Reviving the Heritage Water Network
A sustainable, adaptive blue-green network for Saga, Japan
Kanako Inai (TU Delft - Architecture and the Built Environment)
I. Bobbink – Mentor (TU Delft - Landscape Architecture)
M.T.A. van Thoor – Mentor (TU Delft - Heritage & Architecture)
M.G. Elsinga – Graduation committee member (TU Delft - Urban Development Management)
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Abstract
Situated on the Tsukushi Plain in Japan, Saga City developed a distinctive water network in response to the extensive tidal range of the Ariake Sea and the limited irrigation water available from the surrounding mountains. This system enabled the city to cope with drought and flooding, becoming the cultural and spatial backbone of urban life.
With twentieth-century modernization, centralized water infrastructure, and depopulation, however, the canal network lost everyday relevance: many canals were filled, consolidated, or culverted, and remaining reaches suffer from sedimentation and overgrowth. Saga’s identity as a “water city” has weakened, and vulnerability to extreme rainfall, pluvial flooding, and biodiversity loss has increased.
Adopting the framework of Landscape Biographies (Kolen & Renes, 2015), which views landscapes as continuously rewritten by human–nature interactions, this thesis reconsiders Saga’s canal system as a local asset for sustainable development under demographic and climatic stress. The central question is how the forgotten water network can be reactivated as blue-green structures that strengthen climate resilience, ecological health, and community life while retaining cultural value.
The research operates from regional to community scales using a mixed methodology: archival and map analysis to trace formation and urban structuring roles; field surveys and mapping to document present conditions and adjacent land uses; and spatial analysis to identify opportunities to reconnect water with urban voids (vacant or underused sites) and community spaces. Design exploration translates these insights into testable spatial strategies.
The proposal reorganizes the water system as a low-maintenance, climate-responsive blue-green framework that respects historic structure while shifting from human-centered to nature-centered logics. In parallel, it integrates urban voids with canals to weave a fragmented city into a continuous public-space network, making hidden water visible and usable. Design principles extracted from historical water practices are implemented in these places.
Reactivating the network is expected to deliver tangible benefits (improved water management, flood mitigation, ecological connectivity, and restoration) and intangible values (civic pride, place identity, renewed appreciation of heritage). Saga’s case advances an adaptive transformation beyond preservation by extracting the essence of local assets and reorganizing them in response to changing times, offering a transferable model for other regional cities.