Abstract Background Reliable infrastructure is vital for Nordic societies, but they face escalating climate risks. Climate change is increasing magnitude and frequency of floods, storms, and landslides, making adaptive solutions crucial. Methods This review explores Nature-Based Solutions (NbS) for mitigating natural hazards along Nordic linear infrastructure. The motivation of the review comes as result of a preliminary survey conducted among to the main infrastructure managers in the Fennoscandian peninsula. The objective was to pinpoint the natural hazards that pose greatest concern under future climate scenarios, as well as to understand which specific information is needed to adopt NbS Results Floods, erosion, landslides and rockfalls emerged as primary hazards of concern for the infrastructure owners, hence the review process was focused only on NbS aimed at mitigating the effects of these specific hazards. A total of 78 documents were identified from the review process and were integrated with examples and case studies from other relevant on-going and past projects. Despite only a few of the NbS identified in these documents were directly implemented for linear infrastructure such as roads and railways, and none dealing with electric grids, several NbS were identified to have a potential for implementation for Nordic linear infrastructure. A list of NbS options, not all implemented along linear infrastructure but with potential for it, is provided. This list is meant to serve as “vade mecum” for a quick and easy access to NbS as mitigation options for linear infrastructure managers in the Nordic Countries. The NbS are classified in green, blue, green/blue and hybrid approaches, and supported by examples of case studies both in the Nordic Countries as well as countries having similar climates. Conclusions This review underlines the challenges and opportunities of adopting NbS. Challenges such as the lack of expertise, space and climate constraints, and path dependency on adoption of traditional infrastructure must be addressed to mainstream NbS. The review highlights the importance of standardization, European guidelines, and technical manuals in promoting NbS adoption among infrastructure managers, as well as the necessity of accounting for the wider co-benefits of NbS, including carbon sequestration, biodiversity and ecosystem services. This paper contributes to the understanding of NbS as potential natural hazards mitigation options for Nordic infrastructure networks in the face of evolving climate risks, providing valuable insights for infrastructure managers and policymakers alike.

As the sea level rises and the frequency of intense rains increase, so does the need for climate adaptation. Planning for a successive development of society away from current and future flood prone areas to give room for water is not seen as an alternative in Sweden today, although it could be a strategy that creates long-term security.In this study, we investigated Swedish public authorities' perceptions of planned retreat and flexible land use. This was done through an online survey and interviews directed to officials directly involved in climate adaptation work, at municipalities, County Administration Boards (CABs), Regions, national authorities (NAs), and industry organizations (IOs). The responses were analyzed through the lens of a windows of opportunity approach. The study indicates that the extent to which climate scenarios are used and how far into the future the planning horizon extends in the practical work, varies between governance level which also have impact on the perspectives on planned retreat. The openness for planned retreat and flexible strategies seemed to differ slightly between governance levels in an ascending scale from regions, IOs / NAs, municipalities, to CABs. The survey has generated insights from a large number of respondents at different governance levels sharing their perceptions of retreat and adaptation in Sweden as a main contribution of this work.Difficulties to deal with uncertainties in climate scenarios and considering long-term perspectives were identified as some reasons that close the window for planned retreat. Enabling a flexible use of the land that will gradually become more exposed to flooding and sea level rise could be an intermediate step towards retreat. This would be a way to reframe a closed window of opportunity and begin the process of turning it into something transformative. It could be where the short- and long-term planning meet and a way to reframe our way of thinking about how we live and reside in dynamic waterfront areas, and perhaps lead to a more transformative, safe, and sustainable society for future generations.

