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Effects of Boulder Arrangement on a Gravel-Bed Flow

Author(s): Chamika De Costa; N. Henrys; S. Coleman

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Abstract: The purpose of this project is to investigate the flow characteristics, including velocity and turbulence distributions, in a river or culvert in relation to changes in arrangements and size of boulder roughness elements. The application of this is then to create flow ideal for managing sediment transport and erosion of banks, and also for creating favorable habitats for plants and fish. The research was conducted in a laboratry by placing boulders in specific arrangements in a shallow flume. Two arrangements were tested in different roughness spacings. 1) a diamond arrangement, and 2) a rectangular arrangement. Measured velocities were faster for the diamond arrangement than the rectangular arrangement, upstream and downstream of the boulder. The diamond arrangement gave lower turbulence intensities. Increasing the distance between boulders resulted in increased velocities and decreased turbulence intensities. In addition to this the velocity vectors in the diamond arrangement consistently aimed in a uniform direction in the direction of flow. While the turbulent nature of the flow in the rectangular arrangement also showed. This in some occasion was by velocity vector in the reverse direction of the average flow of water. In conclusion the diamond arrangement gave substantially better results for velocity and turbulence distribution.


Year: 2010

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