From flood-prone to flood-ready: The restoration-adaptation interplay in building resilient multimodal transport networks

Urban transport systems face escalating extreme weather risks due to global climate change. Following UN’s Sustainable Development Goals, building and fostering resilient urban transport systems — understood here not only as resilient against stress and shocks, but also prepared to adapt and transform to a changing environment — is imperative. Such objective faces, among others, two main difficulties: first, the increased complexity of entangled transportation layers, i.e., multimodality, at the face of an event threatening its integrity. Second, the uncertainty of a vast number of travelers, whose reaction to a flooding event is driven by their own motivations and incentives. Here, we introduce an integrated framework to address both challenges, taking as a case study the city of Hamburg in Germany. Our thorough exploration provides insights spanning structural aspects — considering multiple restoration strategies — and behavioral ones—individual and collective transitions in response to floods. Beyond the larger success of one or another network restoration prioritization, results point at the intricate and subtle connection between network structure, traffic dynamics and population’s decisions. Thus, only a fine coordination of network restoration and timely information to guarantee travelers’ awareness can optimize the network functional recovery and foster the resilience against floods of the urban integrated transport system.