantify the subsidence rates in the investigated area; (ii) Airborne LiDAR data provided by the Italian Ministry of the Environment to generate high-resolution digital elevation models (DEMs) for projecting potential flooding extents; and (iii) SLR projections from the IPCC AR6 under different SSP climate scenarios for the Mediterranean basin, revised for current rates of VLM. Finally, we provide a classification of the different areas according to their exposure and risks to the combined effects of VLM, SLR and storm surges, producing heterogeneous patterns of coastal vulnerability and identifying critical coastal infrastructures at risk of inundation. Our findings provide new insights into the combined effects of climate-driven SLR and land subsidence in the Northern Adriatic, support the development of adaptation strategies and coastal risk mitigation measures also for other vulnerable Mediterranean coastal systems.

During the years 2021-2022 Vulcano island was affected by a volcanic crisis characterized by a remarkable increase in fumarolic activity, intensified seismicity and ground deformations. With the aim of reproducing with high detail the island surface after this crisis, an Airborne Lidar survey was carried out on 4 ^th August 2023. More than 200 × 10 ⁶ 3D Lidar points were processed to create a new Digital Surface Model at a very high spatial resolution (50 cm). This model reproduces the elevation surface of all natural and anthropic elements constituting the island. The model was validated through a set of Ground Control Points and a vertical accuracy of 8 cm was obtained. This level of accuracy, combined with the spatial resolution of 50 cm, makes the model particularly suitable for detailed geomorphological investigations. In addition, associated with the derived coastline, it provides the most up-to-date and accurate 3D topography for the assessment of natural hazards, such as changes in the volcanic activity state, earthquakes and mass movements triggered by extreme rainfalls.

Colli Albani Hills, a volcanic complex located 20 km SE of Roma (Italy), represents a long-dormant caldera system and its last eruption is dated back ~ 20 ky. It is subjected to seismic swarms, gaseous emissions and ground deformations. The whole volcanic complex is affected by landslides of different typologies and in the past the most frequent were debris flows. In this study, for the first time, the debris flows susceptibility of the complex is mapped through a heuristic approach that combines parameters recognized in literature as the main predisposing factors to slope instability. Such parameters are morphometry elements, lithology and land cover. The resulting map, validated through historical landslides, classifies the entire complex according to five degrees of susceptibility, identifying Tuscolano-Artemisio caldera edge, Mt. Faete, and steep slopes of Nemi and Albano lakes at high and very high susceptibility. The instability of the entire complex is further investigated measuring the ground deformations observed by using InSAR data in the period 2016–2023. InSAR results, validated through GNSS data, show the overall stability of the complex, except a few areas. In detail, an ongoing uplift of about 1.5 mm/yr is recorded in Genzano di Roma municipality. The InSAR results combined with the debris flows susceptibility map and historical landslides highlight the steep slopes of Albano and Nemi lakes and Giulianello locality, outside the caldera, as the areas potentially most predisposed to trigger debris flows as classified at very high susceptibility and affected by both ground deformations and historical debris flows.

Digital surface models reproduce the 3D topography of a territory at different spatial resolutions depending on the acquisition technique of source data. In active and densely populated volcanic areas, updated digital topographies are fundamental for mapping and quantifying the morphological changes generated by the eruptive events and play a key role in modelling volcanic phenomena and related hazards. This work presents the high-resolution Digital Surface Model of Stromboli Island, Italy, updated to 4^th August 2023. The model, obtained by elaborating more than 109 × 10⁶ Airborne Lidar points (x,y,z), reconstructs the volcano’s surface through an elevation matrix at a spatial resolution of 50 cm, reproducing both natural and anthropic elements. The model has been validated by using Ground Control Points and the vertical accuracy results in 8 cm. Nowadays, this model represents the most updated and accurate digital 3D topography of the entire island and, for this reason, can be considered a relevant data not only for multi-temporal morphological and volcanological analyses but also for hazard assessment studies.

