Climate change demands a radical rethinking of delta management to ensure long-term safety and sustainability. The Dutch have a long tradition of balancing urban development and water management, using innovative approaches like polders, dikes and windmills to adapt to hydrological challenges. However, large-scale engineering interventions have weakened the connection between flood protection systems and regional water dynamics, emphasizing the need for integrated approaches (National Research Council, 2013). Drawing on the Redesigning Deltas study, this contribution examines how spatial design and civil engineering can address contemporary challenges by adopting a longue durée perspective. This approach aligns historical principles with modern strategies, emphasizing adaptive design, bottom-up governance and the importance of public engagement. Through case studies, it demonstrates how lessons from the past can inform innovative solutions for future delta management, balancing ecological, social and technical considerations.

This final chapter synthesises the explorations within this book on the indeterminate nature of threshold spaces between land and water, revealing their spatial, ecological, and social complexity. Shaped by both natural processes and human interventions, these zones challenge conventional notions of fixed boundaries. Coastal and riverfront areas – often sites of cultural identity, historical memory, and contemporary transformation – are now under mounting pressure from climate change, urbanisation, and infrastructural expansion.

Drawing on a range of case studies, the contributions advocate a shift in planning and design thinking: moving away from rigid delineations towards embracing fuzziness as an operative concept for interpreting, designing, and managing these liminal spaces. This book calls for interdisciplinary approaches that integrate scientific, cultural, and local knowledge to reimagine the adaptation of urban landscapes.

Through a combination of theoretical reflections and practical examples, the chapters in this book develop an essential framework of Fuzziness, offering urban practitioners and researchers new conceptual and operational tools to foster resilience, enhance adaptability, and support sustainable transformation along water bodies.

The demand for a more conscientious and integrated design process in urban infrastructure design arises from the realisation that the environmental crisis can only be addressed by enhancing the resilience of the built environment (Amirzadeh, Sobhaninia, and Sharifi, 2022). Resilience can be achieved through a meticulous design process that seamlessly integrates spatial design and engineering in a smart way <Cutter et al., 2008>. However, since the era of industrialisation, civil engineering and spatial design have evolved into fields with distinct cultures and languages, characterised by protocols and efficient organisation in multidisciplinary cooperation. Meanwhile, the core of urban infrastructure design remains inherently interdisciplinary (Hadfield-Hill, 2020).

Building resilient urban infrastructure that can anticipate the challenges that come with climate change needs an interdisciplinary approach. Deviating from the paradigm of engineering protection can only be done when the spatial context is integrated. Yet, interdisciplinary cooperation between civil engineering and spatial design, fields with very different cultures and languages, has been protocolized to a multidisciplinary collaboration over time. In order to change this Delft University of Technology incorporated interdisciplinary design into its MSc-level education of civil engineers and spatial designers. Taking challenges in Japan, which have been subject to storm surge and tsunami hazards, Albania, the United States, and Ghana, all of which suffer from pluvial, fluvial, and coastal flooding proved solid learning grounds. The interdisciplinary design projects, organised for students from various disciplines, were set up to learn from and perform the hypothetical redesign and reconstruction of areas in flood plains, aiming to increase disaster resilience and liveability.

The participating students were asked to evaluate their projects to be able to assess the effectiveness of the Tohoku interdisciplinary design method and discuss lessons learned for interdisciplinary projects with engineering and design students. The results show that the interdisciplinary project provides engineering students with more broad and practical experience of the sort that has been lacking in the decades since engineering education came to be dominated by academic researchers rather than practitioners. On the other hand, students in architecture and urbanism viewed this opportunity as a chance to apply their already acquired integrative skills in an interdisciplinary setting.

Food and deltaic systems are complex, interlinked systems that are crucial for future sustainable development. This study explores the synergy between these two systems to establish an agroecological framework for delta urbanism. Drawing on political ecology approaches and the infrastructural turn, this study critically revisits food systems to understand how they can be better integrated with hydrological, infrastructural, and urban–rural processes. It also addresses fundamental questions necessary for creating new pathways and redesigning deltaic areas. Second, it examines both past and future models of food equations in relation to the deltaic landscape. Finally, it proposes a spatial framework based on a layered approach that aims to provide an analytical framework for research and design related to deltas and food across various scales and historical timeframes. The operational basis for presenting this methodology is the case of the Mekong River Delta and its rice cultivation territories. Findings emphasize the significance of technological milestones and their spatial implications in shaping resource availability, population growth, and climate change. Further application and operationalization of this framework will provide a deeper understanding of the complex interactions among food production, environmental change, and socioeconomic structures, providing valuable insights into sustainable agricultural practices and climate adaptation.

