肝属川水系における多自然川づくり事後評価の取組みと今後の川づくりへの展開について

抄録

Post-evaluation was carried out for 71 sites of nature-oriented river work projects on Kimotsuki River system in Kagoshima Prefecture. The sites were categorized into three groups according to its project aim; (1) improvement of river landscape, (2) conservation and generation of habitats and breeding sites for flora and fauna and (3) improvement of access to waterfront. For each group, several indicators were chosen for evaluation and we scored them into three grades by field survey. As a result of the evaluation, positive impacts of the projects, such as sufficient vegetation rehabilitation that matches the surrounding landscape and provision of gaps by riprap, stonework revetment and waterside vegetation for hiding and habitation for aquatic organisms, were observed. However, waterline lacking in diversity, steepening riverbank and poor maintenance of water recreational facilities were identified as issues. It was considered that it is desirable to design river works which allow natural geomorphological processes to take place as it leads to complex waterline and slope changes.