From coping to resilience: The role of managed retreat in highly developed coastal regions of New Zealand

Sea-level rise is an inevitable consequence of a warming world and will continue long after global average temperatures may have been stabilized. Nonetheless, significant uncertainty remains about the rate and magnitude of this rise over the coming decades to centuries, in particular, the contribution from polar ice sheets. Most responses to sea-level rise consist of coping mechanisms, such as raising minimum floor levels applied to existing developments, or preventative measures, such as coastal hazard lines applied to greenfield developments. However, the effectiveness of such responses, if they are employed in a static way and not supported by additional policies that recognize the dynamic nature of coastal hazards, is expected to diminish as sea level continues to increase in the long term (beyond 2100) and may exceed process model-based projections even within the twenty-first century. Here, we aim to advance the discussion of managed retreat as an additional tool to promote the resilience of highly developed coastal regions and to increase the flexibility of local response options. We provide an overview of policies to support managed retreat that link with different socioeconomic contexts, community preferences, and timescales for implementation. We explore the potential implications of these alternative approaches for two case study sites in New Zealand and highlight the technical and institutional elements that would support the implementation of managed retreat in practice. We conclude that, given the risk from and uncertainties about sea-level rise, as well as the long time frames to implement managed retreat, further active development of policy tools and the information base required for managed retreat would contribute to the resilience of coastal communities.