The session welcomes contributions presenting research on the observation, modeling, and forecasting of extreme hydro-geological processes typical of Mediterranean and Mediterranean-like climates. Particular emphasis is placed on studies addressing the assessment, prediction, and mapping of hazard scenarios, with the aim of improving the evaluation and forecasting of hydro-geological risks. Contributions reconstructing past extreme hydro-geological events using paleohydrological, paleoclimatic, or related approaches are also welcome.
Mediterranean catchments are particularly prone to short-duration, high-intensity rainfall events that generate flash floods with significant impacts. Analyzing this type of event requires sub-daily hydrometric data in order to adequately capture their dynamics. This study investigates trends in flood characteristics across 38 Mediterranean basins in southern France, with an average size of 200km², using hourly discharge, radar rainfall, and reanalysis-derived soil moisture data over the period 1997–2024. Flood events are identified using a peaks-over-threshold approach and classified according to response time (flash-floods versus slower onset floods) and antecedent soil moisture conditions. Trends in flood peaks and direct runoff volumes are assessed using regional quantile regression after applying a spatiotemporal declustering procedure.
Results indicate increasing magnitudes for both flash floods and slow-onset floods under saturated soil conditions. These increases are more pronounced for flood volumes than for peak discharges, with trend magnitudes approximately twice as large. However, these results should be interpreted with caution given the pronounced spatiotemporal variability of flood processes in Mediterranean environments, given that the detected trends are not statistically significant based on a regional bootstrap assessment.
Overall, the results suggests that flood volume provides a more sensitive indicator of change than peak discharge in Mediterranean catchments. This underscores the importance of considering hourly data and process-based flood classification to improve the detection of evolving flood hazards in regions impacted by flash floods.
How to cite: Tramblay, Y., Arnaud, P., and Javelle, P.: Detecting trends in different types of floods in Mediterranean basins using hourly data, 19th Plinius Conference on Mediterranean Risks, Murcia, Spain, 6–9 Oct 2026, Plinius19-7, https://doi.org/10.5194/egusphere-plinius19-7, 2026.
Mediterranean agricultural areas may experience abrupt hydroclimatic contrasts, where long dry phases may be followed by concentrated rainfall sequences capable of triggering rapid landscape instability. In these contexts, soil erosion and gully activation are not only the consequence of a single storm, but the result of accumulated climatic and land-surface stressors acting on vulnerable soils. This contribution explores how a sequence of climatic stressors affected a cereal-crop gully system located near Casabermeja, Málaga, southern Spain, an area representative of Mediterranean agricultural landscapes affected by soil degradation, runoff concentration and irregular rainfall regimes. The study focuses on the transition between a markedly dry summer period and a subsequent winter storm train. During June–July 2025, the area received only 2.0 mm of rainfall over 61 days, including a 50-day dry spell. This antecedent dry state was followed by a persistent rainfall sequence between 21 January and 9 February 2026, with 234.8 mm accumulated in 20 days and a daily maximum of 76 mm. This contrast provides a suitable framework to examine how antecedent drought may condition the spatial response of agricultural soils to later rainfall extremes. To assess this response, two high-resolution UAV surveys were acquired before and after the storm sequence. Terrain and multispectral products were used to derive indicators related to topography, surface cover and hydrological organization. These variables were integrated into a machine-learning workflow designed to distinguish pre- and post-event surface conditions and to identify the main spatial controls of the observed response. The results indicate that the post-event pattern was mainly associated with hydrological connectivity and runoff concentration, while vegetation and surface-cover changes played a secondary, modulating role. This suggests that the impact of Mediterranean rainfall extremes depends strongly on the previous climatic state of the landscape and on the degree of soil vulnerability. By framing gully response as the outcome of interacting climatic stressors, this work provides a useful perspective for mapping erosion-prone areas and supporting adaptive soil-management strategies in Mediterranean agricultural environments.
How to cite: Moreno Cuenca, L. and Rodrigo Comino, J.: Climate stressors and hydrogeomorphological instability in Mediterranean agricultural soils: from drought to successive storm rainfall, 19th Plinius Conference on Mediterranean Risks, Murcia, Spain, 6–9 Oct 2026, Plinius19-14, https://doi.org/10.5194/egusphere-plinius19-14, 2026.
