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A series of flowslide impact tests was developed in a beam centrifuge with natural silty-sandy volcanic soils sampled on mountain slopes near Vesuvius volcano in Italy. Following the release of the material, the flow propagates up to the impact loading stage, exhibiting different flow–barrier interaction mechanisms. High-frequency image acquisition and processing are used to quantify the flow-structure interaction, which is then interpreted through an advanced large deformation numerical approach based on the Material Point Method (MPM), capable of including the hydromechanical behavior of non-associative elastoplastic materials such as those composing the flow and the barrier. The MPM model is calibrated on barrier displacement dynamics, which range from negligible values to 0.18 m depending on barrier position and released mass, and validated against flow arrival time, thickness and velocity of flow before the impact and load cell time measurements of base vertical total stress. Back-analysis reveals that saturated hydraulic conductivity ranges from 9.81e-4 m/s to 9.81e-3 m/s across the four selected tests, with lower conductivity values correlating with greater energy transfer to the barrier and a transition in interaction mechanisms from “bore” to “standing jump” and “airborne jet”. The most frequently observed mechanism is the standing jump, characterized by flow run-up, partial overtopping, and material accumulation behind the barrier. As the main novelty, the saturated conductivity of the flow under impact conditions is quantified within a physically consistent range, which is outlined as a key factor in the whole process, including propagation, interaction, and dissipation. These results provide essential insights for engineering practice in debris flow hazard mitigation, particularly for the design and assessment of protective barrier systems. While the centrifuge tests provide controlled conditions enabling detailed observation of flow-barrier interactions, the study considers a single soil type and simplified barrier geometry. Future research should investigate the influence of varying fine content, partial saturation conditions, and flexible barrier designs to extend the applicability of these findings to diverse landslide mitigation scenarios. • Centrifuge tests at 40 g simulate debris flow impact on a free-sliding barrier. • Numerical MPM model calibrated using the barrier's experimental data. • Calibration was performed on soil permeability and Young modulus. • Model validated by comparing numerical and experimental total vertical stresses. • Results compared with existing literature through Faug's diagram.

Abstract. In this paper, we explore five core challenges that need to be addressed in order to move towards the Comprehensive Disaster and Climate Risk Management approach, which has been proposed within the newly emerging paradigm of a more holistic approach to managing the risks associated with climatic and/or non-climatic hazards and non-climatic risk drivers across varied time scales and levels. These five challenges relate to the following points. First, we have a lack of comprehensive and high quality data for observing how society is impacted by, prepares for, and responds to multi-risks. Second, as a result we have a limited understanding of why individuals, communities, and other decision-makers (fail to) prepare for complex multi-risks in the way they do, and how that affects their responses. Third, our capacity to simulate how current and future risk could be effectively reduced is hampered by the aforementioned lack and fragmentation of observations and understanding of multi-risk dynamics. Fourth, current governance structures often reinforce data and knowledge silos. Fifth, the high complexity and wicked nature of the multi-risk problem results in barriers in knowledge exchange at the science, policy and practice interface. In this paper, we elaborate on each of these challenges, discuss why they matter for comprehensive disaster risk management, and provide ideas of how to overcome these challenges. We end the paper with a brief outlook.

Abstract Rivers are increasingly fragmented and degraded, yet the European Union Nature Restoration Regulation calls for restoring at least 25,000 kilometres of free-flowing rivers by 2030. Translating this ambition into effective implementation remains challenging because restoration priorities differ across ecological, social, economic, and governance contexts. Here, we synthesize expert knowledge from 45 countries through a structured, multi-step prioritization process to identify research priorities for restoring free-flowing rivers in Europe. We identified 27 priorities and analysed how expert background and spatial context influenced their ranking. Restoration priorities differed systematically depending on whether experts emphasized ecological integrity, community engagement, economic considerations, or governance capacity, revealing clear patterns in how disciplinary and professional perspectives shape implementation pathways. This demonstrates that restoration strategies cannot be universal but must be adapted to local and regional political, institutional, and ecological conditions. Building on these findings, we propose a structured prioritisation framework that links barrier removal, connectivity restoration, governance mechanisms, and policy instruments to context-specific needs. Together, our results provide an empirically grounded and implementation-oriented roadmap to support European Union Member States in delivering ambitious river restoration targets in a context-sensitive and socially robust manner.

