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A MATLAB routine, based on a Double Multiple Stream Tube model, developed to quickly predict the performance of cross-flow hydrokinetic turbine, here is presented. The routine evaluate flow data obtained with the open-source marine circulation code SHYFEM. The tool can establish the best locations to place tidal devices taking into account bathymetric constraints and the hydrokinetic potential. Hence, it can be used to decide the best set of geometrical parameters. The geometrical variables of our analysis are turbine frontal area, aspect ratio and solidity. Several sub-models, validated with 3D and 2D CFD simulations, reproduce phenomena such as dynamic stall, fluid dynamic tips losses and the lateral deviation of streamlines approaching the turbine. As a case study, the tool is applied to an area of the northern Adriatic Sea. After having identified some suitable sites to exploit the energy resource, we have compared behaviours of different turbines. The set of geometrical parameters that gives the best performance in terms of power coefficient can vary considering several locations. Conversely, the power production is always greater for turbine with low aspect ratio (for a fixed solidity and area). Indeed, shorter devices benefit from higher hydrokinetic potentials at the top of the water column.

Our aim was to embed a 2D analytical model of a cross-flow tidal turbine inside the open-source SHYFEM marine circulation code. Other studies on the environmental impact of Tidal Energy Converters use marine circulation codes with simplified approaches: performance coefficients are fixed a priori regardless of the operating conditions and turbine geometrical parameters, and usually, the computational grid is so coarse that the device occupies one or few cells. In this work, a hybrid analytical computational fluid dynamic model based on Blade Element Momentum theory is implemented: since the turbine blades are not present in the grid, the flow is slowed down by means of bottom frictions applied to the seabed corresponding to forces equal and opposite to those that the blades would experience during their rotation. This simplified approach allowed reproducing the turbine behavior for both mechanical power generation and the turbine effect on the surrounding flow field. Moreover, the model was able to predict the interaction between the turbines belonging to a small cluster with hugely shorter calculation time compared to pure Computational Fluid Dynamics.

Climate scenarios produce climate change-related information and data at a geographical scale generally not useful for coastal planners to study impacts locally. To provide a suitable characterization of climate-related hazards in the North Adriatic Sea coast, a model chain, with progressively higher resolution was developed and implemented. It includes Global and Regional Circulation Models representing atmospheric and oceanic dynamics for the global and sub-continental domains, and hydrodynamic/wave models useful to analyze physical impacts of sea-level rise and coastal erosion at a sub-national/local scale. The model chain, integrating multiple types of numerical models running at different spatial scales, provides information about spatial and temporal patterns of relevant hazard metrics (e.g., sea temperature, atmospheric pressure, wave height), usable to represent climate-induced events causing potential environmental or socio-economic damages. Furthermore, it allows the discussion of some methodological problems concerning the application of climate scenarios and their dynamical downscaling to the assessment of the impacts in coastal zones. Based on a balanced across all energy sources emission scenario, the multi-model chain applied in the North Adriatic Sea allowed to assess the change in frequency of exceedance of wave height and bottom stress critical thresholds for sediment motion in the future scenario (2070&ndash, 2100) compared to the reference period 1960 to 1990. As discussed in the paper, such projections can be used to develop coastal erosion hazard scenarios, which can then be applied to risk assessment studies, providing valuable information to mainstream climate change adaptation in coastal zone management.

Satellite imagery provides evidence of complex mixing dynamics in the coastal zone in front of multiple mouth deltas. One peculiar feature, identified in front of the Po Delta (Italy), consists in warmer water bulges present in some periods in the coastal zone between the river mouths. Such features are evident during both high and low river discharge. Through an integrated approach based on the analysis of satellite imagery, in situ field data and a high-resolution oceanographic model, representing the whole river-delta-sea system, we investigated the relative contribution of the different forcing in controlling coastal mixing of riverine waters. The results evidence that the occurrence of these warmer saltier water bulges is due to upwelling induced by the combined action of tides and wind regimes aligned along coastline. Winds from the land and along the coast drive the upwelling through the well-known mechanism described by Ekman. The presence of river discharge enhance the water column stratification, creating the conditions in which tidal action follows the tidal straining theory. Both processes are identified in modelling results. The occurrence of these localized coastal waters with peculiar thermohaline characteristics, detectable on satellite imagery of the area, can be relevant in the definition of the freshwater areas of influence and the mechanisms of riverine water mixing in the near coastal zone. This can shed some light, eventually, on characterizing the sediment dynamics, as well as the thermohaline properties of waters in the area, and also to identify eventual impacts on the local ecosystems and fishery.

