Strategies, tools and rules for the regeneration of coastal urban systems. The case study of the Teizan Canal in the Sendai plain, Tōhoku, Japan

Climate change calls for an urgent revision of urban planning tools, particularly in coastal urban systems — fragile territories increasingly exposed to both chronic and acute phenomena such as tsunamis, storm surges, coastal erosion and sea level rise (Mariano et al., 2021). Developing integrated and adaptive strategies is therefore crucial to support the transition toward antifragile territorial configurations (Carter et al., 2024). This study examines the adaptive planning policies and instruments implemented in Japan after the 2011 tsunami, focusing on the Teizan Canal (Tōhoku region), a historic hydraulic infrastructure that demonstrated significant wave-mitigation capacity and subsequently became a key driver of ecological restoration and urban regeneration. Its role illustrates the potential of Nature-Based Solutions (NbS) as hybrid infrastructures capable of combining risk reduction, environmental enhancement and territorial reconfiguration (European Environment Agency, 2021). The methodology integrates the analysis of post-tsunami regulatory frameworks and technical documentation with field-based observation of territorial transformations along the canal, and the interpretation of emerging spatial dynamics through the relationship between infrastructure, environmental systems and governance mechanisms. These elements provide the basis for assessing the transferability of the Japanese experience to the Italian context. The research highlights that NbS become most effective when implemented within coherent planning frameworks supported by regulatory instruments capable of aligning defence, adaptation and relocation strategies. The case study offers operational references — tools, rules and procedures — that can inform innovation in Italian local planning, enabling a shift from reactive approaches to proactive and climate-proof governance. In this perspective, risk becomes a driver of spatial, ecological and social regeneration in vulnerable coastal territories.