<p>Characterising and assessing multi-risk in complex systems is vital to realise the expected outcome of the Sendai Framework for Disaster Risk Reduction. As sectors and systems are increasingly interconnected, the space in which impacts cascade is expanding. This became apparent throughout the COVID-19 pandemic, but can also be seen in the compounding and cross-border effects of climate change and connected extreme events, or from global ripple effects of armed conflicts such as the aggression committed by Russia against Ukraine. Single-hazard and single-risk approaches, while useful in certain contexts, are becoming increasingly insufficient for comprehensively managing risk due to cross-sector and cross-system interactions. There is therefore a need to develop tools that can account for how multiple hazards interact with multiple vulnerabilities of interdependent systems and sectors, which requires a systemic perspective for assessing risks.</p><p>To this aim, we developed a novel analytical tool to characterise the interconnections between risks, their underlying hazards, risk drivers, root causes and responses to risks and impacts across different systems. The tool draws on the impact chains approach (i.e. conceptual models for climate risk assessment), expanding its linear and sectoral focus towards a system-oriented view. We follow the recommendation of Zebisch et al (2021) and name this tool ‘Impact Webs'. </p><p>We applied the tool to five case studies in Bangladesh, Ecuador, India, Indonesia and Togo to characterise and assess cascading risks linked to COVID-19, responses to it (e.g. restriction measures) and other hazards that co-occurred during the pandemic (e.g. hydrological, geophysical, climatological). The participatory co-development of the Impact Webs was led by local case study experts and involved desk research, stakeholder workshops and expert/community consultations.</p><p>These diverse applications at multiple scales showed that Impact Webs are useful to conceptualise and visualise networks of interconnected elements across sectors. Because of the tools suitability to simultaneously analyse the interactions of multiple hazards with multiple pre-existing vulnerabilities, it provided a representation of the multi-risk space in the case studies. This is promising to identify critical elements for further investigation, such as feedback effects, trade-offs and key agents that can influence risks in systems. To this aim, the tool not only accounts for negative impacts, but also how policy responses and societal reactions to policies can lead to additional positive outcomes, as well as unintended consequences, i.e. risks arising from responses. However, given the complexity of systems and system boundaries, it is not possible to characterise all interconnections using Impact Webs. While this simplification of reality is useful for communication purposes, only the most prominent outcomes of the tool are derivable, and although the participatory approach aims to reduce this, results can be influenced by inherent biases. Despite these challenges, we find that Impact Webs are a promising new approach to characterise and assess multi-risk, thereby supporting comprehensive disaster risk management. </p>

Current rapid urbanization trends in developing countries present considerable challenges to local governments, potentially hindering efforts towards sustainable urban development. To effectively anticipate the challenges posed by urbanization, participatory modeling techniques can help to stimulate future-oriented decision-making by exploring alternative development scenarios. With the example of the coastal city of Monastir, we present the results of an integrated urban growth analysis that combines the SLEUTH (slope, land use, exclusion, urban extent, transportation, and hill shade) cellular automata model with qualitative inputs from relevant local stakeholders to simulate urban growth until 2030. While historical time-series of Landsat data fed a business-as-usual prediction, the quantification of narrative storylines derived from participatory scenario workshops enabled the creation of four additional urban growth scenarios. Results show that the growth of the city will occur at different rates under all scenarios. Both the “business-as-usual” (BaU) prediction and the four scenarios revealed that urban expansion is expected to further encroach on agricultural land by 2030. The various scenarios suggest that Monastir will expand between 127–149 hectares. The information provided here goes beyond simply projecting past trends, giving decision-makers the necessary support for both understanding possible future urban expansion pathways and proactively managing the future growth of the city.

<p>In recent years, research on drought risk has expanded to include multiple types of drought hazards, various exposed elements and a multitude of factors that determine the vulnerability of a given system or sector. This has resulted in a call from the scientific community to adopt a systemic risk perspective on drought. However, a thorough understanding of how drought risks manifest, cascade and interact across different systems and sectors is still lacking, and methodological guidance on how to analyse and represent these interdependencies does not yet exist.  In order to explore these gaps, we have developed conceptual models of drought risks for key selected systems and sectors in the European Union. </p> <p>For each system and sector considered (rain fed and irrigated agricultural systems, forest ecosystems, freshwater ecosystems, public water supply, inland water transport and the energy sector), a conceptual model was constructed to depict how drivers and root causes interact to create drought risk. The models are based on the impact chains methodology and are informed by literature review and multiple expert consultations (including a series of validation workshops). Subsequently, the system-specific models were used to build an overarching conceptual model of the critical interdependencies that exist between all the systems and sectors considered. </p> <p>The analysis has revealed that, in each system, drought risks manifest through a complex web of interactions between drivers of risk, which are in part system-specific and in part shared across the systems considered. From this, multiple considerations for drought risk assessment and management can be derived. In particular, special attention should be placed in defining and representing what drought risk is in each system, as the underlying characteristics might greatly differ. Additionally, the use of conceptual models can constitute an important first step for risk assessment, as they contribute to addressing the complexity of drought risks. Finally, the existence of commonalities and interdependencies between systems implies that interventions can and must be designed so as to consider multiple systems at once, thus avoiding maladaptive solutions. In this sense, the conceptual models can serve as entry points for the identification of risk reduction and adaptation measures which go beyond the single-risk and single-sector perspective, thus contributing to a more systemic view on drought risk management and adaptation, as well as highlighting persisting knowledge gaps.</p>

Multi-risk assessments are being increasingly proposed as a tool to effectively support policy-makers in reducing impacts from natural hazards. The complexity of multi-risk requires assessment approaches capable of capturing multiple components of risk (e.g., different hazards, exposed elements, and dimensions of vulnerability) in a coherent frame of reference, while at the same time providing an intuitive entry point to allow participation of relevant stakeholders. Contributing to the emerging multi-risk literature, we carried out a multi-risk assessment for the Marrakech-Safi region (Morocco)—an important economic and demographic hub in the country that is prone to multiple natural hazards, most notably floods and droughts. Through multiple consultations with local experts and stakeholders, a multi-risk assessment framework was constructed based on a set of single-risks related to flood and drought hazards. For each risk, spatial analysis was employed to assess the hazard exposure component of multi-risk, while a set of vulnerability indicators and stakeholder-informed weights were used to construct a composite indicator of vulnerability at the municipal level. For each municipality, the set of indicators and weights contributing to the composite indicator was designed to be dependent on the combination of risks the municipality is actually confronted with. The two components were aggregated using a risk matrix approach. Results show a significant proportion of municipalities (28%) reaching very high multi-risk levels, with a large influence of drought-related risks, and a prominent contribution of the vulnerability component on the overall multi-risk results. While the approach has allowed the exploration of the spatial variability of multi-risk in its multiple sub-components and the incorporation of stakeholders' opinions at different levels, more research is needed to explore how best to disentangle the complexity of the final multi-risk product into a tool capable of informing policy-makers in the identification of entry points for effective disaster risk governance.