In literature it is assumed that an extreme is a rare, high (or low) magnitude event, where the concepts of rarity and magnitude depend on
the physical and temporal contexts. A statistical approach is presented to measure and communicate the magnitude of hydrological events and identify extremes. The core of the method is the frequency analysis of time series and the transformation of any data probability distribution into a standard normal distribution, where the event magnitude is expressed by the Z value, which is dimensionless. It provides a probability-based measuring scale that is invariant from the nature and variance of the hydrological phenomena and the spatial context. The Z value has the same properties as standardized indices, such as the well-known Standardized Precipitation Index (SPI), used in drought monitoring. An “extreme” is defined as an event with magnitude Z ≥ 2 (upper tail) or ≤ –2 (lower tail), depending on the nature of the hydrological variable.
The “extreme event” definition proposed does not contain any details about the event’s impact on the ground surface. These impacts depend on both the event magnitude (e.g., rainfall intensity) and land use or anthropogenic modifications of the natural environment as well. Furthermore, any geomorphological and hydrological processes, such as landslides and floods, depend on additional hydrological factors, including the pre-event wetness conditions of the soil, which could dump or amplify the event impact on the ground surface. Thus, the association between the Z value (event magnitude) and its impacts on the Earth surface could not be direct.
The Z value would provide a more suitable representation of the event magnitude than return period, commonly adopted to express the rarity or exceptionality of hydrological phenomena, as it represents a more stable scale, especially in the tails of the distribution. However, its use does not reduce intrinsic uncertainty and complexity of the probablity model.
How to cite: Leone, G. and Fiorillo, F.: A new classification of the magnitude of hydrological events and extremes using the Z value, 19th Plinius Conference on Mediterranean Risks, Murcia, Spain, 6–9 Oct 2026, Plinius19-11, https://doi.org/10.5194/egusphere-plinius19-11, 2026.
Flood frequency estimates derived exclusively from local discharge records are strongly influenced by limited sample sizes and by the extrapolation of the upper tail, which can result in unrealistically discharge quantiles. The framework of the design storm paradigm is too simplistic compared with the actual spatio-temporal variability of precipitation and hydrological processes. The catastrophic October 2024 flood in southern Valencia Metropolitan Area (Spain) offers a unique opportunity to revisit flood frequency analysis under such conditions.
To address these issues, the present study integrates regional precipitation analysis, stochastic weather generation, and distributed hydrological modelling. , the proposed approach better constrains the range and frequency of rainfall-runoff conditions capable of producing extreme flows.
As a consequence, discharge magnitudes previously associated with very long return periods are shown to occur more frequently, implying lower discharge values for a given return period and a higher effective frequency of potentially damaging flows. At the same time, we found a significant difference between the return period of the precipitation of the 2024 event (above a 2,000 years), the flows generated in some tributaries (below 500 years) and that of the main inundation (around 1,000 years).
How to cite: Francés, F., Aranda, J. Á., and Beneyto, C.: The flood frequency analysis of the catastrophic flash flood event of October 2024 in southern Valencia, 19th Plinius Conference on Mediterranean Risks, Murcia, Spain, 6–9 Oct 2026, Plinius19-134, https://doi.org/10.5194/egusphere-plinius19-134, 2026.
The AMARNA Platform contains a catalogue of 12,000 episodes of adverse meteorological conditions in Spain, covering the last 1,000 years. This enables studies to be carried out on flood events, covering not only current episodes but also those of greater severity and lower frequency that have occurred in climatic and historical contexts different from the present day.
This study aims to assess the most severe flood episodes to have occurred in Spain over the last 750 years (1275-2025). For this purpose, the available records identify up to 5,438 episodes in which some type of flood occurred, whether caused by rain, rivers or tides. An initial selection of episodes focused on those that resulted in at least one case of river overflow leading to the complete destruction of a building or infrastructure (including houses, bridges, water mills, dams or canals) and that led to evacuations, rescues, injuries or fatalities. This resulted in 271 episodes.
For these events, composite indices are derived by weighting the values of certain numerical variables: the structural impact index, the human impact index, the number of affected river basins, and the density of overflow records comprising the event. A list of 53 major events is compiled, to which two different weighting schemes are applied: one emphasising the structural impact component and the other the human impact.
