Exploring feedbacks between city development and adaptation responses to rising sea levels

Human-induced global warming has led to rising sea levels and more severe weather events. Under a high sea level rise scenario, sea levels will likely rise above 1m by 2100 and will inevitably continue to rise for centuries despite efforts to stop global warming. Coastal regions face increased exposure, reinforced by continuous urban development in low-lying areas. Urban expansion in flood-prone areas has incentivized the implementation of “hard” protection measures such as dikes. Despite entailing high capital costs and stimulating increased flood exposure, protection strategies have prevailed along developed coastlines of Europe.

It has become imperative to recognize that responses designed to reduce exposure and vulnerabilities often fall prey to being “fixes that fail” or “shifting the burden.” These pitfalls may stem from a failure to formulate integrated visions based on systems thinking, leading to unsustainable or maladaptive adaptation pathways. Despite the widely held view that adaptation should be an integral aspect of sustainable urban development, practical examples show persistent shortcomings in urban planning practices and flood-risk adaptation.

The main objective of this Ph.D. project was to explore the interplay of coastal city development and adaptation responses to rising sea levels to inform robust and sustainable adaptation pathways of coastal cities. The Ph.D. aimed to challenge current biases in adaptation planning to avoid adverse consequences. Specifically, the project explored whether and how planning processes of city development and coastal adaptation consider each other and the unintended consequences of coastal adaptation strategies arising from feedback mechanisms in the coastal urban system.

The project inherently required a multidisciplinary approach involving different research fields (i.a., urban planning, hydrology, architecture, social science) and methodological approaches (i.e., quantitative and qualitative). Methodological steps applied in the studies included literature reviews, workshops, systems analysis, flood risk analyses, and economic analyses. The project took a point of departure in an extensive literature review of assessment frameworks for sustainable urban development and coastal adaptation to elicit potential differences in planning objectives applied in science and practice. It became apparent that there is a remarkable lack of overlap between assessment frameworks for sustainable urban development and coastal adaptation. We argued that an integrated vision and assessment of planning processes must be pursued to avoid trade-offs and harvest synergies between the planning domains.

As a step toward closing this gap, we developed a conceptual systems model mapping the complex interactions of coastal urban processes across dimensions of environment, society, economy, and governance. We analyzed three generic adaptation strategies (i.e., protection, accommodation, and planned relocation) and their impact on different city functions driven by feedbacks between urban processes. We identified seven central feedback mechanisms - some well-documented and others undocumented in literature - primarily governed by four critical drivers, i.e., flood risk perception, institutional capacity, trust in public institutions, and economic capacity.

The interplay between urban development in flood risk areas, flood risk, protection cost, and, on the other hand, economic gain from urban development was found to be particularly important. We developed a framework to quantitatively capture this interplay. We applied the framework to a medium-sized Danish coastal city to explore the long-term economic consequences for local communities under varying local conditions, including landscapes, socioeconomic performance, population, and rising sea levels. The results showed that coastal protection strategies can be robust in some cities while being risky in others, even when traditional cost-benefit analysis favors protection. The framework offers a new, stakeholder-oriented perspective by illustrating the local economic consequences of protection strategies.

This Ph.D. thesis has summarized efforts to shed light on the complex interactions between city development and adaptation to rising sea levels to tackle the adverse consequences of siloed approaches. The findings contribute to existing literature highlighting the need for a systems lens on adaptation planning processes. The proposed frameworks can be used to foster robust and holistic decision-making toward more sustainable adaptation pathways. Through their simple and generic characteristics, developed frameworks become comprehensible for stakeholders from different disciplinary fields, including those with limited modeling and technical skills. The frameworks constitute a stepping stone for future context-specific applications and model refinements.