Spatial Climate Change Adaptation using Dynamic Adaptive Policy Pathways (DAPP): Wait, Protect or Retreat?

This thesis examines the development of spatially explicit adaptation pathways for a gravity-based drainage system under multi-hazard risk across three connected coastal archetypes. The archetypes are based on a case study in Petone/Alicetown, a low-lying coastal area north of Wellington, New Zealand, affected by both sea-level rise and increasing precipitation.

Due to different hazard contributions over time, adaptation timelines diverge across archetypes, leading to spatiotemporal differences in when adaptation pathways are triggered. These differences affect both adaptation timing but also shapes trade-offs for different pathways as risk evolves. Therefore, adaptation responses cannot be considered in isolation. Interactions occur that can provide synergies or conflicts leading to dependencies or changed conditions for adaptation.

The scalability and transferability of Dynamic Adaptive Policy Pathways (DAPP) is explored drawing on evidence from case studies in Denmark. It assesses how DAPP is currently implemented and whether it is ready to support long-term, scalable adaptation planning. Combined, these two parts address the overarching research question:

How can spatially explicit, multi-hazard adaptation pathways be developed to stage adaptation responses over time, and what are the implications for their scalability and monitoring?

Adaptation pathways aim to keep options open, but even at the spatial scale of Petone/ Alicetown, spatiotemporal dependencies and competing objectives may require earlier decisions than anticipated. Risk components in adjacent archetypes interact through archetype-specific interventions and must align with the timing of adaptation responses. Identifying local interactions and dependencies can help unbundle complexity, allowing pathways to be tailored to the local decision context. If systemic connections are known, early climate impacts in one archetype can signal risk changes across archetypes based on known physical interrelations and interactions between the risk determinants in the system. Cross-archetype monitoring, particularly where service failures will emerge early, can reveal hidden risk changes through a physical cross-understanding of the system. 

The spatial staging identifies timing conflicts for transformative adaptation options, such as managed retreat, and evaluates how decision points change depending on different adaptation timelines. By spatially staging the managed retreat pre-emptively, upcoming changes in service levels of critical infrastructure, such as drainage networks, can be signalled in advance. Pathways need to be tailored to reflect these changes as the adaptation responses are not triggered equally 

across time and space. This spatiotemporal ‘lag’ in adaptation decision-making buys time and therefore provides opportunities, especially in a long-term strategy that aligns different systems. 

Visualizing how different threshold assumptions dictate the triggering of adaptation responses can help decision makers evaluate pathways over time. It can quantitatively show the consequences of different definitions of what constitutes a threshold. By exploring what is considered a threshold, its implications over time can be explored for different scenarios. If translated into actionable monitoring arrangements, spatially explicit pathways can be embedded within a spatially extended DAPP framework. However, to make this operational, governance, funding and monitoring need to be better coordinated to capture the benefits as complexity increases across changing objectives, spatial scales, and decision levels.