Author(s): Junya Yamamoto; Yasunori Muto; Yasuo Anase; Takao Tamura
Linked Author(s): Yasunori Muto
Keywords: Green infrastructure; Vegetation management; Bank erosion; Flow condition analysis
Abstract: Flood flow due to typhoons 1411 Halong and 1412 Nakri induced severe bank erosion of 50 m long at Nishihara point in the Yoshino River, the left bank of about 37 km from the river mouth. Not only the bed topography but also vegetation is believed to distort flow structure, enhancing the flow toward the bank with a large angle. In order to avoid such a situation, vegetation management is quite important. At the same time, vegetation can also be used as a green infrastructure against floods, such as bank protection and flow baffler, if it is properly arranged. Thus establishing methodology on vegetation management in river channels is strongly needed. In this research, in order to find out the vegetation arrangement to suppress river erosion, we examine the placement where the flow against the bank is relaxed by changing the local vegetation arrangement. As a research method, flow dynamics analysis is performed by adding vegetation model to depth averaged flow model in the generalized curvilinear coordinate system. The characteristics of vegetation in Nishihara point include bamboo forest on the right bank and Salix forest on the left bank. As the evaluation index, for bank erosion we used the non-dimensional shear stress and the angle between flow direction and the dike alignment. From the results, cutting down the bamboo forest on the left bank makes the non-dimensional shear stress and the angle between flow direction and the dike alignment big. Also, the vegetation arrangement which affect little was present vegetation arrangement.
Year: 2018