The results provide a continuous historical overview of the severity of the various episodes, highlighting that those with the greatest structural impact occur during climatic fluctuations already recognised during the Little Ice Age for their high frequency of such phenomena. Whereas since the second half of the 20th Century, the severe episodes that have occurred, including the late October 2024 Valencia area episode, have had a greater impact on people than on buildings and infrastructures. This well-documented divergence may contribute to our understanding of mechanisms for the prevention and management of such emergencies. However, it also highlights that, on a historical scale, episodes with significant destructive potential have occurred and could recur in the current context, with a substantially increased population and similarly high levels of vulnerability.
Acknowledgements:
The authors acknowledge the grants from FLOODMED (PID2024-157662OB-C22), funded by the Spanish Ministry of Science, Innovation and Universities (MICIU/AEI/10.13039/501100011033) and by ERDF/EU.
How to cite: Barriendos, M., Barriendos, J., Gil-Guirado, S., Pérez-Morales, A., and Pino, D.: Study of major flood events in Spain over the last 750 years, 19th Plinius Conference on Mediterranean Risks, Murcia, Spain, 6–9 Oct 2026, Plinius19-67, https://doi.org/10.5194/egusphere-plinius19-67, 2026.
Mediterranean extreme weather events are often characterized by intense rainfall over short time periods and rapid hydrological response, making the short-term river water-level prediction a crucial component of flood early warning. In this work, we present the development and the pilot application of a data-driven operational prediction system for river water-level in multiple points in the region of Thessaly, Greece, based on artificial intelligence techniques.
The system exploits high temporal resolution observations from a regional network of meteorological and hydrometeorological stations in Thessaly, Greece, combining past rainfall data with river water-level data over a five-year period. The framework is designed to learn the nonlinear relationship between the antecedent rainfall and the subsequent evolution of the river stage (hydrological response). Several artificial-intelligence models, including gradient boosting machines and neural networks, are trained and evaluated to provide short-term water lever predictions at selected points of the network, with a prediction horizon up to 12 hours.
The preliminary results highlight the potential of artificial-intelligence techniques to real-time flood prediction in Mediterranean environments, providing valuable lead time for the local authorities and improved flood-risk preparedness.
Keywords: early warning systems, rainfall, river water level prediction, artificial intelligence
How to cite: Giannaklis, C.-P., Lagouvardos, K., Kotroni, V., Dimitriou, E., Papadopoulos, A., and Giannaros, C.: An Artificial-Intelligence-based application for short-term river water-level prediction and flood early warning in Thessaly, Greece. , 19th Plinius Conference on Mediterranean Risks, Murcia, Spain, 6–9 Oct 2026, Plinius19-28, https://doi.org/10.5194/egusphere-plinius19-28, 2026.
Rapid urbanization, aging drainage infrastructure, and increasingly heavy rainstorm events have made urban pluvial flooding a major problem for modern cities. Urban planning, risk assessment, and mitigation strategy design all depend on accurate modeling of these types of floods. However, the quality of the input data, especially the topographic information controlling overland flow and the depiction of drainage networks, has a significant impact on the model's effectiveness. Despite their acknowledged significance, these kinds of input data are frequently chosen based more on availability than on a methodical assessment, which could result in inaccurate flood forecasts.
This study examines how preprocessing and input data quality affect urban pluvial flood simulations, with a focus on 1D–2D coupled modeling.
The interactions between subterranean drainage systems and overland runoff are explicitly represented using an integrated framework that combines SWMM for one-dimensional (1D) drainage dynamics and IBER for two-dimensional (2D) surface flow. The study develops a fully coupled 1D–2D IBER–SWMM framework to overcome the drawbacks of purely 2D simulations, allowing dynamic and bidirectional water exchange between the surface and the drainage network. Municipal datasets were used to obtain inlet locations and typologies.
The 1.43 km² study area is a heavily populated part of the Sampierdarena district that is regularly impacted by pluvial floods brought on by rainfall events with very short return periods (3 years).
All things considered, this study highlights the crucial significance of methodical terrain data selection and preprocessing in 1D–2D coupled urban flood models. The fundamental methodological development that improves the physical consistency of surface–subsurface interactions and boosts predictive reliability is the merging of IBER and SWMM. The study offers a structured framework for more transparent and reliable urban flood simulations by clearly quantifying the impact of topographic data attributes on hydrodynamic outcomes. In light of growing hydrological extremes, our contribution promotes robust and data-driven urban flood risk management, supporting both scientific advancement and practical decision-making.