Dense water (DW) formation commonly occurs in the shallow Northern Adriatic Sea during winter outbreaks, when there is a combination of the cooling of surface waters by the winds and high salinity as a result of reduced river inputs. These DWs subsequently propagate southwards over a period of weeks/months, eventually arriving in the Southern Adriatic Sea. The investigation is based on a new nonhydrostatic (NH) formulation of the 3D finite element model SHYFEM that is validated for a number of theoretical test cases. Subsequently this model is used to simulate, through high-resolution numerical simulations, an extreme DW event that occurred in the Adriatic Sea in 2012. We perform both hydrostatic (HY) and NH simulations in order to explicitly see the impact of NH processes on the DW dynamics. The modeled results are compared to observations collected in the field campaign of March–April 2012 in the Southern Adriatic Sea. The NH run correctly reproduces the across isobath bottom-trapped gravity current characterizing the canyon DW pathways. It also more accurately captures the frequency and intensity of dense water cascading pulsing events, as the inclusion of NH processes produces stronger currents with different DW mixing characteristics. Finally, the NH run simulates internal gravity waves (IGW), generated during the cascading at the edge of the canyon, which propagate downslope. This IGW activity is not captured in the HY case.

The morphology of scour holes at tidal channel confluences was investigated through high-resolution acoustic mapping of the channel network in the Venice Lagoon (Italy). Our investigation identified 29 confluence scours ranging in depth from 7 to 26m and characterized by different confluence geometry and scour properties. Scours were found at the confluence of two or more channels, having equal or unequal bed heights and a diverse confluence planform geometry. The main morphological characteristics of the scours were compared to literature data from fluvial environments. Like in rivers, the scour depth tends to increase with the angle of the confluence. Moreover, the maximum depth of the confluence scours in the Venice Lagoon is positively correlated with the tidal prism of the channels joining the confluence. The investigation of the seafloor features in the scour holes highlighted that, generally, small- and medium-scale bedforms are present on the gentle slope. The scours' seafloor roughness indicated that in tidal channels both ebb and flood flows combine in shaping the confluence morphology. In addition, the analysis of historical bathymetric datasets dating back to the 1800s allowed us to analyze the morphological evolution of two of these erosive features. Our findings revealed the century-scale morphological dynamics of scour holes, as a consequence of changes in the flow regime.

As the size of vessels progressively increases to compete in the global trade, the impact evaluation of navigation in waterways and shallow coastal ecosystems become more important. Therefore, suitable tools to investigate processes are required to support a sustainable management of ship traffic. This work tests a new methodology, based on a numerical model chain, that reproduces the hydrodynamic field close to the ship hull and the ship-induced wave propagation in the surrounding shallow areas. The model chain includes an unstructured hydrodynamic model forced by the near-field estimation of a computational fluid dynamics simulation. The modeling system has been applied to a major navigation channel and surrounding tidal flats in the Venice Lagoon (Italy). Field observations and a theoretical framework were used to characterize the ship waves and to validate the modeling system. Results show that the deeper the initial depression, the larger the dissipation over the tidal flat. In these conditions smaller vessels sailing at higher speed produce smaller waves with low amplitudes compared to larger ships traveling at lower speed. We considered vessels moving at different speeds providing useful information to evaluate impacts and to define criteria for decision support systems for a sustainable management of navigation.

Thirty-meters resolution turbidity maps derived from Landsat 8 (L8) images were used to investigate spatial and temporal variations of suspended matter patterns and distribution in the area of Po River prodelta (Italy) in the period from April 2013 to October 2015. The main focus of the work was the study of small and sub-mesoscale structures, linking them to the main forcings that control the fate of suspended sediments in the northern Adriatic Sea. A number of hydrologic and meteorological events of different extent and duration was captured by L8 data, quantifying how river discharge and meteo-marine conditions modulate the distribution of turbidity on- and off-shore. At sub-mesoscale, peculiar patterns and smaller structures, as multiple plumes and sand bars, were identified thanks to the unprecedented spatial and radiometric resolution of L8 sensor. The use of these satellite-derived products provides interesting information, particularly on turbidity distribution among the different delta distributaries in specific fluvial regimes that fills the knowledge gap of traditional studies based only on in situ data. A novel approach using satellite data within model implementation is then suggested.

In this work we consider a numerical study of hydrodynamics in the coastal zone using two different models, SHYFEM (shallow water hydrodynamic finite element model) and MITgcm (Massachusetts Institute of Technology general circulation model), to assess their capability to capture the main processes. We focus on the north Adriatic Sea during a strong dense water event that occurred at the beginning of 2012. This serves as an interesting test case to examine both the models strengths and weaknesses, while giving an opportunity to understand how these events affect coastal processes, like upwelling and downwelling, and how they interact with estuarine dynamics. Using the models we examine the impact of setup, surface and lateral boundary treatment, resolution and mixing schemes, as well as assessing the importance of nonhydrostatic dynamics in coastal processes. Both models are able to capture the dense water event, though each displays biases in different regions. The models show large differences in the reproduction of surface patterns, identifying the choice of suitable bulk formulas as a central point for the correct simulation of the thermohaline structure of the coastal zone. Moreover, the different approaches in treating lateral freshwater sources affect the vertical coastal stratification. The results indicate the importance of having high horizontal resolution in the coastal zone, specifically in close proximity to river inputs, in order to reproduce the effect of the complex coastal morphology on the hydrodynamics. A lower resolution offshore is acceptable for the reproduction of the dense water event, even if specific vortical structures are missed. Finally, it is found that nonhydrostatic processes are of little importance for the reproduction of dense water formation in the shelf of the north Adriatic Sea.