Abstract. This study compares operational Flood Forecasting and Early Warning Systems (FFEWSs) in transboundary river basins in Northwestern Europe, covering parts of Luxembourg, Germany, The Netherlands and Belgium. This region was hit by an extreme flood event in 2021 with more than 200 fatalities. Due to the high death toll and the large number of people who did not receive warnings, the FFEWSs were heavily criticized afterward. This study shows strong improvements in FFEWSs after the flood event in all countries. Interviews with experts across the region reveal that warning thresholds are optimized, some regions include new warning thresholds for extreme events (e.g. dark purple), and flood crisis management plans are improved. In addition, all countries now use mobile phone-based alerts using cell broadcasting technology. The assessment of the warning systems shows strong differences between and within countries, with different flood warning levels and warning colour codes in use. The interviews also reveal that the adoption of operational impact-based forecasts remains a challenge, while these are crucial for translating hydrological forecasts into effective actions. For example, the interviewees stress the need for operational flood inundation forecasts, which are currently only provided in Flanders. Our study has four concrete recommendations: (1) investigate the benefit of streamlined warning levels and colour codes between and within different countries; (2) assess the added value of more extreme warning levels for catastrophic events, such as the purple levels in Luxembourg and some German regions; (3) accelerate the development of operational impact-based forecasting systems, and (4) implement a structural evaluation of warning communication chains. These challenges must be addressed to reduce the gap between early warning and early action during impactful flood events.

Rivers in regions with cold winters can seasonally freeze up. River ice breakup and freeze-up processes can lead to river ice jams, which are a major contributor to flood risk in cold regions (across most of the high latitudes of the northern hemisphere). In Canada, satellite remote sensing is used across the country to provide timely information on the status of river ice. Methods and algorithms to classify various stages of river ice from the Radarsat Constellation Mission (RCM) are available, but the operational implementation of these, especially the integration into larger flood forecasting and early warning systems, requires specific expertise, software and computational resources, and comes with its own set of challenges. In collaboration with various agencies across Canada we have set up operational monitoring systems with the purpose of assisting the daily tasks of forecasters on duty. These have been used in practice over multiple ice breakup and freeze-up seasons, which has highlighted both their usefulness and shortcomings. We will focus on various aspects of such a system and share lessons learned on its design, setup and operational use, as well as a framework to analyse various factors relevant for operational monitoring purposes (e.g. spatiotemporal coverage and latency of the data, critical elements in the support of decision-making relating to floods). In this, we do not shy away from problems and pitfalls, so that others can learn from these. While various challenges remain, this work is a good example of the value in the joint engagement of applied science and end users.