How to cite: Boni, G., Acquilino, M., Gnecco, I., Palla, A., Russo, B., and Sanz Ramos, M.: Impact of preprocessing and input data quality on urban pluvial flood simulations, with focus on 1D–2D coupled modelling. The case of Sampierdarena district of Genova using Iber-SWMM, 19th Plinius Conference on Mediterranean Risks, Murcia, Spain, 6–9 Oct 2026, Plinius19-102, https://doi.org/10.5194/egusphere-plinius19-102, 2026.
This study assesses coastal flood exposure and direct economic damages associated with 100-year return-period extreme sea-level events in five vulnerable Spanish coastal hotspots: the Ebro Delta, Alcudia Bay, the Albufera of Valencia, the Mar Menor and Doñana. The analysis considers two time horizons, 2050 and 2100, and two climate change scenarios, RCP 4.5 and RCP 8.5, using high-resolution geospatial flood layers, land-use information and projected land-use change scenarios.
The methodology combines GIS-based spatial analysis, land-use change modelling with MOLUSCE, and depth–damage functions adapted to Spanish land-use categories. Flooded areas were quantified by land use and study area, while direct economic damages were estimated for the modelled flood footprint of each 100-year extreme sea-level scenario. These estimates were calculated for both current land uses and future land-use projections. In addition, potentially developable urban land exposed to coastal flooding was identified to support territorial planning and adaptation strategies.
Results show a strong increase in exposure towards the end of the century. Total flooded area rises from 4,926 ha under RCP 4.5 in 2050 to 28,915.3 ha under RCP 8.5 in 2100. The most affected land uses are rice fields and coastal lagoons, followed by marshes, salt flats and beaches. Event-based direct economic damages for current land uses increase from €109.2 million in 2050 under RCP 4.5 to €808.8 million in 2100 under RCP 8.5, while future land-use projections raise potential damages to more than €1.0 billion in the most severe scenario. The Ebro Delta and the Albufera of Valencia concentrate the largest flooded areas, whereas urban and tourist-related land uses drive the highest estimated economic losses in the Mar Menor and Alcudia Bay, highlighting the key role of urban exposure in determining local economic vulnerability.
The authors gratefully acknowledge the support and funding received from project 22697/PI/24 (ISANMAR), funded by FSRM/10.13039/100007801. This work was also supported by the SHIELD project, funded through the EUniWell Well-Being Research Incubator Programme and Seed Funding Programme of the EUniWell Consortium (European Universities for Well-Being, https://www.euniwell.eu/), within the European Union’s Horizon 2020 research and innovation programme under Grant Agreement No. 101035821.
How to cite: Amor Amor, J. F., Mirete Hernandez, J., Gil-Guirado, S., and Montavez, J. P.: Event-based assessment of coastal flood damages under 100-year extreme sea-level scenarios in Spanish coastal hotspots, 19th Plinius Conference on Mediterranean Risks, Murcia, Spain, 6–9 Oct 2026, Plinius19-79, https://doi.org/10.5194/egusphere-plinius19-79, 2026.
Braided rivers constitute fluvial systems of high morphological complexity and significant geomorphological
dynamism. This study analyses the morphological dynamics and braiding intensity of the San Carlo reach
of the Fiumara Amendolea for the period 2022–2024. The Fiumara presents optimal characteristics for the
development of the braiding model: it is a short, steep, ephemeral and torrential watercourse with scarce riparian
vegetation. The analysis of braided systems, such as the one studied here, is key in the context of climate
change, where an increase in the frequency of extreme precipitation events is expected. For the analysed period,
a simplification of the network is observed, a phenomenon that can be attributed to torrential precipitation
episodes recorded during the study period. The methodology integrates photogrammetric processing using
Structure from Motion (SfM) of multispectral UAV/RPAS surveys, GIS-based spatial analysis, and automated
channel network extraction using RivGraph. To measure braiding intensity, four braiding indices (BI) —Brice,
Germanoski-Schumm, Mosley, and the Entropic Braiding Index (eBI; Tejedor et al., 2022)— were computed
for each sub-reach of both the full channel and the most active reach. Additionally, a series of morphological
indices and variables were calculated to establish correlation relationships with the BIs, in order to determine
which of these is most representative of the spatial reality of the Fiumara Amendolea. The results reveal a
generalised reduction pattern in braiding intensity over the analysed period, with alternation of the dominant
geomorphological process; in the headward sector of the San Carlo reach, sedimentation prevails, whereas
incision dominates downstream.
