Cities are often described as resilient when they can absorb a shock and return to normal. But a new study in npj Urban Sustainability argues that this familiar definition may be too narrow for the urban world of the future. In “Sustained resilience as a unifying property of cities and the built environment,” researchers S.A. Mitoulis, N. Kopiika, R. Di Bari and colleagues present sustained resilience as a broader principle that connects cities, infrastructure and the buildings within them. The idea shifts attention away from a single dramatic recovery after a flood, earthquake, heatwave or economic crisis and toward the ability of urban systems to keep functioning, adapting and improving through repeated disruption. That distinction is becoming increasingly important as cities face overlapping pressures rather than isolated emergencies. Extreme weather, aging infrastructure, rapid population growth, energy insecurity and social inequality can interact in ways that turn one disturbance into a chain reaction. A resilient city, under this view, is not simply one that survives a crisis. It is one that continues to provide essential services while learning from stress and preparing for the next challenge.
The concept of sustained resilience is especially relevant because the built environment is not a collection of independent objects. Buildings, bridges, roads, drainage networks, power systems, water supplies, hospitals and communication infrastructure operate as interconnected networks. When one component fails, the consequences can spread well beyond the original point of damage. A flooded transport tunnel can delay emergency response; a power outage can disable water pumps; a damaged hospital can overwhelm facilities in neighboring districts. Engineers often describe these relationships using concepts such as interdependency, redundancy and cascading failure. Interdependency means that one system relies on another, while redundancy refers to the presence of alternative components or routes that can maintain service when part of a network fails. Sustained resilience brings these technical ideas together with social and institutional capacity, asking whether the entire urban system can continue operating over long periods of stress rather than merely withstand a single event.
This approach also challenges the idea that resilience has a fixed endpoint. In a conventional disaster-recovery model, the goal is often represented as a return to a previous condition, sometimes called the baseline state. That model can be useful for measuring physical damage, but it may conceal important weaknesses. Returning quickly to a vulnerable arrangement can simply restore the conditions that produced the original risk. A city rebuilt in the same floodplain, with the same drainage limitations and the same social inequalities, may appear recovered while remaining exposed. Sustained resilience instead treats recovery as a dynamic process. The desired outcome may be different from the pre-disaster state: safer buildings, more flexible public services, lower energy demand, improved accessibility and stronger community networks. In technical terms, resilience becomes a capacity for maintaining critical functions and adjusting system performance as environmental, social and economic conditions change.
One of the study’s most significant implications is that resilience cannot be measured only by the strength of individual structures. A building may be designed to resist a specified earthquake intensity or wind speed, yet the surrounding community may still become inaccessible if roads, utilities or emergency services fail. Similarly, a flood-resistant structure may offer limited protection if residents cannot evacuate, afford repairs or return to work. This means that structural engineering must be connected to urban planning, environmental science, public health and social policy. Performance-based design can help engineers estimate how a building will behave under different hazard scenarios, including whether it remains safe, repairable or operational. At the city scale, however, performance also depends on recovery time, service continuity and the distribution of risk. Sustained resilience therefore encourages a multi-scale assessment, from materials and structural components to neighborhoods, infrastructure corridors and metropolitan regions.
The framework is particularly powerful in the context of climate change, which is altering the frequency, intensity and geographic distribution of hazards. Heatwaves can degrade road surfaces, increase electricity demand and threaten human health at the same time. Heavy rainfall can overwhelm drainage systems that were designed using historical climate records no longer representative of present conditions. Coastal cities face the combined effects of sea-level rise, storm surges, saltwater intrusion and land subsidence. These pressures are not necessarily temporary. They can create chronic stress that gradually reduces the performance of buildings and infrastructure even in the absence of a headline-making disaster. Sustained resilience asks whether urban systems can operate under this continuous load, whether maintenance and adaptation are funded before failure occurs, and whether design standards can evolve as new evidence emerges. The emphasis is therefore not only on emergency response, but also on monitoring, preventive investment and long-term adaptation.