Extreme sea levels at European coasts and their changes over the twentieth and twenty-first centuries are considered, including a method to analyze extreme sea levels and to assess their changes in a consistent way at different sites. The approach is based on using a combination of statistical tools and dynamical modelling as well as observational data and scenarios for potential future developments. The analysis is made for both time series of extreme sea levels and individually for the different components contributing to the extremes comprising (i) mean sea level changes, (ii) wind waves and storm surges and (iii), for relevant places, river flows. It is found that while regionally results vary in detail, some general inferences can be obtained. In particular it is found, that extreme sea levels show pronounced short-term and long-term variability partly associated with seasonal and nodal tidal cycles. Long-term trends are mostly associated with corresponding mean sea level changes while changes in wave and storm surge climate mostly contribute to inter-annual and decadal variability, but do not show substantial long-term trends. It is expected that this situation will continue for the upcoming decades and that long-term variability dominates over long-term trends at least for the coming decades.

A comparison study between 10 Mediterranean lagoons has been carried out by means of the 3-D numerical model SHYFEM. The investigated basins are the Venice and Marano-Grado lagoons in the Northern Adriatic Sea, the Lesina and Varano lagoons in the Southern Adriatic Sea, the Taranto basin in the Ionian Sea, the Cabras Lagoon in Sardinia, the Ganzirri and Faro lagoons in Sicily, the Mar Menor in Spain, and the Nador Lagoon in Morocco. This study has been focused on hydrodynamics in terms of exchange rates, transport time scale, and mixing. Water exchange depends mainly on the inlet shape and tidal range, but also on the wind regimes in the case of multi-inlet lagoons. Water renewal time, which is mostly determined by the exchange rate, is a powerful concept that allows lagoons to be characterized with a time scale. In the case of the studied lagoons, the renewal time ranged from few days in the Marano-Grado Lagoon up to 1 year in the case of the Mar Menor. The analysis of the renewal time frequency distribution allows identifying subbasins. The numerical study proved to be a useful tool for the intercomparison and classification of the lagoons. These environments range from a leaky type to a choked type of lagoons and give a representative picture of the lagoons situated around the Mediterranean basin. Mixing efficiency turns out to be a function of the morphological complexity, but also of the forcings acting on the system. Key Points Comparative study of 10 Mediterranean lagoons using a 3-D hydrodynamic model Characterization of flushing, mixing efficiency, and water renewal Classification of lagoons based on water renewal time and exchange rate © 2014. American Geophysical Union. All Rights Reserved.

A hydrodynamic model of the Venice Lagoon and the Adriatic Sea has been developed in order to study the exchanges at the inlets of the Venice Lagoon, a complex morphological area connecting the sea and the lagoon. The model solves the shallow water equations on a spatial domain discretized by a staggered finite element grid. The grid represents the Adriatic Sea and the Venice Lagoon with different spatial resolutions varying from 30 m for the smallest channels of the lagoon to 30 km for the inner areas of the central Adriatic Sea. Data from more than ten tide gauges displaced in the Adriatic Sea have been used in the calibration of the simulated water levels. After the calibration, the tidal wave propagation in the North Adriatic and in the Venice Lagoon is well reproduced by the model. To validate the model results, empirical flux data measured by acoustic Doppler current profiler probes installed inside the inlets of Lido and Malamocco have been used and the exchanges through the three inlets of the Venice Lagoon have been analyzed. The comparison between modeled and measured fluxes at the inlets outlines the efficiency of the model to reproduce both tide- and wind-induced water exchanges between the sea and the lagoon. Even in complex areas, where highly varying resolution is needed, the model is suitable for the simulation of the dominating physical processes.

The oceanographic forecast capability in coastal seas is often limited by the capacity of the numerical models in correctly reproducing the complex morphology of the coastline and the exchange processes between the shelf and the open seas. In the marginal Adriatic Sea this task is of uppermost importance due to the presence of several coastal water bodies and rivers. We present here a new operational oceanographic system, called Tiresias, based on the unstructured grid model SHYFEM and representing the whole Adriatic Sea together with the lagoons of Marano-Grado, Venice and Po Delta. The novelty of this oceanographic system resides in the very high-resolution, up to 10 m, of the numerical mesh, and in the high spatial and temporal resolution of the forcing and boundary conditions that drive the forecasts. The forecast results are evaluated against sea temperature and salinity profiles, mean circulation fields derived from a regional ocean model, tide gauges and drifter trajectory. The presented results highlighted the capacity of Tiresias in forecasting the general circulation in the Adriatic Sea, as well as several relevant coastal dynamics, such as saltwater intrusion, storm surge and riverine waters dispersion.