Strategic retreat: Balancing risk and societal goals in land-use planning

Many communities worldwide are retreating or preparing to retreat from hazardous areas due to climate change, but where they should relocate to needs careful consideration. The focus to date of "managed retreat," has been on reducing detrimental and undesirable consequences. However, relocation also presents opportunities. Managing retreat should account not only for where people should be moved from but also where they could be moved to, in order to leverage the potential co-benefits and minimise the associated trade-offs. In this research article, we apply a multi-objective spatial optimisation methodology to Christchurch, New Zealand, to address these key research gaps. Our results demonstrate the trade-offs of various retreat strategies, illustrating the risks of pursuing myopic strategies. For instance, we show that a narrow coastal-retreat focus could lead to less accessibility to infrastructure than a more holistic retreat plan and, in fact, be in direct conflict with district zoning plans. However, too much focus on optimising accessibility leaves communities exposed to hazards. Our spatial optimisation approach highlights places for the government to prioritise development while managing retreat and establishes a fundamental tool for stakeholder engagement. Through this process, we present a way for communities to leverage synergistic opportunities for achieving adaptation, sustainability, and access for people, among the other, wide-ranging values of communities. The results make it clear that managed retreat planning needs to actively engage with the complexity of balancing risk exposure with wider societal goals.