嵐山地区左岸溢水対策における景観価値の保全: 可動式止水壁の実現に至る創造的協議の過程

Abstract

2022年3月，史蹟及び名勝等の指定に基づき景観保護が求められる桂川嵐山地区において，溢水対策として全国初となる可動式止水壁が完成した．本研究では，桂川嵐山地区河川整備検討委員会資料から検討過程を分析し，住民と行政の合意形成における論点の推移と対策案の創出の要因を明らかにする．景観価値の保全において重視された8つの評価軸を設定し，検討の各段階における景観価値の具体的内容を明らかにした．住民との協議では，フォトモンタージュを用いた眺望景観の検証や現場での模型・試験施工による検証を重ねて，守るべき景観価値が共有され，新たな技術を導入した対策案が生まれた．その過程に，地元住民らとの綿密な論点・対策案の共有，景観価値に基づいた治水対策の協議と発案，行政の柔軟な対応と合意形成への配慮，があった．

In March 2022, Japan's first movable flood barrier was completed to address overflow issues in the Katsura River Arashiyama area, a designated national historic and beauty site. This study aims to elucidate the process undertaken by the Katsura River Arashiyama Area River Improvement Study Committee, the evolution of issues in consensus-building between residents and the administration, and the formulation of countermeasure proposals, through an analysis of the committee's materials. The following results were obtained: (1) Eight evaluation criteria crucial for preserving landscape values were identified, and the specific content of these values at each study stage was clarified. (2) To foster consensus with residents, landscape values to be preserved and study details were communicated through various visual representations, including photomontages and on-site model verification. (3) The process entailed sharing detailed discussion points and countermeasure proposals with local residents, proposing flood control measures aligned with landscape values, and flexibly responding to and considering consensus-building efforts by the administration.