Keywords: braided channels, BI, eBI, Amendolea Fiumara, fluvial geomorphology, SfM photogrammetry,
multitemporal analysis.
How to cite: Bellido Solano, Á., Foti, G., Bombino, G., Pérez Cutillas, P., and Conesa García, C.: Morphological change indicators in a semi-arid braided system, the Fiumara Amendolea (Calabria, Italy): multi-temporal evaluation and analysis, 19th Plinius Conference on Mediterranean Risks, Murcia, Spain, 6–9 Oct 2026, Plinius19-114, https://doi.org/10.5194/egusphere-plinius19-114, 2026.
Volcanic pyroclastic deposits (tephra) constitute complex granular systems whose macroscopic geomechanical stability is closely linked to microscopic interfacial forces. In the ash fraction from tephra, cohesion is heavily influenced by surface free energy components and their response to environmental parameters like pH and ionic strength. This study evaluates the surface thermodynamic properties of four reddish pyroclastic tephra samples—known as Almagres—collected from distinct geological context of Deception Island (Antarctica), labeled SPLD(5), SPLD(9), SPLD(19), and SPLD(25). To unravel the underlying physicochemical mechanisms governing their cohesion, the surface free energy components were determined and interpreted quantitatively using the Van Oss-Chaudhury-Good theory
The experimental results reveal a pronounced thermodynamic heterogeneity among the samples, reflecting variations in their mineralogical and alteration states. Applying the Van Oss framework allowed for the decoupling of apolar Lifshitz-van der Waals (γLW) and polar Lewis acid-base (γAB) interactions. Sample SPLD(5) exhibits a strictly monopolar electron-donor behavior, characterized by a significant basic component γ- = 66.00 mJ/m2 but completely lacking an acid contribution γ+ = 0.00 mJ/m2, resulting in a null polar component γAB = 0.00 mJ/m2 and a total surface energy γTot equal to its apolar value 43.40 mJ/m2. Conversely, sample SPLD(25) demonstrates a highly active bipolar (amphoteric) character, yielding the highest total surface energy γTOT = 100.53 mJ/m2 and a remarkably strong electron-acceptor component (γ+= 23.40 mJ/m2.
These surface energy variations directly dictate the samples' interaction with the interstitial aqueous phase, as quantified by the work of adhesion to water Wa. The water affinity ranges from a minimum of 126.9 mJ/m2 for the moderately polar SPLD(19) to a maximum of 159.7 mJ/m2 for the highly polar SPLD(25). It is concluded that the varying polar and apolar surface profiles of these Almagres crucially modulate interparticle capillary bridges and adhesion under shifting geochemical conditions. Furthermore, the insights gained from this unaltered polar analog provide a valuable predictive framework for Mediterranean anthropized volcanic systems, where similar fluid-particle interactions dictate geomechanical risks in active volcanic edifices.
How to cite: Moleón, J. A., Ontiveros, A., Giménez, E., Abad, M. I., Ureña, M., and Sánchez-Gómez, M.: Surface Free Energy Characterization of Reddish Volcanic Tephra (Almagres) from Deception Island: Implications for Granular Cohesion, 19th Plinius Conference on Mediterranean Risks, Murcia, Spain, 6–9 Oct 2026, Plinius19-64, https://doi.org/10.5194/egusphere-plinius19-64, 2026.
The AMARNA Platform (Multidisciplinary Archives for the Analysis of Natural and Anthropogenic Risks) is an initiative designed to collect, catalogue and classify the extreme meteorological events that have occurred in Spain over the last 1,000 years.
One part of AMARNA is a repository containing records of information from primary documentary sources and bibliographic sources, in the form of graphical and textual files. The other part consists of digital files containing the basic details of the catalogued cases and episodes.
