To reduce current and future coastal flood risk, it is critical to better understand how adaptation measures, including nature-based solutions, can reduce that risk. Globally, hybrid coastal defenses, including a combination of coastal vegetation, such as salt marshes and mangroves, with a dike or sea wall, have been highlighted as a promising adaptation measure. Here, we present a global-scale assessment of the potential risk reduction from mangrove restoration in combination with foreshore dike systems under scenarios of climate and socioeconomic change. We provide a quantitative assessment of the benefits in terms of reduced economic damage, exposed population, and poverty exposure. We evaluate mangrove restoration fronting dikes by accounting for wave–vegetation interaction. If mangrove foreshore dike systems were established along coastlines susceptible to flooding, restoration could potentially reduce expected annual damage by US$800 million and reduce expected affected population by 140,000 annually. These values increase under future projections. Our benefit–cost analysis finds mangrove restoration economically viable for about half of the subnational regions assessed (85 to 105 out of 208). At the global scale, the benefit–cost ratio under future conditions ranges from 3 to 6, with a net present value between US$44 billion and US$125 billion. Because absolute risk values and benefit–cost analysis do not differentiate between relative wealth impacts, we also estimated restoration impacts across different wealth levels. We show that restoring mangroves disproportionately benefits people with lower incomes, as they are often more exposed to coastal flooding and located in areas suitable for mangrove restoration. As such, mangrove restoration in low- and middle-income countries could contribute to the resilience of people in poverty.

Abstract
We perform the first global analysis of storm surge seasonality using surge data from a global hydrodynamic model with full coverage of coastal areas, providing valuable insights for regions not represented in alternative observational data sources. We apply directional statistics based on the mixture model of the von Mises‐Fisher distribution to identify surge seasons and their characteristics. Results reveal that nearly half of the global coastal stations, predominantly in tropical and subtropical regions, either lack a distinct surge season or experience heightened surge activity across multiple periods. Furthermore, the seasonality of storm surges follows a consistent large‐scale spatial pattern tied to regional atmospheric variables. Spatial variability in the length of surge seasons is minimal in regions with bimodal surge seasons; however, the variability of surge peaks differs. Lastly, the seasonal distribution of storm surges differs regionally due to the underlying storm regime. These results provide valuable insights into the seasonality of storm surges on a global scale, which is useful for coastal risk management.

Plain Language Summary
Storm surges, the abrupt rise in sea levels above tidal elevations during a storm, are among the most devastating causes of coastal flooding globally. However, they are influenced by seasonal variations in atmospheric processes, which can amplify their peaks. In this study, we analyzed when these peaks typically occur and how the seasons vary spatially over a consistent period globally. By using surge data from a global hydrodynamic model with comprehensive geographical coverage, we provide insights for regions that lack observations from alternative data sources such as tide gauges. We show that the seasonality of surge peaks is not confined to a single well‐defined season globally. Some regions lack clear seasons, while others have well‐defined seasons with varying numbers. This means that some regions have more pronounced seasonal cycles than others. Despite this variation, the seasonal patterns are regionally coherent and are tied to underlying atmospheric patterns. Understanding these seasonal patterns could help improve coastal management plans, especially in places with extended surge risk windows

The unprecedented resolution of a new 2D modeling approach greatly improves our understanding of how mangroves reduce flood risk.

Due to rising sea levels and projected socio-economic change, global coastal flood risk is expected to increase in the future. To reduce this increase in risk, one option is to reduce the probability or magnitude of the hazard through the implementation of structural, Nature-based or hybrid adaptation measures. Nature-based Solutions in coastal areas have the potential to reduce impacts of climate change and can provide a more sustainable and cost-effective alternative to structural measures. In this paper, we present the first global scale assessment of the benefits of conserving foreshore vegetation as a means of adaptation to future projections of change in coastal flood risk. In doing so, we extend the current knowledge on the economic feasibility of implementing global scale Nature-based Solutions. We show that globally foreshore vegetation can contribute to a large decrease in both absolute and relative flood risk (13% of present-day and 8.5% of future conditions in 2080 of global flood risk). Although this study gives a first proxy of the flood risk reduction benefits of conserving foreshore vegetation at the global scale, it shows promising results for including Nature-based and hybrid adaptation measures in coastal adaptation schemes.

Coastal flood hazard and exposure are expected to increase over the course of the 21st century, leading to increased coastal flood risk. In order to limit the increase in future risk, or even reduce coastal flood risk, adaptation is necessary. Here, we present a framework to evaluate the future benefits and costs of structural protection measures at the global scale, which accounts for the influence of different flood risk drivers (namely sea-level rise, subsidence, and socioeconomic change). Globally, we find that the estimated expected annual damage (EAD) increases by a factor of 150 between 2010 and 2080 if we assume that no adaptation takes place. We find that 15 countries account for approximately 90 % of this increase. We then explore four different adaptation objectives and find that they all show high potential in cost-effectively reducing (future) coastal flood risk at the global scale. Attributing the total costs for optimal protection standards, we find that sea-level rise contributes the most to the total costs of adaptation. However, the other drivers also play an important role. The results of this study can be used to highlight potential savings through adaptation at the global scale.

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