IAHR, founded in 1935, is a worldwide independent member-based organisation of engineers and water specialists working in fields related to the hydro-environmental sciences and their practical application. Activities range from river and maritime hydraulics to water resources development and eco-hydraulics, through to ice engineering, hydroinformatics, and hydraulic machinery.
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You are here : eLibrary : IAHR World Congress Proceedings : 32nd Congress - Venice (2007) : THEME A: Engineering and Management of Fresh-water Systems : Effect of the vertical structure of a porous bed on hyporheic exchange
Effect of the vertical structure of a porous bed on hyporheic exchange
Author : Mattia Zaramella, Andrea Bottacin, Andrea Marion, Aaron I. Packman
Mass fluxes through the interface between a surface flow and the porous subsurface are driven by hydrodynamic forcing. Transport through a thin surface layer of the bed is dominated by turbulent mass exchange. The depth of this layer scales with the sediment diameter. The deeper zone of the bed underlying this surface layer is affected by the advective exchange induced by dynamic pressure head gradients over the bed surface. The bed structure is the result of sediment transport processes occurring at different timescales. Some structures develop as vertical non-homogeneities produced by grain sorting processes such as armouring and size-selective erosion and sedimentation. In order to analyse hyporheic processes linked to these vertical structures a stratified bed structure has been artificially created in a laboratory flume. An armoured bed has been created starting from a sediment bed with non-uniform grain size and letting the armoured layer develop naturally. The grain size distribution was measured using surface sampling techniques. Both natural armouring and stratification enhance mass exchange, enhancing the vertical transport component. For higher timescales vertical structure limit the interface exchange hindering penetration towards the deeper layers.
File Size : 1,507,548 bytes
File Type : Adobe Acrobat Document
Chapter : IAHR World Congress Proceedings
Category : 32nd Congress - Venice (2007)
Article : THEME A: Engineering and Management of Fresh-water Systems
Date Published : 01/07/2007
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