Abstract

LARSON, Magnus  and  HANSONA, Hans. Model of the evolution of mounds placed in the nearshore. RGCI [online]. 2015, vol.15, n.1, pp.21-33. ISSN 1646-8872.  https://doi.org/10.5894/rgci530.

A one-dimensional mathematical model is presented that describes the cross-shore evolution of a long linear mound of non-cohesive sediment placed in the nearshore and exposed to non-breaking waves. The equation for the transport rate accounts for wave asymmetry and gravity, and the net rate is expressed by reference to an equilibrium profile shape. Simplifications reduce the governing equation for mound evolution to the diffusion equation, for which analytical solutions are available for various initial shapes of the mound. Temporal and spatial dependencies governing mound evolution are obtained from the analytic solutions; for example, a doubling of the wave height implies a certain mound response in 1/8 of the time compared to the original conditions. The governing equation is also solved numerically in order to avoid schematization of the forcing, initial, and boundary conditions. Both the analytical and numerical models are compared with data on mound evolution from several sites around the world. Model predictions agree with trends in measurements of four mounds at widely different sites. An example is given concerning the application of the analytical model for preliminary mound design. The formulation presented also applies to infilling of dredged trenches with lengths much greater than their widths.

Keywords : sediment transport; dredging; profile evolution; beach nourishment; mound design.

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