Agent-based modelling (ABM) is becoming a widely explored method for investigating human–water systems, given its ability to represent heterogeneous actors and their decisions. ABM can simulate how humans interact and co-adapt with their environment, which is beneficial for understanding the effects of humans’ decisions in the face of hazards and climate change. ABMs can serve as tools for examining the effects of current and future hydrological hazard management strategies. However, the implementation of hydrological hazard management in ABMs has not yet been systematically evaluated for floods and droughts. To map the current status of ABMs in hydrological hazard modelling and facilitate a discussion on further potential, we conducted a systematic mapping review based on the ROSES protocol. In this review, we investigate what kinds of hydrological hazards and management strategies that are represented in ABMs. Additionally, we synthesise current practices regarding agent types and their decision-making. A total of 377 articles were screened, and 77 articles were analysed in full text. Our findings indicate that hydrological hazard management strategies in ABMs include both structural and non-structural measures. However, there is an emphasis on the complexity of individual agents’ decision-making in implementing these measures, whereas collective agents (e.g. governments) performing non-individual hazard management are implemented more simplistically, often as static scenarios or collective agents with ad-hoc or rational decision-making. Conversely, individual agents are commonly implemented with human-like behaviour. Our study highlights that the simplicity of hazard management in these models could restrict the potential of ABMs as policy and predictive tools, as the implemented hazard management does not capture the full dynamics of human–water systems. Involving stakeholders, adopting interdisciplinary methods, or incorporating bounded-rational decision-making could represent a significant shift to further enhance the explanatory power of ABM for addressing challenges in hydrological hazard management.

Anthropogenic climate change is increasing the frequency and severity of droughts, which accelerate land degradation, harm ecosystems, and threaten water security and livelihoods. However, the global impact of prolonged droughts on land cover changes remains poorly studied. This research analyses precipitation data to identify drought conditions and compares them with land cover datasets. The analysis explored three analytical dimensions, over the period 1992-2021: country level, income level, and climatic level. Results show a strong connection between droughts and land cover changes, with low-income countries experiencing the most significant changes. In drought-prone areas, trees, cropland, and sparse vegetation are the most impacted, with correlations stronger than in unaffected regions. This study provides valuable insights into the complex relationship between global drought events and land cover changes, varying across regions and economic contexts, and highlights the mitigating role of proactive strategies such as sustainable land management and adaptation measures.

There is growing scientific and policy interest towards transitioning from conventional to sustainable systems to manage stormwater in urban areas. The literature has produced several contributions to prove the (often compound) benefit of nature-based solutions (NBS) and discussed challenges to their implementation. However, an open gap remains regarding NBS maintenance over time and how this might hinder a broad uptake. We conducted a comprehensive literature review of academic and technical documents that reveals five significant barriers linked to maintenance that might constitute an obstacle to the transition from grey to green approaches: importance of local context, unclear management responsibilities, lack of funding and incentives, uncertainty regarding long-term costs and performance, and mixed perceptions about maintenance requirements. The analysis also showed how maintenance is more a governance than a technical challenge, and we argue that this arises from its multi-disciplinary knowledge base, increased system complexity and competing policy imperatives.

Advances in numerical algorithms, improvement of computational power and progress in remote sensing have led to the development of global flood models (GFMs), which promise to be a useful tool for large-scale flood risk management. However, performance and reliability of GFMs, especially in data-scarce regions, is still uncertain, as they are difficult to validate. Here we aim at contributing to develop alternative, more flexible, and consistent methods for GFM validation by applying a change detection analysis on synthetic aperture radar (CD-SAR) imagery obtained from the Sentinel-1 imagery, on a cloud-based geospatial analysis platform. The study addresses two main objectives. First, to validate four widely adopted GFMs with flood maps generated through the proposed CD-SAR approach. This exercise was conducted for eight different large river basins on four continents, to account for a diverse range of hydro-climatic environments. Second, to compare CD-SAR-derived flood maps with those obtained from alternative remote sensing sources. These comparative results offer valuable insights into the reliability of CD-SAR data as a validation tool, more specifically how it stacks up against flood maps generated by other remote sensing techniques.

This chapter contributes to assessing the effectiveness of constructed wetlands as flood mitigation measures at catchment scale. The Soil and Water Assessment Tool (SWAT+) was used to model the Råån catchment in southwest Sweden where construction of wetlands has been ongoing since the 1990s. The assessment was based on a paired simulation scenario (with and without wetlands), and performance as nature-based solutions (NbS) was evaluated based on impacts on the downstream river hydrograph (including event-based), descriptive, consequential, and social indicators. The results implied that the flow-regulating capability of the modeled wetlands was directly related to their outflow mechanisms. Because the wetlands seemed to frequently exceed their maximum storage capacity and the excess water was immediately spilled downstream, the wetlands provided limited flood regulation services. However, lack of wetland-specific data motivated a low confidence grade for the indicators. If indicator values are to be useful tools in the future integration of wetlands as NbS, onsite monitoring data and further research are required to assess their impact on upstream-downstream processes.