Lahars represent some of the most dangerous phenomena in volcanic areas for their destructive power, causing dramatic changes in the landscape with no premonitory signs and impacting on population and infrastructures. In this regard, the Campanian Plain turns out to be very prone to the development of these phenomena, since the slopes of the Somma-Vesuvius and Campi Flegrei volcanoes, as well as the nearby Apennine reliefs, are mantled by pyroclastic deposits that can be easily remobilized, especially after intense and/or prolonged rainfall. Our recent studies focus on the analysis of the pyroclastic fall and flow deposits, and of the syn- and post-eruptive lahar deposits related to two sub-Plinian eruptions of Vesuvius, 472 CE (Pollena) and 1631. Historical and field data from the existing literature and from hundreds of outcrops were collected and organized into a database. Stratigraphic, sedimentological, and archaeological analyses were carried out, in addition to rock magnetic investigations and impact parameter estimations. The field data analyses show that in both eruptions the dispersal area of the primary pyroclastic deposits is wider than previously known. Such distribution of the deposits directly affects the one of the lahar deposits, even because a significant remobilization took place during and after the studied eruptions, involving the distal phreatomagmatic ash. From these analyses, it was possible to constrain the timing of the deposition, and to estimate the thicknesses, velocities and dynamic pressures (impact parameters) of the lahars. A new shallow layer model based on depth-averaged variables, named IMEX-SfloW2D, was developed for the simulation of lahar dynamics. A thorough sensitivity analysis was carried out to identify the critical processes (erosion and deposition) and parameters (numerical and physical) controlling lahar runout, using both synthetic and real cases topographies. Effects of erosion and deposition were investigated by comparing field data with the output of simulations including vs. excluding these processes. By comparing observed and simulated flow thickness and area covered by the flows, and their evolution over time, it can be shown that the inclusion of erosion and deposition is important to properly simulate the impact parameters of lahars, particularly on uneven terrain. Lastly, a novel workflow for Probabilistic Volcanic Hazard Assessment (PVHA) for lahars was developed and applied to the Vesuvius case study. Such a workflow explores the effect of uncertainty of the flow initial conditions on the impact parameters of lahars on the target area, by sampling coherent sets of values for the input model parameters and running thousand simulations. The simulation outputs were processed to produce hazard curves, hazard maps, and probability maps for the maximum flow thickness, and hazard surface and probability maps for joint thresholds in flow thickness and dynamic pressure. It is believed that the latter hazard products represent a novel product in PVHA for lahars around Vesuvius volcano and can be applied worldwide. The multidisciplinary approach adopted in this work shows how it is crucial to assess the impact of lahars in densely populated areas, even at distances of several to tens of km from active volcanoes like Vesuvius.

In this study we present a novel general methodology for probabilistic volcanic hazard assessment (PVHA) for lahars. We apply the methodology to perform a probabilistic assessment in the Campanian Plain (southern Italy), focusing on syn-eruptive lahars from a reference size eruption from Somma–Vesuvius. We take advantage of new field data relative to volcaniclastic flow deposits in the target region (Di Vito et al., 2024b) and recent improvements in modelling lahars (de' Michieli Vitturi et al., 2024). The former allowed defining proper probability density functions for the parameters related to the flow initial conditions, and the latter allowed computationally faster model runs. In this way, we are able to explore the effects of uncertainty in the initial flow conditions on the invasion of lahars in the target area by sampling coherent sets of values for the input model parameters and performing a large number of simulations. We also account for the uncertainty in the position of lahar generation by running the analysis on 11 different catchments threatening the Campanian Plain. The post-processing of the simulation outputs led to the production of hazard curves for the maximum flow thickness reached on a grid of points covering the Campanian Plain. By cutting the hazard curves at selected threshold values, we produce a portfolio of hazard maps and probability maps for the maximum flow thickness. We also produce hazard surface and probability maps for the simultaneous exceeding of pairs of thresholds in flow thickness and dynamic pressure. The latter hazard products represent, on one hand, a novel product in PVHA for lahars and, on the other hand, a useful means of impact assessment by assigning a probability to the occurrence of lahars that simultaneously have a relevant flow thickness and large dynamic pressure.

Lahars represent some of the most dangerous phenomena in volcanic areas for their destructive power, causing dramatic changes in the landscape with no premonitory signs and impacting the population and infrastructure. In this regard, the Campanian Plain turns out to be very prone to the development of these phenomena, since the slopes of the Somma–Vesuvius and Campi Flegrei volcanoes, along with the Apennine reliefs, are mantled by pyroclastic deposits that can be easily remobilized, especially after intense and/or prolonged rainfall. This study focuses on the analysis of pyroclastic fall and flow deposits and of the syn- and post-eruptive lahar deposits related to two sub-Plinian eruptions of Vesuvius in 472 CE (Pollena) and 1631. To begin with, historical and field data from the existing literature and from hundreds of outcrops were collected and organized into a database, which was integrated with several new pieces of data. In particular, stratigraphic, sedimentological (facies analysis and laboratory), and archeological analyses were carried out, in addition to rock magnetic investigations and impact parameter calculations. The new data are also referenced to the finding of ash beds in more distal areas, which were included in new isopach maps for the two sub-Plinian eruptions. The results show that for both eruptions the distribution of the primary deposits is wider than previously known. A consequence of these results is that a wider areal impact should be expected in terms of civil protection, as the sub-Plinian scenario is the reference one for a future large eruption of Vesuvius. Such a distribution of the pyroclastic deposits directly affects the one of the lahar deposits, also because a significant remobilization took place during and after the studied eruptions, which involved distal phreatomagmatic ash. From these integrated analyses, it was possible to constrain the timing of the deposition and the kind of deposits remobilized (pyroclastic fall vs. flow), and it was possible to calculate the velocities and dynamic pressures of the lahars and ultimately infer the lahar transport and emplacement mechanisms. The multidisciplinary approach adopted in this work shows how it is crucial to assess the impact of lahars in densely populated areas even at distances of several to tens of kilometers from active volcanoes. This especially applies to large parts of the densely populated areas around Somma–Vesuvius up to the nearby Apennine valleys.

