Solid transport in flooding rivers with deposition on the floodplains : experimental and numerical investigations
(2010)
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- Abstract
- (en) Rivers present a threat on the neighbourhood, the houses and infrastructures when, following a major flood, they overflow their main channel and invade the floodplains. Consequent damage is often aggravated by muddy deposits, especially in urban areas. In this context of growing flood risk, due to climate changes, studies centred on compound channel flows and sedimentation processes have undergone increasing interest. Flow in compound channels is complex and present three-dimensional features which affect the transfer of suspended matter from the fast flowing main channel to the slower floodplain flow, separated by a strong shear layer. This dissertation aims at a better understanding of convection and diffusion phenomena and fine sediment deposit formation on floodplains during overbank flow. Transfer processes between the channel subsections due to turbulent exchanges are studied experimentally and numerically. Experimental mixing reference data was provided through solute injections in a laboratory flume and tracing of the plume. Lateral sediment transfer and subsequent deposition patterns are also investigated. Novel experiments were designed in a flume equipped with sediment-laden water recirculation and upstream sediment injection systems. Weighting of deposited sediment and digital imaging are used to evaluate the deposition formation. Numerical simulations show how the critical mobility parameter and the bed shear control the erosion fluxes. The spatial distribution lacks of realism due to the impossibility of the model to represent mobile deposition. However, modelled sediment deposition on the floodplains concurs with collected sediment mass during experiments, if the model parameters are correctly adapted to the floodplain surface conditions (micro-topography).
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Fraselle, Q. (2010). Solid transport in flooding rivers with deposition on the floodplains : experimental and numerical investigations. https://hdl.handle.net/2078.5/148306