Abstract
The prism of the Lignano tidal inlet was approximately constant over the last forty years, although the section width has halved. This has led to questions concerning the factors that most influence the tidal prism, and on the applicability of the well-known A–P relationship. A conceptual scheme of the sea–channel–lagoon system has been used to perform a sensitivity analysis of different parameters that characterize both the basin and the inlet cross-section. A 2D hydrodynamic model has been applied to evaluate the prism and compare it to the one derived by a static method, which is the basis of the analytical derivation of the A–P linkage. Three regimes have been found in the prism variability as a function of the basin extension: a linear static regime between prism and basin area; an asymptotic regime in which the prism depends only on the basin bottom friction; and an intermediate one. In addition, the roles of the inlet and channel sizes on the prism value have been investigated. The results, compared to the empirical relationships between the prism and the inlet cross-section, show that a variation in the cross-sectional area does not always corresponds to a change in tidal prism.
Highlights
The focus of the paper was to analyze the relationships between the tidal prism and the geometric and hydrodynamic factors that characterize both the inlet and the lagoon basin
The factors considered in the analysis were the following: lagoon basin extension; size of the tidal inlet; depth and length of the tidal channel; and the bottom roughness inside both the channel and the lagoon basin
A 2D hydrodynamic model has been applied to evaluate the tidal prism, which has been compared to that derived by a static model
Summary
Tidal inlets are fundamental in the morphodynamic processes of the nearby coast and of the lagoon itself They act as both sources and sinks of the sediments which are suspended from the bottom by the wave motion, which is locally generated inside the basin or outside in the open sea [2,3,4,5,6,7,8,9,10]. The competing effects of waves and tides that attempt to close and widen the inlet, respectively [11,12], shape the morphology of the channel entering the lagoon In this sense, the net exchange of sediments between the tidal basin and the sea largely affects the cross-sectional form of the tidal inlet, which adapts to dominant hydrodynamic and sediment transport conditions in the medium–long term (i.e., on the timescale of years or decades) [13]
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