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The South-East of Sicily is characterized by a complex system of coastal lagoons. The site, is considered of great naturalistic value, as it hosts a rich biodiversity and represents an important stop for bird species that migrates through the Northern European-African route. According to recent studies, the site is subject to an ever-increasing climate related coastal erosion and flooding risk, with an estimated potential land loss of 6.2 km2 by 2100 (Antonioli et al. 2020). In the present work, the effectiveness of a dune revegetation is investigated, in order to understand the role played by environmental restoration in reducing coastal risk. A SWAN+XBeach (Booji et al. 1996; Roelvink et al., 2009) numerical modeling chain is developed, aimed to simulating the hydraulic and transport processes that characterize a coastal area, in order to evaluate the effectiveness of the dune revegetation intervention. Results show a reduction of coastal flooding risk due to extreme wave events as an effect of the extended vegetated dune strip. Presence of the vegetation drastically improve coastal protection to the city area. Specifically, a reduction up to 42% of the flooded city area is observed. References Antonioli, F., Defalco, G., Moretti, L., Anzidei, M., Bonaldo, D., Carniel, S., ... & Schicchitano, G. (2019). Relative sea level rise and potential flooding risk for 2100 on 15 coastal plains of the Mediterranean Sea. In Geophysical Research Abstracts (Vol. 21). Booij, N., Holthuijsen, L.H. and R.C. Ris, 1996, The SWAN wave model for shallow water, Proc. 25th Int. Conf. Coastal Engng., Orlando, USA, Vol. 1, pp. 668-676. Roelvink, D., Reniers, A., van Dongeren, A., van Thiel de Vries, J., McCall, R., & Lescinski, J. , 2009. Modelling storm impacts on beaches, dunes and barrier islands. Coastal Engineering, 56(11-12), 1133-1152. doi:10.1016/j.coastaleng.2009.08.006

This work presents the results of an investigation on how wave overtopping at a near-vertical seawall at the back of a sandy foreshore is influenced by sequences of erosive storms. The experiments were carried out in the Large Wave Flume (GWK) at Leibniz University, Hannover (Germany). The tested layout consisted of a near-vertical seawall and a sandy foreshore with an initial slope. Three sequences of idealised erosive storms were simulated. Within each storm both the incident wave conditions and still water level were varied in time to represent high and low tide conditions. Each sequence started from a configuration and the beach was not restored in between storms. The measurements included waves, beach profile, wave overtopping volumes. The profile of the beach was measured after each sea state tested. Wave overtopping at each stage of the tested storms was significantly influenced by bed changes. This was linked to the measured evolution of the beach. Measurements showed that a barred profile developed quickly at the start of each sequence, and scour developed at the toe of the structure during high water level conditions, while accretion or partial backfilling developed during low water level conditions. Due to these processes, the position of a sea state in the tested sequence is shown to be an important factor in determining the wave overtopping volume. Remarkably, when a weaker idealised storm followed a more energetic one, nearly the same level of overtopping was recorded. This is explained by the foreshore erosion, leading to increased water depths and wave heights at the toe of the structure. This finding allows to quantify and to explain the variability of wave overtopping in storms following one another at intervals shorter than the recovery time of the foreshore. The work was supported by the European Union Horizon 2020 Research and Innovation Programme through the grant to HYDRALAB-PLUS, Contract no. 654110. We are grateful to all the staff in GWK for the hard work that made the experiments and analysis possible.

