Morphodynamic Model Suitable for River Flow and Wave-Current Interaction

2018

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Abstract:The silting of tidal channels is a natural process that affects several shallow lagoons and makes it difficult to navigate, requiring regular maintenance interventions. This phenomenon is the result of the complex non-linear interaction between tidal currents and wave motion. In this work, the morphodynamic evolution of the Marano and Grado lagoon is investigated by means of a two-dimensional horizontal (2DH) morphological-hydrodynamic and a spectral coupled model. An innovative procedure to reproduce the overall bathymetric changes in the medium term and, in particular, the volumes deposited inside channels, is presented. An average year with a sequence of winds and tides acting over that time was reconstructed, carrying out cross correlation techniques and spectral analyses of measured data. The predicted morphological evolution matches the annual dredged volumes in the lagoon critical branches and shows the distribution of erosion and deposition of cohesive sediments according to spatially variable values of critical shear stress.

Section: ∂N ∂Tmentioning

confidence: 99%

Lagoon Sediment Dynamics: A Coupled Model to Study a Medium-Term Silting of Tidal Channels

2018

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“…The former is a bidimensional (2DH) finite volume shallow water in-house model, based on hydrodynamic equations, advection-diffusion equations of granular and cohesive suspended sediment concentration and a continuity equation of sediments at the bottom, as described in [38,49]. These equations allow the temporal bed evolution to be estimated by also taking into account the forcings due to the radiation stress tensor and the contribution of the wave motion to the bottom shear stresses τ b , which is evaluated according to Soulsby [50] as a nonlinear combination of the amount due to the current and the wave motion.…”

Section: Numerical Modelmentioning

confidence: 99%

Improvement in the Sediment Management of a Lagoon Harbor: The Case of Marano Lagunare, Italy

2021

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Port silting is a common and natural process which often causes serious inconveniences for safe navigation and requires expensive dredging operations to keep the port operative. Sediment deposition is closely related to the exchange water between the basin and the surrounding environment; one way to limit deposits is by reducing the flow entering the port. However, this may be in contrast with the need for adequate sediment quality, which in turn is closely related to an appropriate water current. This seems to be particularly important in lagoon environments, where sediments are often polluted, making its disposal more complicated and costly. The present paper investigates the situation of the port of Marano Lagunare (Italy) by means of a bidimensional morphological-hydrodynamic and spectral coupled model. To reduce the sediment input into the port, the closure of a secondary port entrance is usually suggested. However, this work demonstrates that a complete dredging of the secondary port inlet allows for an increase in water circulation or efficiency renewal, which ensures a better oxygenation at the bottom of the canals.

“…(τ mx , τ my ) are the components along x and y, respectively, of the mean bottom shear stress τ m , due to the interaction of current and wave motion. Among all the theories available in literature which combine their effect, in the present paper the formula proposed by Soulsby [31] has been preferred [33]:…”

Section: Numerical Schemementioning

confidence: 99%

Wave–Current Interaction: A 2DH Model for Turbulent Jet and Bottom-Friction Dissipation

2018

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A correct representation of the non-linear interactions between waves and currents is one of the key points when studying the morphological evolution of nearshore environments, in particular close to river mouths or tidal inlets. Undoubtedly, the numerical modelling of similar phenomena can be very complex and computationally demanding, given the size of the domains. In the present paper, a two-dimensional horizontal (2DH) numerical model is applied to investigate the hydrodynamics of a turbulent jet current interacting with frontal waves, preparatory to the study of morphodynamical processes. The purpose is to reproduce accurately the turbulence of the current flow, which develops in both vertical and horizontal planes, even with the simplifications of depth-averaged velocities. Moreover, the bottom shear stress induces a mechanism of dissipation, which acts both on the jet hydrodynamics and on the wave field. Significant attention is given to this process, which turns out to be crucial in shallow waters. The present model, based on classic shallow-water equations and wave action balance, is applied to a literature test. Comparisons with theoretical and numerical outcomes are shown, the latter obtained with a quasi-3D model.