The collaboration between civil engineering and spatial design disciplines specifically encompasses significant challenges, primarily due to differences in vocabulary, starting with the definition of 'design' itself. In the broadest sense, design is described as a method to find common ground in cases where the measures, problems, and goals are still undefined (Van de Ven et al., 2009). However, most civil engineers are trained to use a linear and optimisation approach to solve problems, while most spatial designers adopt a more explorative, research-by-design approach. Each field employs different paradigms and rationales for problem-solving.

The existence of a long-term past impacts present and future design through the existence of built spaces and long-standing formal or informal institutions. The concept of path dependencies, developed in the political sciences as part of the concept of historical institutionalism (Sorensen 2015, 2017), highlights the role that decisions of the past have on decisions for the future. This impact is particularly significant when it relates to structures that require extensive investment and are designed to last for a long time. The concept of the Longue Durée, introduced by Fernand Braudel (Braudel, 1968), emphasises the relationship between natural conditions and human interaction, creating specific geographies. The concept supports an approach based on understanding earlier typologies and development patterns. It allows for contextualised understanding and avoids uninformed copying and pasting of designs from the past into current cities. It allows designers to identify critical junctures in previous decades and understand the underlying political, social, and cultural contexts of contemporary redevelopment. This influence across time is particularly strong when it has been solidified into concrete or built into extensive and expensive infrastructures, including for water management or ports.

As climate change accelerates, the Netherlands faces increasing challenges from rising sea levels and extreme weather events, leading to floods and droughts. Traditional water management strategies, focused on controlling water through infrastructure such as dikes and barriers, are increasingly questioned due to rising uncertainties. This chapter explores the fuzzy boundary between land and water, focusing on floating urban development as part of a broader paradigm shift towards climate adaptation.

Drawing on recent projects that integrate ecological values, natural processes, and spatial planning into flood defence systems, we argue that a paradigm shift is underway. These initiatives suggest a move away from strictly engineered water management solutions towards more adaptive and multifunctional approaches. Within this changing landscape, we examine whether floating urban development can be part of this transition, addressing its potential and limitations in scaling up as a viable response to climate resilience.

The environmental crisis demands for an interdisciplinary design of urban infrastructure to increase resilience to climate change. Interdisciplinary design is about integration of data, concepts, ambitions and goals by bridging instrumental differences between engineering and spatial design. This paper presents the results of an interdisciplinary design study that deals with persistent flood issues in the Venice lagoon (Italy). The study illustrates how the differences in languages, methods and tools of the disciplines can be overcome by interdisciplinary collaboration directed towards the designing of spatial and technical solutions. Two design proposals are instrumentally described through the lens of the Casco and the Open Building concepts; both advocate the creation of an overarching frame as the basic condition for adaptive design. The paper gives insights on how to cooperate in interdisciplinary design settings in educational environments and builds knowledge on the collaboration between fields that might be relevant also for professional figures.

Coastal dikes have been built for millennia to protect inhabited lands from exceptional high tides and storm events. Currently, many European countries are developing specific programs to integrate the construction of new dikes (or the raising of existing ones) into the built environment to face sea level rising. Technical difficulties in succeeding in this operation are questioning the paradigm of protection for the long term, pointing out the need for alternative strategies of adaptation that are not yet fully explored. This paper elaborates on innovative models to deal with coastal flooding, presenting the results of an interdisciplinary research and design process for the case-study of Southend-on-Sea (UK). Detailed numerical simulations are used to develop a spatial strategy to accommodate water during extreme events, introducing different prototypes of dike designs that include seawalls, enhanced roughness through rock and stepped revetments, as well as vegetation. The overall goal is to push forward the traditional approach of planning water protection infrastructure within the solely field of civil engineering. It elaborates on the integration of the disciplines of spatial design and engineering and presents novel advances in terms of spatial design for the revetment of overtopping dikes.

Driven by population growth and rural migration toward the cities, the demand for affordable housing continues to increase. However, due to the scarcity of urban development space—especially in coastal areas, the supply is limited. As increasing land availability is one of the most effective ways to reduce real estate costs, this interdisciplinary research explores the alternative of urban expansion toward the adjacent marine environment of coastal cities. It focuses on floating residential dwellings from both technological and urban planning perspective, aiming to include the waterfront of coastal cities as viable, sustainable, and affordable alternative for urban development. The research takes on one of the most expensive cities in the world, Tel Aviv-Yafo, as a case study for increasing the supply of affordable housing in addition to vital sustainable future growth in the adjacent marine environment.