Lahars represent some of the most dangerous phenomena in volcanic areas for their destructive power, causing dramatic changes in the landscape with no premonitory signs and impacting on population and infrastructures. In this regard, the Campanian Plain turns out to be very prone to the development of these phenomena, since the slopes of the Somma-Vesuvius and Campi Flegrei volcanoes, along with the Apennine reliefs are mantled by pyroclastic deposits that can be easily remobilised, especially after intense and/or prolonged rainfall. This study focuses on the analysis of the pyroclastic fall and flow deposits and of the syn- and post-eruptive lahar deposits related to two sub-Plinian eruptions of Vesuvius, 472 AD (Pollena) and 1631. To begin with, historical and field data from the existing literature and from hundreds of outcrops were collected and organized into a database, which was integrated with several new pieces of data. In particular, stratigraphic, sedimentological (facies analysis and laboratory) and archaeological analyses were carried out, in addition to rock magnetic investigations and impact parameter calculations. The new data are mainly referred to the finding of ash beds in more distal areas, which was included into new isopach maps for the two sub-Plinian eruptions. The results show that for both the eruptions the distribution of the primary deposits is wider than the one previously known. A consequence of these results is that a wider areal impact should be expected in terms of civil protection, as the sub-Plinian scenario is the reference one for a future large eruption of Vesuvius. Such distribution of the pyroclastic deposits directly affects the one of the lahar deposits, also because a significant remobilization took place during and after the studied eruptions which involved the distal phreatomagmatic ash. From these integrated analyses, it was possible to constrain the timing of the deposition and the kind of deposits remobilized (pyroclastic fall vs. flow), as well as was possible to calculate the velocities and dynamic pressures of the lahars, and ultimately infer the lahar transport and emplacement mechanisms. The multidisciplinary approach adopted in this work shows how it is crucial to assess the impact of lahars in densely populated areas even at distances of several to tens of km from active volcanoes. This especially applies to large parts of the densely populated areas around Somma-Vesuvius up to the nearby Apennine valleys.

Lahars represent some of the most dangerous phenomena in volcanic areas for their destructive power, causing dramatic changes in the landscape with no premonitory signs and impacting on population and infrastructures. In this regard, the Campanian Plain turns out to be very prone to the development of these phenomena, since the slopes of the Somma-Vesuvius and Campi Flegrei volcanoes, along with the Apennine reliefs are mantled by pyroclastic deposits that can be easily remobilised, especially after intense and/or prolonged rainfall. This study focuses on the analysis of the pyroclastic fall and flow deposits and of the syn- and post-eruptive lahar deposits related to two sub-Plinian eruptions of Vesuvius, 472 AD (Pollena) and 1631. To begin with, historical and field data from the existing literature and from hundreds of outcrops were collected and organized into a database, which was integrated with several new pieces of data. In particular, stratigraphic, sedimentological (facies analysis and laboratory) and archaeological analyses were carried out, in addition to rock magnetic investigations and impact parameter calculations. The new data are mainly referred to the finding of ash beds in more distal areas, which was included into new isopach maps for the two sub-Plinian eruptions. The results show that for both the eruptions the distribution of the primary deposits is wider than the one previously known. A consequence of these results is that a wider areal impact should be expected in terms of civil protection, as the sub-Plinian scenario is the reference one for a future large eruption of Vesuvius. Such distribution of the pyroclastic deposits directly affects the one of the lahar deposits, also because a significant remobilization took place during and after the studied eruptions which involved the distal phreatomagmatic ash. From these integrated analyses, it was possible to constrain the timing of the deposition and the kind of deposits remobilized (pyroclastic fall vs. flow), as well as was possible to calculate the velocities and dynamic pressures of the lahars, and ultimately infer the lahar transport and emplacement mechanisms. The multidisciplinary approach adopted in this work shows how it is crucial to assess the impact of lahars in densely populated areas even at distances of several to tens of km from active volcanoes. This especially applies to large parts of the densely populated areas around Somma-Vesuvius up to the nearby Apennine valleys.