People have long been drawn to the coast by the availability of transport links, amenity value and access to marine resources. Being located on the coast has many benefits, but also exposes people and assets to a range of hazards, such as storm surges. Climate change induced sea-level rise will act as a risk multiplier, affecting the world’s coasts by increasing flood and erosion risks, and potentially fully inundating some areas. As risks increase, so will the associated economic and human costs from extreme events and slow-onset changes. New modelling projects that under a high-end sea-level rise scenario, residual damage costs could be between USD 1.7 trillion and USD 5.5 trillion over the 21st century.

Existing institutional arrangements will be put under pressure by increasing risks. For example, in countries where flood insurance is provided on a commercial basis, coverage may become unaffordable or unattainable as premiums increase in line with risks or insurers withdraw from markets. National governments may also be exposed to increasing contingent liabilities given their role in providing relief and compensation for uninsured losses after they happen. Increased exposure and hazards will make it more expensive to protect all properties to a given standard, which will have financial implications for different levels of government, as well as for individuals. Adaptation options, such as protect, accommodate, retreat can reduce the economic and human costs of sea-level rise, and are considered economically rational for most developed coastlines. A combination of these options will be required to address future risks. However, policy misalignments and other barriers can hinder the implementation of cost-effective responses or lead to choices that prove maladaptive over time.

In order to gauge progress and gain insights from countries’ coastal adaptation efforts, this study reviews member countries’ adaptation plans. While in most OECD countries local governments implement measures that directly manage coastal risks, the enabling framework is set at the national level. The analysis reveals that the implementation of measures to support adaptation to sea-level rise is generally at an early stage, despite the trends of increasing losses. The results additionally find that while many countries are increasing investments in information services, there has been less action in considering regulation, economic instruments, funding and operational monitoring evaluation frameworks.

Four case studies (Canada, Germany, New Zealand and the United Kingdom), provide in‑depth examples of the challenges and success factors of coastal adaptation strategies under different institutional contexts. Drawing on these case studies, this report puts forward four principles of a policy framework for coastal adaptation that is equipped to meet the challenges described above, which should be considered by national governments as they further develop their adaptation plans:

• engage stakeholders early and substantively

• plan for the future and prevent lock-in to unsustainable pathways

• align actors’ responsibilities, resources and incentives

• explicitly consider distributional and equity implications of policies.

There is robust evidence and a compelling case for further action to address the consequences of sea-level rise. While not all coastal risks can be avoided, well-prepared coastal communities will be better able to adjust to new conditions, at lower cost, and rapidly bounce back from disasters when they do occur.