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Effetti indotti dalle variazioni morfologiche di una bocca lagunare sui bacini limitrofi
No full textWave forecasting dependent from bottom roughness: The case of the Marano and Grado Lagoon
Full text linkSeveral forecasting curves have been developed in order to provide a useful estimation of the wind wave field generated on shallow depths. In particular, these equations can be successfully applied in confined and sheltered basins, such as lakes, or even lagoons and semi – enclosed estuarine in coastal environments. The important role of the bottom friction dissipation in the generation process has been deeply recognized, leading to a reformulation of the available curves in terms of the equivalent bed roughness. In the present study, the recent new set of equations is considered and applied to a coastal lagoon. The results in terms of significant wave height and peak period are compared to those derived from a complete numerical model and other previous curves. The performed application corroborates and further validate the forecasting equations
A complete morphodynamic study to face a river engineering issue
Full text linkThe last reach of the Tagliamento River, in North East Italy, is progressively changing its planimetric geometry, causing sediment deposition close to a port and preventing the regular navigation in that area. In the present paper, this river engineering issue has been addressed in a complete way, first investigating the cause which brought to the present situation, and then proposing a number of design solution to mitigate the problem. Some of them have been analyzed by means of a morphodynamic numerical model, reproducing the effects on the bottom height of an average year in terms of flow and tides. The results of each simulation are compared to those of the present situation, in order to underline any advantages of the proposed design solution
Improvement in the sediment management of a lagoon harbor: The case of marano lagunare, italy
No full textPort 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
Two-inlet lagoon systems: Interaction between basins and effects on tidal prisms
No full textIn a lagoon basin, the tidal prism is related to the section of its inlet by a simple monomial relationship (LeConte 1905; O’Brien 1931; Jarrett 1976). Although it is not dimensionally correct and there are sophisticated models in two or three dimensions, this relationship is widely used because of its simplicity. Having a simple relationship can be very important, especially when it is necessary to make quick, albeit approximate, evaluations. To maintain this simplicity, the same monomial relationship is often used in multi-inlet lagoons, even if the initial assumptions are not fully met. Another difficulty in applying a monomial relationship to a multi-inlet lagoon is the definition of the area of each basin. In this paper we propose a simple Eulerian, hydrodynamic, one-dimensional approach based on the dynamic response of a non-linear harmonic system and a harmonic analysis of the interaction between two basins in a lagoon system. With such an approach, the definition of the basin surface is overcome simply by working on topographic control basins. The study leads to the definition of a relatively simple relationship for the estimation of tidal prisms, while maintaining the flexibility of a monomial relationship. If the geometrical characteristics and the bottom friction of the inlet channel, the topographic surface of the basins and the amplitude of the tide in the open sea are known, this relationship can be used to estimate the tidal prism in individual basins.The application of this relationship to two-dimensional numerical cases and real multi-inlet lagoons shows good agreement with experimental data
New Fetch- and Depth-Limited Forecasting Curves Depending on Bed Roughness
No full textPredicting wind waves within confined and shallow basins is very important, given the
decisive role they play in the resuspension mechanisms of sediments and nutrients
from the bottom, on which the main morphological and environmental changes
depend. Pascolo et al. (2019) proposed a set of wave forecasting curves for fully
developed conditions in finite depth, which consider the bottom roughness as an
additional variable, since it plays a fundamental role in the wave energy dissipation
during the generation process. The present study incorporates and integrates the
results previously obtained by Pascolo et al. (2019) and provides the growth curves in
the complete form, taking into account also the limitation on fetch. A numerical
approach on a simplified domain has been adopted and statistical analyses on the fit of
the curves to numerical results have been performed. The new set of equations
confirms the variability of the wave heights and periods as a function of the bottom
conditions which can change due to the presence of bedforms, vegetation or particle
size differences. Applications at different conditions of depth, fetch and roughness
have been analysed, in order to confirm the validity of the new growth curves
Sea defences design in the vicinity of a river mouth: The case study of Lignano Riviera and Pineta
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