Hydrodynamics of the Po River‐Delta‐Sea System

Abstract

In this study we investigated the hydrodynamics and the interaction between riverine and marine waters in the Po River-Delta-Sea (RDS) system (Italy). Through the application of an unstructured 3D numerical model to a domain comprising the Po river branches, seven coastal lagoons and the shelf sea, many of the hydrodispersive phenomena evolving from the interaction of the different water bodies of the RDS system were described. The model was successfully calibrated and validated for water levels, fluxes at the inlets and at the river branches, and water temperature and salinity observations. The use of such a comprehensive approach allows the characterization of the general hydrodynamics of all the components of the Po RDS system, of the water exchange between different water bodies as well as the Po river discharge distribution among all branches. The analysis of calculated coastal current patterns in the prodelta of two different years and during a flood event confirms that the Po River is the main driver of the baroclinic coastal sea circulation. However, when strong winds occur (Sirocco and Bora), the surficial circulation of the shelf area is significantly modified. Generally, the lagoons of the Po RDS system can be considered hydrodynamically active since their tidal prisms represent a relevant fraction of each lagoon's volume. The natural consequence is that the lagoons show an active flushing with water renewal times in the order of few days. The hydrodynamics is mainly forced by the tide and is locally enhanced by riverine inputs and wind. Where freshwater inputs are significant, they are responsible of the lagoons salinity patterns that show high spatial gradients (not all the lagoons are well mixed) and temporal variability. The variability of the freshwater discharges and the complex morphology of the Po RDS allows the presence of both marine and riverine environments. describe the transport of nutrient from the catchment basin to the sea (Rasmussen et al., 2002), then Cerralbo et al. (2014) investigated the tidal transformation in Alfacs Bay (southern Ebro Delta). In Greece, MAICU ET AL.Key Points: • The application of a 3-D shallow water equation hydrodynamic model simulated the circulation, freshwater mixing, and residence time in the Po River-Delta-Sea system • The hydrodynamic characterization of the different water bodies, their mutual interaction, and mixing properties were studied • The spatial and temporal variability of the renewal times and flushing properties of the lagoons were investigated, as like the main natural factors driving them

Tidal modulation of river-flood deposits: How low can you go?

“…3). The flow simulated at the Pila mouth is always unidirectionally seaward during the river flood, in agreement with Maicu et al (2018). Because the steepness of the water profile is directly proportional to the flow velocity (Lamb et al, 2012), low tides force higher flow velocity.…”

“…Spring and neap tides in the northern Adriatic Sea have amplitudes of ∼86 cm and 20 cm, respectively. At the Pila channel, the flux is reversed during flood tide, when river discharge is <1000 m 3 /s (Maicu et al, 2018). Seasonal Po River floods typically reach the sea during fair-weather conditions (Wheatcroft et al, 2006).…”

Sediment Transport Mechanisms in a Lagoon with High River Discharge and Sediment Loading

“…The Curonian Lagoon (Figure 1) is a shallow water body placed in the southeastern coasts of the Baltic Sea, separated from the sea by the Curonian Spit and connected to the open sea through only one narrow inlet in the north (Klaipėda Strait). The Klaipėda Strait is a harbor area where the depths vary from 8 to 14.5 m. The total lagoon surface area is about 1584 km 2 (with 413 km 2 in Lithuania), the volume 6.3 km 3 , the maximum length 93 km, the maximum width 46 km (in the southern part), and the mean water depth 3.8 m [27].…”

“…In this study, the three-dimensional (3D) hydrodynamic model, a transport and diffusion model, a wind wave model, and a sediment transport model (including a bed model) were used. SHYFEM has been successfully applied to many coastal environments such as river deltas, lagoons, and seas [3,22,42]. The standard model equations for hydrodynamic and sediment transport used herein have been previously published in [43] and [44], respectively.…”

“…Lagoons are the most productive water bodies in coastal environments, but are vulnerable to human activity, sensitive to climate change [2], and must be monitored and managed for saving the good environmental status. The processes in such complex systems at the land-sea transitional zone are extremely dynamic and require a holistic approach in which the river-lagoon-sea continuum should be considered [3]. Sediments have a crucial role in shaping the landscape in areas where the river enters the sea.…”