Defining literacy is essential because it establishes a baseline for education, enables robust assessment and measurement of progress, supports policy and accountability, makes domain-specific differences explicit, and can improve equity by enabling better-designed interventions to promote learning. UNESCO notes that, beyond its conventional concept as a set of reading, writing and counting skills, literacy is now understood as a means of identification, understanding, interpretation, creation, and communication in an increasingly digital, text-mediated, information-rich and fast-changing world. Consequently, multiple domain literacies have emerged, including science, health, media, digital and financial literacy, and more recently AI literacy. While ocean literacy has gained significant traction in the last decade, for the coast an early coastal literacy framework was proposed in 2010 by CoastNet (UK charity that has since closed), but it was primarily oriented towards integrated coastal zone management. The objective of this work is thus to define coastal literacy and what it comprises.To develop a definition tailored to coastal contexts, related literacy constructs were reviewed, particularly ocean literacy, climate literacy and risk literacy. Across frameworks, literacy is commonly articulated through dimensions (for example, knowledge, awareness and attitudes) and, in some cases, through explicit principles. The Ocean Literacy Framework is a prominent example, currently comprising seven principles and 45 concepts, and defines ocean literacy as understanding the ocean’s influence on humanity and humanity’s influence on the ocean. Although coasts form part of the broader ocean system, coastal environments have distinct characteristics: they concentrate human activities, involve frequent and direct human–environment interactions, and are often exposed to hazards. Coasts also exist at the interface of multiple Earth system spheres, linking the ocean, land and atmosphere. The framework of coastal literacy was developed building on the literature review and on a two-day focus group using structured brainstorming methodologies. The proposed framework comprises seven principles: (P1) Each coast is unique and has value on its own; (P2) Coasts consist of many different and connected parts; (P3) Coasts are dynamic, changing from seconds to millennia; (P4) Human activities impact the coast, and coasts continually affect humans; (P5) Coasts are inherently hazardous environments that can place people and infrastructure at risk; (P6) Climate change is affecting coastal ecosystems and challenging future coastal use; and (P7) We share responsibility for looking after the coasts for present and future generations. A key contribution of these principles is how they frame human–coast relationships. They recognise the intrinsic coastal value independent of human use or resource exploitation (P1), position humans as part of coastal systems (P2, P4), explicitly foreground coastal risk (P5), and treat shared responsibility as a component of literacy (P7). They also embed sustainability by emphasising the need to safeguard future generations, including in the context of climate change (P6). Further work is needed to elaborate the concepts underpinning each principle and to refine the framework through additional validation; however, the principles presented here provide a structured foundation for defining and operationalising coastal literacy.

Extreme sea level (ESL) events, resulting from the combined effects of tides, storm surge, waves, and mean sea level rise, are a key driver of coastal flooding risk worldwide. While future increases in ESL magnitude and frequency due to anthropogenic climate change are well established, it remains unknown whether such changes, unlikely to be caused by internal variability alone, are already detectable in historical records, and whether their amplitude has emerged beyond the range of natural/internal variability at the global scale. Although a few studies have reported long-term increases in ESLs using historical tide-gauge records, the extent to which such changes are detectable and have emerged remains largely unknown, particularly at the global scale. This knowledge gap persists due to several challenges: (1) the infrequent, short-lived, and highly localized nature of ESL events, requiring high temporal and spatial resolution data; (2) the need for long, consistent time series to robustly characterize internal variability; and (3) the methodological complexity of detecting climate change signals and their emergence in extremes, compared to mean climate variables. Here, we assess the detection and emergence of climate change signals in ESLs along the global ice-free coastline using a 74-year (1950–2023) hydrodynamically modelled dataset with global coverage. Applying a detection and emergence framework tailored for extremes, we identify statistically significant increasing trends in ESL magnitude (global median 2.6 mm yr⁻¹) along approximately half of the global ice-free coastline. At nearly all computational points where a significant trend is detected, the associated ESL signal has already emerged beyond internal variability during the 1970–2023 period. The earliest times of emergence (regional-median ToE = between 1979 and 1982) occur in several IPCC reference regions, including the Equatorial Atlantic Ocean, Central Africa, the Equatorial Indian Ocean, Western Africa, Northeastern South America, Arabian Sea, and Northern South America. Linking times of emergence with national-level socio-economic indicators reveals that socioeconomically vulnerable countries with minimal historical CO₂ emissions have experienced increasing ESL magnitudes for the longest period.