Hydrodynamic forces from ships operating in sheltered, confined fairways can result in increased wave impact and sediment transport leading to loss of land and habitats. Nature-based solutions (NBS) offer the potential to mitigate ship-induced erosion and increase biodiversity and ecosystem services. The aim of this study is to evaluate the performance of NBS in a sheltered, confined fairway located in a cold, temperate region. The case study presents the results of a 2.5-year study of the morphologic response at two sites where NBS was implemented to mitigate bluff erosion and at one site where NBS was implemented to mitigate the retreat of a reed belt. Moreover, a qualitative assessment was made of the vegetation development at the sites. The results showed that fine sediments with planted vegetation could not withstand the hydrodynamic forces induced by the ships. However, by adding sills as stabilizing structures, the forces were sufficiently attenuated for the vegetation to establish. The vegetation, which reduced the ship-generated waves and currents, was especially important during high water-level events when the energy dissipation by the sill decreased. Moreover, a small-scale nourishment was successfully applied to mitigate bluff erosion without negatively affecting sediment supply to an adjacent sandy beach. This study demonstrates that NBS can be implemented to retain erodible sediment and favour vegetation growth in fairways experiencing primary and secondary waves produced by large, ocean-going ships.

Many climate adaptation options currently being discussed in Sweden to meet the challenge of surging seas and inland flooding advocate holding the line through various hard and soft measures to stabilize the shoreline, while managed retreat is neither considered as feasible option nor has it been explicitly researched in Sweden. However, failure to consider future flooding from climate change in municipal planning may have dangerous and costly consequences when the water does come. We suggest that managed retreat practices are challenging in Sweden, not only due to public opinions but also because of a deficit of uptake of territorial knowledge by decision-makers and difficulties in realizing flexible planning options of the shoreline. A territorial governance framework was used as a heuristic to explore the challenges to managed retreat in four urban case studies (three municipalities and one county) representing different territorial, hydrological and oceanographic environments. This was done through a series of participatory stakeholder workshops. The analysis using a territorial governance framework based on dimensions of coordination, integration, mobilization, adaptation and realization presents variations in how managed retreat barriers and opportunities are perceived among case study sites, mainly due to the differing territorial or place-based challenges. The results also indicate common challenges regardless of the case study site, including coordination challenges and unclear responsibility, the need for integrated means of addressing goal conflicts and being able to adapt flexibly to existing regulations and plans. Yet rethinking how managed retreat could boost community resilience and help to implement long-term visions was seen as a way to deal with some of the territorial challenges.

Sea level rise poses profound challenges within current municipal and regional governance since it requires unusually long planning horizons, is surrounded by great uncertainties, and gives rise to novel ethical challenges. Adaptation to climate change is fundamentally an ethical issue because the aim of any proposed adaptation measure is to protect that which is valued in society. One of the most salient ethical issues discussed in the adaptation literature relates to the distribution of climate related risks, vulnerabilities and benefits across populations and over time. Raising sea-walls is typically associated with high costs and potentially negative ecological impacts as well as substantial equity concerns; managed retreat or realignment often causes problems related to property rights; and migration out of low-lying areas can involve the loss of sense and cultural identity and impact on receiving communities. How can the soft and ethical dimensions of rising mean sea levels be characterized and how can their consequences be mapped? To help municipalities to understand the values and ethics attached to measures to deal with long-term rising sea levels in southern Sweden, we are developing a methodology of soft or ethical values to complement to GIS-mapping of coastal vulnerability based on coastal characteristics and socio-economic factors. Rather than determining these values a priori, they are being discerned through workshops with relevant stakeholders and in interviews with citizens residing in and utilizing the coastal areas. The methodology attempts to determine the place-based of values within coastal communities with a focus on “whose” values, “what” values, and the long-term or short-term nature of values. It builds on an analytical framework developed to acquire information on the behavior, knowledge, perception and feelings of people living, working and enjoying the coastal areas. In turn this stakeholder-based information is used to co-create “story maps” as tools to communicate complicated vulnerability analyses, highlight the ethical dimensions of various adaptation measures, raise awareness and aid decisionmakers in taking uncomfortable decisions to “wicked” planning problems around the negative effects of sea level rise, coastal erosion and urban flooding. This paper presents the methodological development of the task as well as the results the study in four Swedish municipalities. The representation of the “soft” and ethical values provides an opportunity to help clarify these values to policymakers and increase resilience to rising sea levels.