Coastal flooding is one of the most important natural hazards worldwide, increasingly growing in a changing climate. Various problems concerning the current and potential future risk of coastal areas, highlighting the needs for reliable forecast of storm conditions that can reach the coasts and of consequent estimated of the probability of flooding of urbanized areas.The study presented here aims to develop a method to predict flooding in coastal areas through Artificial Neural Networks (ANNs). The method was applied to the village of Granelli, in the South-Eastern part of Sicily (Italy). The present work was organized into two-phase: the first was dedicated to create the database of the flooded areas, through a physically-based modelling of wave propagation from offshore to the coast; the second was dedicated to study how to use the relate through machine learning approach onshore flooding results to offshore wave characteristics.As regards the first phase, the wave data used in the present study were obtained using two nested numerical models: SWAN and Xbeach. For an accurate simulation of wave propagation both in the nearshore zone and on the beach, a bathymetric survey of the submerged foreshore and a morphological survey of the emerged beach were carried out. The first one was surveyed through a Multibeam eco-sounder up to a depth of -12 m. The survey of the emerged beach was carried out using a Trimble TX8 Laser Scanner. As regards the boundary conditions, more than 1600 scenarios were simulated by changing both the offshore wave characteristics and the water elevation.During the second phase, the offshore wave characteristics and the resulting flooded areas were used to train several configurations of an ANN. After a calibration process of the ANN configuration, the best one was identified through comparison with the results of Xbeach.The proposed approach allows both to significantly reduce the time required for the estimation of flooding areas (8-9 hours required by Xbeach for each sea state against a few seconds required by ANN for the entire storm) and to obtain extremely reliable results with an accuracy of 0.05 m2 in terms of root mean square error.AcknowledgmentsThis work has been partly funded by the project “NEWS - Nearshore hazard monitoring and EarlyWarning System" (code C1-3.2-60) in the framework of the programme INTERREG V-A Italia Malta 2014-2020, by the project “ISYPORT - Integrated System for navigation risk mitigation in PORT” financed under the program PNR 2015-2020 and by University of Catania funded project "Interazione Moto Ondoso - Strutture (IMOS)".

An assessment of formulas to recover wave surface elevation from pressure measurements was carried out in the present study. The investigation focused on the formulas’ performance in the shoaling region, i.e. where the wave nonlinearity gradually increases as the wave travels towards shallower waters. Formulas based on linear wave theory alongside nonlinear reconstructions were considered. Experiments in a large-scale wave flume provided with a concrete beach profile were performed, in which regular waves were generated and surface elevation was measured with acoustic, resistive and pressure gauges. The considered formulas require the application of a cutoff frequency to the wave signal in order to avoid high frequencies amplification that progressively arise as wave shoaling occur. A simple but effective method to obtain a reference cutoff frequency is proposed in the present work; the method is based on a polynomial fitting of the unfiltered wave energy spectrum. A sensitivity analysis of each formula to the variation of this cutoff frequency was carried out. Results showed that all the investigated formulas recover wave elevation fairly well for low-nonlinearity waves, whereas overestimating wave crest height as nonlinearity increases. Wave reconstruction of the linear formulation performance was comparable to nonlinear formulations in terms of wave crest height reconstruction, although tending to amplify frequencies in the wave trough. Moreover, the performance of the formulas to correctly recover the asymmetry and flatness of the surface elevation distribution was assessed by analysing third- and fourth-order moment statistics. In this sense, nonlinear reconstruction formulas performed better in recovering the asymmetric distribution of the wave elevation, with the formula based on linear wave theory underestimating skewness and kurtosis for large nonlinearity waves. This work was funded by the projects: “ISYPORT - Integrated System for navigation risk mitigation in PORTs” funded under the PNR 2015-2020 program, REST-COAST - Large scale RESToration of COASTal ecosystems through rivers to sea connectivity (call: H2020-LC-GD-2020; Proposal no. 101037097) and “VARIO - VAlutazione del Rischio Idraulico in sistemi cOmplessi” of the University of Catania.

Coastal areas are characterized by a high level of risk because of its intrinsic vulnerability to the sea action and the high number of socio-economic activities as well as of marine habitats. Traditional methodologies for the design of coastal defences cannot be applied straightforward in the presence of the effects of climate change because of the need to take into account the non-stationarity of natural processes. A novel approach based on an integrated coastal zone management is required to counteract the main consequences of global warming effects in coastal areas (i.e. sea level rise and the increase in frequency and magnitude of extreme events). In particular, besides institutional measures and preparedness and prevention actions, also structural intervention should be implemented. First of all, the upgrade of existing coastal defence structures should be considered, where this strategy is technically and economically feasible. In addition, it is suggested the realisation of Nature-Based Solutions, which consist on using natural processes to create a resilient system. Finally, the integration of traditional and innovative techniques for the design of coastal defences to realise resilient or, even better, antifragile systems is the most preferable approach. Indeed, perfect knowledge of future conditions is not needed for the design of antifragile systems, since this kind of structures are able to improve themselves when hit by unexpected events.