The researchers’ unifying perspective also highlights the role of time. Materials deteriorate, populations move, technologies change and land-use patterns evolve. A resilient design that performs well today may become inadequate decades later if it cannot be modified or maintained. This is why adaptability is a central technical feature of sustained resilience. Adaptable buildings can be reconfigured for new uses, strengthened without complete demolition or equipped with systems that respond to changing conditions. Infrastructure can be designed with modular components, distributed energy generation, multiple water sources or flexible capacity. Digital tools, including remote sensing, structural-health monitoring and urban digital twins, can help authorities detect damage and model possible interventions. Yet technology alone cannot guarantee resilience. Data must be interpreted, maintenance must be carried out and decisions must be coordinated across agencies. The framework places equal importance on physical design and the governance systems that keep urban assets functional throughout their life cycle.
That governance dimension may be crucial because resilience is unevenly distributed. Wealthier districts often have stronger buildings, better drainage, more reliable utilities and greater access to insurance and emergency assistance. Vulnerable communities may live in areas exposed to flooding, landslides, extreme heat or industrial hazards while having fewer resources to recover. If resilience investments focus only on protecting valuable infrastructure or central business districts, they may reduce measurable economic losses without reducing human suffering. A sustained approach requires asking who benefits from adaptation, who bears the cost and which services are essential for people with limited mobility, insecure housing or restricted access to information. Social resilience can include trusted local organizations, inclusive emergency planning and the ability of residents to participate in decisions about rebuilding. These factors are not secondary to engineering performance. They influence whether technical systems are used, maintained and accessible when a crisis arrives.
The study’s message arrives as urban authorities worldwide search for ways to manage risk without replacing entire cities. The most effective strategies may combine gradual interventions rather than rely on one large protective project. Updating building codes, restoring wetlands, improving stormwater storage, reinforcing critical structures, expanding shaded public space and decentralizing energy systems can work together to reduce exposure and preserve essential functions. Nature-based solutions can complement conventional infrastructure by slowing runoff, cooling neighborhoods and protecting coastal edges, while distributed systems can prevent a single failure from disabling an entire network. Such measures require coordination across planning periods that rarely align with political cycles. They also require metrics that capture more than construction output. Authorities may need to track service continuity, recovery time, maintenance quality, adaptive capacity and the ability of different population groups to withstand disruption. Sustained resilience turns these long-term considerations into a central measure of urban performance.
The idea may also change how future cities define success. Instead of asking whether a structure was built to a particular standard or whether a damaged district has been restored, planners could ask whether the urban system is becoming less fragile over time. That means identifying critical functions, mapping dependencies, testing failure scenarios and designing pathways for safe transformation. Scenario analysis can reveal how simultaneous hazards might interact, while network models can estimate how disruption in one sector affects others. Life-cycle assessment can compare the environmental and economic consequences of repair, replacement and adaptation. Importantly, the approach recognizes that resilience is not a permanent label. It must be renewed through inspection, investment, learning and public participation. Cities that maintain resilience over decades will likely be those capable of treating every disruption as information: evidence of where systems are strong, where hidden dependencies exist and where future design must improve. The study presents sustained resilience not as a single technology or policy, but as a shared property emerging from the continuous interaction of buildings, infrastructure, ecosystems and communities.
As climate and urban risks accelerate, this broader definition could become one of the most consequential ideas in city design. A seawall, a stronger bridge or a heat-resistant building may protect people from a specific threat, but no isolated intervention can secure an interconnected metropolis facing multiple forms of stress. Sustained resilience offers a way to evaluate whether cities can preserve essential services, adapt without deepening inequality and recover without reproducing the vulnerabilities that caused damage in the first place. The concept links structural reliability with social capacity, environmental performance and institutional learning. It suggests that the future of urban safety will depend less on creating systems that never fail than on creating systems that fail safely, recover intelligently and become better prepared after each shock. In that sense, resilience is not a destination reached when construction ends. It is an ongoing urban capability—one that must be designed into the built environment, supported by governance and continuously tested by reality.
Subject of Research: Sustained resilience in cities and the built environment
Article Title: Sustained resilience as a unifying property of cities and the built environment
Article References: Mitoulis, SA., Kopiika, N., Di Bari, R. et al. “Sustained resilience as a unifying property of cities and the built environment.” npj Urban Sustainability (2026). https://doi.org/10.1038/s42949-026-00457-3
Image Credits: AI Generated
DOI: 10.1038/s42949-026-00457-3
Keywords: Urban resilience, built environment, climate adaptation, infrastructure, disaster risk reduction, sustainable cities, resilient buildings, urban systems, cascading failures, sustainability