Mediterranean water-stressed areas face significant challenges from higher temperatures and increasingly severe droughts. We assess the effect of climate change on rainfed barley production in the aridity-prone province of Almería, Spain, using the FAO AquaCrop model. We focus on rainfed barley growth by the mid-century (2041–2070) and end-century (2071–2100) time periods, using three Shared Socio-economic Pathway (SSP)-based scenarios: SSP1-2.6, SSP2-4.5, and SSP5-8.5. Using the paired t-test, Spearman and Pearson correlation coefficient, Root Mean Squared Error, and relative Root Mean Squared Error, we verified AquaCrop’s ability to capture local multi-year trends (9 or more years) using standard barley crop parameters, without local recalibration. Starting with a reference Initial Soil Water Content (ISWC), different soil water contents within barley rooting depth were modelled to account for decreases in soil water availability. We then evaluated the efficiency of different climate adaptation strategies: irrigation, mulching, and changing sowing dates. We show average yield changes of +14% to −44.8% (mid-century) and +12% to −55.1% (end-century), with ISWC being the main factor determining yields. Irrigation increases yields by 21.1%, utilizing just 3% of Almería’s superficial water resources. Mulches improve irrigated yield performances by 6.9% while reducing irrigation needs by 40%. Changing sowing dates does not consistently improve yields. We demonstrate that regardless of the scenario used, climate adaptation of field barley production in Almería should prioritize limiting soil water loss by combining irrigation with mulching. This would enable farmers in Almería’s northern communities to maintain their livelihoods, reducing the province’s reliance on horticulture while continuing to contribute to food security goals. 

Advances in numerical algorithms, improvement of computational power and progress in remote sensing have led to the development of global flood models (GFMs), which promise to be a useful tool for large-scale flood risk management. However, performance and reliability of GFMs, especially in data-scarce regions, is still uncertain, as they are difficult to validate. Here we aim at contributing to develop alternative, more flexible, and consistent methods for GFM validation by applying a change detection analysis on synthetic aperture radar (CD-SAR) imagery obtained from the Sentinel-1 imagery, on a cloud-based geospatial analysis platform. The study addresses two main objectives. First, to validate four widely adopted GFMs with flood maps generated through the proposed CD-SAR approach. This exercise was conducted for eight different large river basins on four continents, to account for a diverse range of hydro-climatic environments. Second, to compare CD-SAR-derived flood maps with those obtained from alternative remote sensing sources. These comparative results offer valuable insights into the reliability of CD-SAR data as a validation tool, more specifically how it stacks up against flood maps generated by other remote sensing techniques. 

Livability of MediterraneanMediterranean cities is highly challenged by the pressure coming from fast-growing urban expansion and climate-induced hazards. To ensure the wellbeing of its inhabitants, cities need to adopt flexible and dynamic approaches to cope, mitigate and/or adapt to these pressures. In this chapter, we first review population and climate challengesChallenges on the Mediterranean Basin, then we summarize how nature-based solutionsNature-based solutions (NBS) (NBS) promise to be a more flexible alternative than traditional gray infrastructure to reduce the effects of climate change-hazards and support sustainable citiesSustainable cities. We focus in particular on the use of NBS to mitigate urban floodingFloodingand heat wavesHeat waves effects, which are particularly relevant for the Mediterranean region. We then address some of the challengesChallenges connected to the implementation of NBS in the MediterraneanMediterranean: lack of evidence to quantify their short and long-term effectiveness; the difficulty of establishing NBS in dense urban cores with high cultural and historical values; the risks of NBSNature-based solutions (NBS) contributing to inequalities; the need for cross-sector, -actor and -level collaborative governance models; the need for NBS that are resilient to present and future changing conditions; the hidden risk of unintended negative effects of NBS. Lastly, we conclude with some final remarks on the need to collect more empirical evidence of the short and long-term performance of NBSNature-based solutions (NBS) and call for a combined effort of natural and social sciences, stakeholders and industry to advance knowledge on NBS behavior, monitor their efficiency and benefits (or disbenefits) on society and follow up on their performance.

This study evaluates the impact of hydroclimate-driven periodic runoff on hydropower operations and production, with a focus on how the forecasted biennial periodicity of runoff time series could affect the efficiency of hydropower generation. Hydrologic stochastic processes are utilized to forecast long-term runoff, and seven hydroclimate scenarios are developed to be input into a production management model, allowing for an analysis of how periodic hydroclimate variations influence hydropower management and output. The results reveal that the biennial alternation between wet and dry years is a key factor affecting hydropower operations in the Dalälven River Basin. Notable differences between wet- and dry-year scenarios were observed in terms of power efficiency, production output, and forecasting accuracy. Operating hydropower systems based on dry-year runoff forecasts in wet years results in a 1.63% decrease in production efficiency and a reduction of 9,104 MWh in power generation. Conversely, applying wet-year forecasts in dry years slightly boosts production efficiency by 0.31% and increases power generation by 7,832 MWh. Scenarios that adhere to biennial periodicity offer the highest forecasting accuracy, particularly when applying dry-year forecasts in dry years in winter and spring, which produce the most precise predictions. In contrast, using dry-year forecasts in wet years results in the lowest forecasting accuracy.

Developing and implementing climate adaptation measures in complex socio-ecological systems can lead to unintended consequences, especially when those systems are undergoing rapid hydro-climatic and socio-economic change. In these dynamic contexts, a systemic approach can make the difference between adaptive and maladaptive outcomes. This paper focuses on the use of climate services, often touted as no-regret solutions, and their potential to generate maladaptation. We explored the interactions between climate services and adaptation/maladaptation across five case studies affected by different types of natural hazards and characterized by a range of hydro-climatic and socio-economic conditions. Using system archetypes, we show how climate services can play a role in both producing and preventing maladaptation. The dynamics explored through system archetypes are: i) “fixes that fail”, where short-sighted solutions fail to address the root causes of a problem; ii) “band aid solutions”, where the benefits brought about in the short-term come at the expenses of delaying long-term adaptive actions; and iii) “success to the successful”, where some groups increasingly benefit from climate services at the expenses of other groups. We demonstrate how these dynamics constitute maladaptive processes, as well as identifying the tools and theories that can be used in this type of assessment. Finally, we provide a framework and recommendations to guide the ex-ante assessment of maladaptation risk when designing and implementing climate services.