Design-flood estimation for small fluvial catchments in the Benelux plus Germany region relies predominantly on simplified event-based methods, reflecting limited data availability and the absence of consistent regional guidelines. While such approaches are widely applied in practice, key modelling choices are often unguided, leading to large uncertainty and inconsistent protection levels across regions. This study investigates how basin similarity, catchment storage, and geology can be used to improve the robustness of event-based flood estimation in data-fragmented settings. This study integrates high-resolution observations from a network of experimental and operational basins with hydro-meteorological records. Event-scale hydrological signatures relevant to event-based modelling (time to peak, rising-limb characteristics, peak discharge, and runoff coefficients) are derived and analysed across simple antecedent moisture conditions (AMC) classes. Basin similarity is assessed using a combination of physical descriptors and observed event responses, and basins are grouped into response classes using clustering techniques. Leave-one-basin-out testing is applied to evaluate the transferability of response characteristics within and across classes. A parsimonious event-based rainfall–runoff model, representative of methods commonly used in design-flood studies, is then applied. Model parameters are constrained using empirical ranges derived from observed events. Model experiments systematically vary response-time formulations, AMC assumptions, and parameter sources (regional data, proxy basin, or class-based values) to quantify their influence on simulated peak discharges. Sensitivity and robustness are evaluated across storage and geology classes. Results show that uncertainty in event-based design floods is dominated by response-time and AMC assumptions, and that similarity-based parameter transfer can reduce uncertainty in storage-controlled catchments but performs poorly where storage contrasts are large or data are sparse. The findings provide empirical guidance on when event-based regionalization is best suited and highlight structural limitations of current practice. This work supports the development of more consistent, evidence-based design-flood guidelines for small basins in the Benelux region.

This study presents a comprehensive risk assessment methodology tailored to the Cávado region, Portugal, an area vulnerable to flood hazards. The approach integrates the four core IPCC risk components (hazard, exposure, vulnerability, and response), leveraging open-source datasets to ensure transparency, replicability, and transferability. An index-based modelling framework is applied at 100m spatial resolution, combining flood simulations for multiple return periods (RP10, RP50, RP100, and RP500) to capture the spatial variability of flood risk.A key novelty of this work lies in the integrated assessment of multiple response indicators aimed at risk mitigation, with particular attention to the spatial distribution and accessibility of critical infrastructure, including healthcare and educational facilities. A network-based analysis is implemented to evaluate access to essential services under different flood scenarios, assessing both walking and driving modes. Travel distances and times from road nodes to health-related points of interest are quantified to support emergency response planning.The methodological framework was developed through continuous stakeholder engagement with regional authorities, involving an iterative dialogue to support data acquisition, define the baseline risk situation, jointly identify relevant Nature-based Solutions (NBS) to be modelled, and validate the modelling outcomes. Results include spatially explicit flood risk maps across different return periods, as well as an evaluation of how different response measures, including NBS, influence overall risk patterns. The proposed approach provides a robust, scalable, and policy-relevant tool to support data-informed decision-making in disaster risk reduction, emergency planning, health infrastructure investment, and climate adaptation strategies.

Flooding is one of the costliest natural hazards globally and is expected to increase in severity because of climate change and socio-economic developments. Therefore, it is important to implement adaptation measures that limit flood risk. Adaptation measures can be implemented by governments, but also households can flood-proof houses. This is viewed as a promising adaptation strategy, but it is unclear yet how many households will adopt these measures in response to government policies. Therefore, this study aims to understand to what extent various government policies, such as subsidies and information campaigns, can lead to increased implementation of household-level adaptation to reduce risk, such as wet-proofing or dry-proofing. To do so, we further develop a coupled hydrological, hydrodynamic, and agent-based model (GEB). We demonstrate this model for the Geul river in The Netherlands, where a severe flood event took place in July 2021.The GEB model simulates river discharge over the last 30 years, including the July 2021 flood. When discharge exceeds bankfull conditions, we automatically simulate the flood using the hydrodynamic model SFINCS. Households in flood-prone areas make adaptation decisions on an annual basis, and additionally reconsider their choices following a flood event. This decision-making process is based on the Subjective Expected Utility Theory. Following this theory, flooding elevates the flood risk perception of households and this increased perception triggers adaptation decisions.Our socio-hydrological simulations show that household adaptation is an effective way to reduce flood damages. Results can be used by policymakers to understand how much flood risk reduction can be achieved through household adaptation and to design strategies to increase adaptation uptake.