History of river restoration
Much like in Europe, Japanese rivers have been used for domestic purposes, agriculture and navigation, among others, until 1964, when they were placed under heavy restrictions. With the intensification of flood hazards, rivers in a city like Tokyo had conventional engineering measures such as levees, dykes and embankments installed on them. However, under decision-makers' direction, including mayors, river restoration has been adopted as a profound policy to make rivers more accessible to people since 2013. Conversely, advocacy for river restoration in Germany has been led by civil society and dates as far back as the late 1800s. The award-winning Isar experience, for instance, took decades of planning and stakeholder consultation from the mid-1900s until the shovel hit the ground in 2000. Yuta's research heels such river restoration efforts and aims to compare and learn across regions.
Objectives in Munich and Okazaki
The Isar Restoration was motivated predominantly by a) flood hazard mitigation through the reclamation of floodplains, improvement in river retention and widening of the riverbed; b) ecological restoration by way of fostering flora and fauna habitats, improvement in the longitudinal and lateral continuity of the river and a general improvement in ecological processes and c) improvement in the recreational possibilities in and around the river through making the waterline more accessible and developing an attractive landscape for water based recreation. However, using experiences from the city of Okazaki, Yuta showed that recreation and aesthetic value are more important for citizens than hazard mitigation and fostering biodiversity. As he further showed, all relevant clusters of people—old or young, working with nature or not, born in Okazaki or not, etc.—perceive rivers as open spaces, away from the usual busy cityscape with high-rise buildings, for recreation. Additionally, biodiversity concerns are underrepresented in the river management framework.
From discussions, similarities could be identified between the use of restored rivers in Japan and Germany regarding energy production and littering in river sites.
A couple of factors were considered essential building blocks for up-scaling river restoration, as nature-based solutions, in Japan. First, river governance is significantly flexible compared to Germany. This can hasten the implementation time of measures. Also, citizens are highly interested in visiting rivers for recreation, even if it means travelling long distances to access them. These factors could promote river restorations as nature-based solutions which are high on global climate and resilience building policy because of their multifunctionality, cost-effectiveness, long-term efficiency and general sustainability.