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Improvement of Diversion Weir and Surrounding Vegetation Condition Effects on Diversion Discharge in the Asahi River

Author(s): Keisuke Yoshida; Shiro Maeno; Ryosuke Akoh; Kaho Yamaguchi; Tomohiro Iwaki; Syunsuke Fujita; Yasutaka Hirai

Linked Author(s): Keisuke Yoshida

Keywords: River improvement works; Diversion discharge; Trimming vegetation

Abstract: This paper describes numerical investigations of the effects of vegetation establishment at sand bars in rivers on a diverting discharge at a fixed weir installed between the lower Asahi River and a distributary, the Hyakken River, in Japan. For this study, we developed a horizontal two-dimensional flow model and validated it using observation data obtained during two floods occurring in 2011 and2013. Then, we conducted numerical simulations using the model, considering some scenarios of vegetation conditions. Based on the simulation results, we examined the hydraulic characteristics of the diverting flows and the related diverting discharge values depending on vegetation conditions. Results showed that the model outputs are well consistent with the observation data for these flood events. Additionally, results clearly presented that established vegetation in rivers serves an important role in reducing the flow capacity and the related water elevations. Results show that the location of vegetation establishment in rivers determines the value of the diverting discharge. Therefore, we must regularly monitor both the dynamics of sand bars and the vegetation habitat over a wide area in these rivers. We must also consider the secular change of the relation for flood control tasks.


Year: 2016

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