AbstractThe County Administrative Boards in Skåne and Halland, together with the Swedish Geotechnical Institute (SGI), and Swedish Geological Survey (SGU), have taken the initiative to start a Regional Coastal Cooperation. Both counties’ municipalities and individuals are currently facing problems managing rising sea levels, erosion and flooding.Regional cooperation is important for Skåne and Halland as they are the two counties in southern Sweden that are most likely to be exposed to the combined effects of rising sea levels, flooding and erosion. Strategic and coordinated efforts at local level are needed to deal with these challenges in coastal areas, where guidance and support are also provided from regional and national levels. Today's governance system where the responsibility for dealing with these challenges falls on municipalities and individual home owners, presents difficulties in solving complex issues. Various actors feel that they are affected in a way that is not fair. Implementing appropriate measures requires extensive coordination, collaboration, a clear division of responsibilities and financial resources. Regional Coastal Cooperation aims, among other things, to inform national decision-makers in close dialogue with the coastal municipalities in Skåne and Halland that there is a need to strengthen the state's responsibility for these issues.Regional Coastal Cooperation also to highlights the need to develop knowledge and planning in order to deal with the difficult issues associated with rising sea level which may affect the development, infrastructure and other values ​​on the coast. Today, there is no comprehensive information on how coastal processes affect different coastal sections in Skåne and Halland. Knowledge about different types of measures and how well they work also needs to be increased. Increased knowledge and consensus are necessary to achieve measures that involve sustainable development in accordance with Agenda 2030 and the global goals.The overall goal of Regional Coastal Cooperation is to find concrete solutions to address the challenges posed by rising sea levels, erosion and flooding in coastal areas in Skåne and Halland in ways that are environmentally, economically and socially sustainable.In this presentation, we discuss the challenges and potentials of how five identified project groups within Regional Coastal Cooperation project work to implement solutions in coastal areas. Thus, we present how coastal municipalities and the property owners concerned gain knowledge of coastal processes, potential risks and possible measures. We evaluate how coastal municipalities develop and implement strategies for planning and managing the coast that ensure long-term sustainable solutions; manage erosion and flood on the basis of good knowledge, long-term visibility, flexibility, transparency and a holistic perspective. And we highlight how Regional Coastal Cooperation works to ensure that there is a sustainable and fair distribution of responsibilities and financing model for the undertaken measures. Finally, we assess the need for continued and strengthened cooperation in these coastal regions.

This study focuses on the sediment transport by ship-generated waves in restricted waterways. Two data sets from Göta River in Sweden, an important shipping lane on the Swedish west coast, were analyzed in detail to determine the impact of ship waves, namely (1) continuous recordings of turbidity at seven stations along the river with 1-min resolution; and (2) dedicated field campaigns to measure water level and turbidity during ship passages. Measured turbidity was related to the suspended sediment concentration (SSC) and used as a proxy for the sediment transport. Several existing formulas were tested to evaluate their capability to predict both the primary and secondary waves, and the PIANC formula yielded the overall best agreement for the secondary (divergent) waves and a relationship based on the vessel sinkage for the primary (drawdown) waves. The turbidity (SSC) was found to depend primarily on the drawdown wave properties and empirical equations were derived to estimate the maximum turbidity during a ship passage at the study site. Finally, the advection-diffusion equation was used to model the impact of the ship on the sediment transport by describing it as moving source. The fit of an analytical solution to turbidity measurements indicated the potential for this type of rather simple model.

In a changing climate, coastal areas are often the most vulnerable areas. They are often highly populated and infrastructure such as buildings, industry, roads and railroads is also typically abundant. Coastal areas are therefore vulnerable for climate change induced threats, such as e.g. erosion, flooding, and cyclones. The vulnerability method presented in this paper is focusing on erosion, and the idea is to develop a semi-automatic GIS-based vulnerability mapping method, that presents the vulnerability on an illustrative and colored map. The method will be used to create vulnerability maps for Swedish municipalities, which are easy to use in their planning process.