Author(s): Tatsuro Sato; Tomonori Sakata; Hiroshi Takata; Yukihiro Shimatani
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Keywords: No Keywords
Abstract: In high-gradient channels, to prevent serious erosion problems, channel works on riverbed and banks have been carried out, which have induced artificially uniform and degraded river environments. Although the nature-friendly river works in mountain streams have been strongly needed, the knowledges and methodologies harmonizing disaster prevention and environmental conservation have been still limited in mountainous streams. In the Jindaigawa River, Takachiho town, Miyazaki prefecture, a river restoration project has launched in order to recreate mountainous river landscape and environments. Through the participation of the river restoration projects, I investigated the key points of environmental restoration in mountainous streams, using a landscape model and hydraulic model experiments. Firstly, landscape of the restoration channel was re-designed using landscape model, which strengthened river meandering to recover the original river line. Next, the channel designed from the view point of landscape was evaluated from the hydraulic model experience, whether the channel is safe to the planed flood (55m3/s). Hydraulic model experience is more effective than computer simulation in determining the optimal river channel because the boundary condition can be changed easily. As a result, river widening is quite effective for river environmental restoration and flood control not only in lowland rivers, but also in mountain streams. However, in high-gradient channels, river widening is not able to cope with the local fast flow. Therefore, it is important to disperse the flow energy by using the structures such as step-pool and spurdykes. .
Year: 2018