This compilation effort provides access to over 42,000 daily records, organised into 12,000 episodes, with the possibility of gradually integrating all the information and processing it using the same procedures and criteria, whether it relates to historical or current periods. The thematic scope is also sufficiently broad, allowing for the cataloguing of all kinds of adverse meteorological phenomena and their effects on the ground, such as floods or droughts. Furthermore, the cataloguing of social impacts is included, whether due to problems with water resources, public health or food supplies.
AMARNA has a classification system designed to provide a quantitative assessment of records relating to the adverse weather phenomena most prevalent across the Iberian Peninsula: droughts and floods.
Acknowledgements:
The authors acknowledge the grants from FLOODMED (PID2024-157662OB-C22), funded by the Spanish Ministry of Science, Innovation and Universities (MICIU/AEI/10.13039/501100011033) and by ERDF/EU.
How to cite: Barriendos, M., Barriendos, J., Gil-Guirado, S., Pérez-Morales, A., and Pino, D.: The AMARNA Platform as a resource for knowledge of extraordinary meteorological events on the Spanish Mediterranean Basin on a historical scale, 19th Plinius Conference on Mediterranean Risks, Murcia, Spain, 6–9 Oct 2026, Plinius19-66, https://doi.org/10.5194/egusphere-plinius19-66, 2026.
This paper examines drought detection in Italian catchments through a historical analysis of two meteorological indices: the Standardized Precipitation Index (SPI) and the Standardized Precipitation Evapotranspiration Index (SPEI) evaluated on the basis of the BigBang database (www.isprambiente.gov.it/pre_meteo/idro/BIGBANG_ISPRA.html) by the Italian Higher Institute for Environmental Protection and Research (ISPRA). The study focuses first on the characterization of drought indices into different scenarios and then a counting process based on statistical testing using a non-homogeneous Poisson process (NHPP) was applied to drought trends within each raster dataset. Finally, the proportion of drought trends within each catchment is determined based on the trends observed in individual raster grid cells. Hotspot analysis of drought indices is also conducted for each catchment, considering seasonal variations and geographic divisions across Italy. The results show that the Adige catchment, located in the Alpine region, exhibits the lowest drought index values during winter for both SPI and SPEI, which is consistent with the precipitation and evaporation patterns observed in Italian catchments.
How to cite: Masoumi Shahrbabak, M., Roth, G., Taramasso, A. C., and Boni, G.: A raster-based non-homogeneous Poisson process approach for drought trends detection in Italian catchments, 19th Plinius Conference on Mediterranean Risks, Murcia, Spain, 6–9 Oct 2026, Plinius19-119, https://doi.org/10.5194/egusphere-plinius19-119, 2026.
Coastal flooding driven by sea-level rise is expected to become one of the most significant climate-related hazards affecting low-lying coastal regions worldwide during the coming years. Along the Mediterranean coast, where population, economic activities, and critical infrastructures are highly concentrated near the shoreline, even moderate increases in sea level may substantially increase flood exposure and associated economic losses. Assessing future coastal flood impacts is therefore essential to support adaptation planning and risk management strategies.
However, projections of future coastal flooding are subject to considerable uncertainty. These uncertainties arise from differences among climate scenarios, sea-level rise projections, storm surge contributions, local coastal morphology, and the representation of hydrodynamic processes. As a result, impact assessments based on a limited number of future scenarios may provide an incomplete picture of the range of possible outcomes and their associated risks.
To address this issue, we propose a high-resolution framework that generates inundation and damage functions for a continuous range of sea-level rise values over the Spanish Mediterranean coast. For this objective, we developed a very fast hydraulically connected flood model and applied it to a very detailed topographic data (5m). The analysis of these functions allows the identification of critical behaviour, defined as the threshold beyond which inundated areas and economic damages increase abruptly in response to relatively small additional increases in sea level. The identification of such critical points provides valuable information for climate adaptation planning, enabling the prioritization of preventive measures before the most severe impacts are triggered.
Acknowledgements: This work was supported by the INSIEME and ISANMAR projects (FSRM/10.13039/100007801).
How to cite: Montavez, J. P., Mirete, J., and Gil-Guirado, S.: Tipping Points in Coastal Flood Risk : High-Resolution Inundation and Damage Functions under Sea-Level Rise in the Spanish Mediterranean coast, 19th Plinius Conference on Mediterranean Risks, Murcia, Spain, 6–9 Oct 2026, Plinius19-76, https://doi.org/10.5194/egusphere-plinius19-76, 2026.
