Global coastal systems are experiencing an increase in sea level rise (SLR), ocean acidification, and rising ocean temperatures, severely exposing people in low-lying areas to natural hazards and leading to significant environmental and socio-economic damages. European coasts are subjected to an increase in sea levels and an increase in SLR adverse impacts, in particular coastal flooding, saltwater intrusion, coastal erosion, and negative impacts on ecosystems and estuaries, affecting the ability of coasts to adapt to the changing climate.
To facilitate climate action against SLR, the International Panel on Climate Change (IPCC) identifies four types of responses that guide countries in designing effective adaptation strategies: (i) accommodate, (ii) protect, (iii) advance, and (iv) retreat. These represent different approaches for adapting to natural hazards by reducing risks, exposure, and vulnerability in low-lying coastal areas. The European Environment Agency (EEA) has also developed the Key Type of Measures for Adaptation to Climate Change framework to report climate adaptation actions in EEA member countries.
This paper provides a catalogue of 17 coastal adaptation measures implemented in European basins, categorized according to the IPCC and EEA frameworks, to guide their design and implementation. It also presents approaches suitable for supporting coastal adaptation decision-making and addressing uncertainty.
Accommodate Measures
Accommodate measures involve preparing for and responding to coastal hazards. They include a range of responses, such as using early-warning systems, building flood-proof structures, managing groundwater, and implementing insurance and policy instruments.
Flood-proofing and raising buildings is an accommodation measure that involves the use of building techniques with specific designs and materials aimed at reducing flood risk. Dry and wet-proof techniques have shown their effectiveness in reducing impacts of short periods of flooding. For long periods of high water, an appropriate measure is to raise buildings by elevating their height or constructing new ones at higher elevations.
Increasing resilience of critical infrastructure is another accommodate measure that focuses on solutions mainly composed of grey options. Critical infrastructure, such as ports, airports, and power plants, is often located near the coast and at risk of damages and disruption from coastal hazards. Measures to increase resilience include advanced early-warning systems, adaptation plans, and the implementation of climate-risk observatories.
Sustainable groundwater management is an accommodate measure that aims to conserve groundwater reservoirs, limit water use, and optimize water reuse to avoid salinization and increase the adaptive capacity of coastal areas. The Freshwater Delta Programme in the Netherlands is an example of such measures.
Climate risk insurance schemes can play an important role in enhancing coastal resilience and reducing vulnerability by providing financial security to coastal communities and businesses to mitigate the impacts of loss events. Spain has developed specific insurance and reinsurance schemes for risks derived from SLR in coastal areas.
Addressing climate change in credit risk and project finance assessments is an accommodate measure that can mobilize financing for specific adaptation projects through the public and private sectors, international climate funds, and other innovative solutions. Examples include the Netherlands’ Sovereign Green Bond and Spain’s PIMA Adapta Plan.
Protect Measures
Protect measures aim to reduce the risks and impacts of coastal hazards through hard defense and soft defense measures, as well as nature- or ecosystem-based adaptation.
Hard defense for coastal management includes the implementation and upgrade of physical structures such as dams, dikes, levees, groynes, and sea walls. These grey measures have been widely applied for centuries to prevent coastal erosion and flooding. The North Sea coastline of Belgium, the Netherlands, and Germany is protected by dike systems complemented by other measures.
Soft defenses include the restoration and management of coastal ecosystems, such as vegetated systems and biogenic reefs, which can self-adapt to SLR through different mechanisms. Beach and shoreface nourishment is another soft measure that involves the artificial supply of sand to increase coastal sediments and counter erosion.
The Venice MOSE system is an example of a major hard defense infrastructure project that became operational in 2020 to protect the city from high tides and flooding. The system is part of a wider safeguarding approach that includes littoral island defense, adaptation measures in urban settlements, and ecological and morphological restoration of the lagoon.
Advance Measures
Advance measures include strategies such as raising and advancing coastal land, e.g., by creating new raised ports, raising urban embankments, and creating vegetated areas to promote natural land growth.
Grey land reclamation emerges as an advance measure, particularly in high-value urban areas in Europe, where new ports, harbour areas, and safer urban embankments have been created in raised areas. Ecosystem-based advance measures can also include the conservation and restoration of sediment systems, coral barriers, or coastal vegetation.
Retreat Measures
Retreat measures include different adaptation measures, ranging from relocating human activities and infrastructure away from high-risk coastal areas to less vulnerable ones to restoring ecosystems by leaving coastal areas alone.
Planned relocation applies to individuals and critical assets, including the removal of existing hard infrastructure. This measure involves the governance and institutional planning behind the relocation of activities from high-risk areas, land acquisition, and the expropriation of operations.
Managed realignment is an emerging retreat option that entails the landward relocation of coastal defences to allow previously protected areas to restore tidal exchange and coastal habitats. The restored Gyldensteen Coastal Lagoon in Denmark is an example of successful managed realignment in the Baltic Sea basin.
Decision-making Under Uncertainty
Coastal adaptation decision-making is challenging due to the diversity of measures, multiple objectives and trade-offs, diverse interests and social conflicts, long time horizons, and large and deep uncertainties involved.
To support decision-making, a range of analytical tools are available, from relatively straightforward methods like adaptation pathway analysis and multi-criteria analysis to more technically complex approaches such as robust decision-making and real-option analysis.
A critical priority is to set up an iterative policy- and decision-making process that regularly revisits decisions and includes a monitoring framework to identify the need for action in sufficiently early time to allow planning and implementation before negative impacts occur. The dynamic adaptive policy pathways (DAPP) framework is an example that combines these elements.
Trends and Insights Across European Basins
Across European sea basins, a common theme is the shift towards a combination of traditional engineering solutions with soft measures, such as nature-based solutions, integrating local communities into decision-making processes, and emphasizing the importance of continuous monitoring and flexible management strategies.
In the Baltic Sea basin, progress has been made in incorporating SLR projections into spatial planning and land use regulations, upgrading coastal defenses, and restoring coastal wetlands. The North Sea basin countries are implementing different mixes of hard and soft protect measures, with an emphasis on integrated coastal zone management and flexibility for future SLR.
In the Mediterranean Sea basin, key developments include the mainstreaming of SLR information into national adaptation plans, the emergence of insurance as an accommodate measure, and the implementation of soft protect measures such as coastal reforestation and dune restoration. Major urban areas, like Venice and Barcelona, have initiated large-scale adaptation projects.
The Black Sea basin has focused on developing monitoring and early-warning systems and upgrading existing coastal infrastructure. In the Atlantic Ocean basin, countries are implementing a range of measures, with an emerging focus on nature-based solutions and improved spatial planning to reduce risks to coastal development.
Ensuring that these trends lead to appropriate mixes of coastal adaptation measures being found depends on the continued support and involvement of public and private sector stakeholders in effective multi-level governance. Addressing the trade-offs and understanding the effectiveness and feasibility of individual measures in specific contexts remain critical research gaps to advance the field of coastal adaptation.
