Search Results (4)

Siltation around the harbour entrance poses significant challenges to the navigational safety and operational stability of coastal ports. Previous research has predominantly focused on sedimentation mechanisms in sandy coastal environments, while studies on silt-muddy coasts remain scarce. This paper investigates the causes of siltation around the entrance of Binhai Port in Jiangsu Province, China, utilising field observation data and a two-dimensional tidal current numerical model, with emphasis on hydrodynamic variations and sediment dynamics. Observations reveal that tidal currents induce sediment deposition in the outer harbour entrance area, whereas pronounced scouring occurs near breakwater heads. During extreme weather events, such as Typhoons Lekima (2019) and Muifa (2022), combined wind–wave interactions markedly intensified sediment transport and accumulation, particularly amplifying siltation at the entrance, with deposition thicknesses reaching 0.5 m and 1.0 m, respectively. The study elucidates erosion–deposition patterns under combined tidal, wave, and wind forces, identifying two critical mechanisms: (1) net sediment transport directionality driven by tidal asymmetry, and (2) a lagged dynamic sedimentary response during sediment migration. Notably, the entrance zone, functioning as a critical conduit for water– sediment exchange, exhibits the highest siltation levels, forming a key bottleneck for navigational capacity. The insights gleaned from this study are instrumental in understanding the morphodynamic processes triggered by artificial structures in silt-muddy coastal systems, thereby providing a valuable reference point for the sustainable planning and management of ports. Full article

The hydrodynamics and sediment transport at the microtidal harbour of La Spezia Arsenale (Liguria, Italy) were studied through a numerical approach, with the objective of providing useful information for: (1) the understanding of the hydro-morphodynamics of microtidal harbour settings and (2) the operation management and planning for the Arsenale, the pivotal harbour for the Italian Navy. Three different scenarios were used to parametrically gain knowledge on the role of extreme (100-year return period) meteomarine forcing. FUNWAVE and Delft3D were used to simulate, respectively, the wave propagation from the open sea toward the Arsenale and the influence of two freshwater streams on the basin circulation. The first scenario was aimed at understanding the effect of wind waves and swell on the basin dynamics; the second scenario was set up to inspect the role of the rivers’ discharges on the Arsenale hydro-morphodynamics; the third scenario combined all of the above forcings. All the simulations also included the tidal forcing and were run under two different wind directions. We found that the hydrodynamics inside the Arsenale were mainly influenced by the tide and the wind; the former caused the water to enter/exit the basin during the flood/ebb phases, respectively, and the latter influenced the circulation cell, whose sense of rotation depended on the wind direction. In addition, the discharge of the Lagora stream, debouching into the sea close to the Arsenale entrance, partially entered the basin and created an eddy whenever its direction was opposite to that of the wind-forced circulation cell, while the Caporacca stream, flowing directly into the Arsenale, mainly fed the dominant circulation without altering it. On the other hand, the morphodynamics were strongly affected by the rivers’ discharges, which were solely responsible for the supply of sediment to the basin. Also, the major influence on the sediment transport was exerted by the rivers and the wind forcing. Small sedimentation rates were observed in the Arsenale close to the rivers’ mouths, particularly after the occurrence of the rivers’ discharges, while no siltation due to waves took place. This study evaluated for the first time the influence of freshwater streams flowing nearby/into the Arsenale, representative of semi-enclosed microtidal ports located in the vicinity of rivers. It was found that the contribution of the rivers to the hydro-morphodynamics of the Arsenale cannot be neglected; indeed, it represents one of the main forcings of the harbour dynamics and should, therefore, be considered from a management viewpoint. Full article

In 1997, in front of the Pescara Harbour (Italy), a detached breakwater was constructed. In the successive years, the sediment transport due to the combined action of waves and coastal currents, in the area between the detached breakwater and the entrance of the Pescara Harbour, produced an accumulation of about $\mathrm{40,000}{ \mathrm{m}}^3$ of sediment per year. In this paper, the causes of the accretion of the bottom elevation in front of the Pescara Harbour entrance and the effects produced by the existing detached breakwater are investigated. The effects on the sediment transport of the introduction of a new submerged breakwater designed to protect the entrance of the harbour from sediment siltation are investigated. In particular, the ability of the designed submerged breakwater, located orthogonally to the longshore current, to intercept the aforementioned solid material and to significantly reduce the accretion of the bottom in the area in front of the harbour entrance, was numerically verified. Numerical simulations were carried out by means of a model of the bottom-change composed of two sub-models: a two-dimensional phase resolving model that is used to calculate the fluid dynamic variables changing inside the wave period and a second sediment transport sub-model to simulate the bottom changes, in which the suspended sediment concentration is calculated by the wave-averaged advection–diffusion equation. The equations of motion, in which the vector and tensor quantities are expressed in Cartesian components, are written in a generalised curvilinear coordinate system. The fully nonlinear Boussinesq equations are written in an integral form and used to simulate the velocity fields. Full article

In this paper we propose a three-dimensional numerical study of the coastal currents produced by the wave motion in the area opposite the Cetraro harbour (Italy), during the most significant wave event for the coastal sediment transport. The aim of the present study is the characterization of the current patterns responsible for the siltation that affects the harbour entrance area and the assessment of a project solution designed to limit this phenomenon. The numerical simulations are carried out by a three-dimensional non-hydrostatic model that is based on the Navier–Stokes equations expressed in integral and contravariant form on a time-dependent curvilinear coordinate system, in which the vertical coordinate moves in order to follow the free surface variations. The numerical simulations are carried out in two different geometric configurations: a present configuration, that reproduces the geometry of the coastal defence structures currently present in the harbour area and a project configuration, which reproduces the presence of a breakwater designed to modify the coastal currents in the area opposite the harbour entrance. Full article