In the present work, an investigation on the hydrodynamics of waves and currents interacting at right angle over rough beds has been carried out. The work focuses on the effects of wave motion superposed on the current steady boundary layer, and on how the oscillatory flow affects the current velocity distribution, in the presence of gravel and sand beds.A laboratory experimental campaign on wave-current orthogonal interaction has been carried out in a shallow water basin at DHI Water and Environment (Hørsholm, Denmark).Mean flow has been investigated by computing time- and space-averaged velocity profiles. Friction velocity and equivalent roughness have been inferred from the velocity profiles by best fit technique, in order to measure the shear stress experienced by the current mean flow.Tests in the presence of only current, only waves and combined flow have been performed.Instantaneous velocities have been Reynolds-averaged to obtain turbulent fluctuations time series and compute turbulence related quantities, such as turbulence intensities and Reynolds stresses.The analysis of the mean flow revealed a complex interaction of the waves and currents combined flow. Depending on the relative strength of the current with respect to the waves, the superposition of the oscillatory flow may determine an increase or a decrease of the bottom friction experienced by the current.The superposition of waves always induces an increase of turbulence intensity, except over gravel bed in which a decrease is observed in the very proximity of the bottom. Over gravel bed, the presence of the oscillatory flow determines a decrease of the turbulent intensity gradient, which may be related to the decrease of bottom friction observed in the mean flow analysis.A turbulence quadrant analysis has been performed and showed that, in the presence of a lone current over a flat gravel bed, the turbulent ejection-sweep mechanism reaches parts of the water column closer to the water surface, similar to what has been observed in the turbulence intensity profiles.The superposition of the oscillatory flow appears to induce an increment of ejections and sweeps intensity, which is associated with the shear stress increase at the bottom observed in the mean flow analysis. Moreover, a decrease of the number of ejection and sweep events has been recorded, which suggests a suppression of the ejection-sweep events alongside an enhancement of their intensity.

The aim of this study was to assess the skeletal and dentoalveolar changes obtained after 1 year of treatment with elastodontic appliances (EA) in a retrospective cohort of children reporting early signs of malocclusion. Also, a detailed description of the tested EAs was reported. The study sample included 20 subjects, 8 males and 12 females, with a mean age of 8.4 ± 0.6 years, and a control group consisting of 20 subjects, 9 males and 11 females, with a mean age of 8.1 ± 0.8 years. All subjects in the treated group received the AMCOP second class (SC) (Ortho Protec, Bari, Italy) device. Digital impressions were taken along with a digital bite registration in centric relation before treatment (T0) and after 1 year (T1). Lateral cephalograms were also taken at T0 and T1 and cephalometric analysis was performed to assess the skeletal sagittal changes of the maxilla and the mandible (sella, nasion, A point angle, SNA^, sella, nasion, B point angle, SNB^, and A point–nasion–B point angle, ANB^) as well as the changes of the inter-incisors angle (IIA^). In the treated group, the distribution of subjects according to the presence of crowding and the pattern of malocclusion changed at T1. In the same group, there was an increase of subjects showing no signs of crowding and a class I occlusal relationship, while in the control group, there was a small increase of subjects developing dental crowding and featuring a worse sagittal relationship (class II) compared to pre-treatment condition. A statistically significant reduction of the overjet and overbite was recorded in the treated group between T0 and T1 (p &lt, 0.05), in the control group, a slight increase in the overjet and overbite was detected at T1, being this increment significanct only for the latter parameter. In the tested group, no significant differences were found between SNA^ values detected at T0 and T1 (p &gt, 0.05), instead the SNB^, ANB^, and IIA^ showed a significant increase after 1 year of treatment (p &lt, 0.05). From a clinical perspective, all clinical goals were reached since patients showed remarkable improvements in overjet, overbite, crowding, and the sagittal molar relationship. Within the limitations of the present study, EAs could be effectively used for the interceptive orthodontic in growing patients.

Archaeological sites are extremely vulnerable to the impacts of weather-related events, which may lead to irreparable damages to cultural heritage. Here an assessment of the debris-flow hazard for the UNESCO site of Roman Villa del Casale (Italy) is carried out, through a combination of historical analyses, field surveys, geomorphological and hydrological investigations and two-dimensional hydraulic numerical modelling, all performed at river catchment scale. Historical analyses reveal that the site has been hit by several landslides in the far and recent past. This is presently confirmed by the high level of exposure to the impact of rain-triggered debris-flow events, due to the position of the Villa at a closure section of the related river basin and to the hydro-geomorphological characteristics of the basin itself. By applying the proposed approach, a scenario analysis is carried out. Results allow one to highlight the dynamics of the impact of debris flows, thanks to space and time-dependent maps about deposition areas, water depth and speed values, and to identify the most vulnerable archaeological elements within the study site. The numerical simulations are also used to test the efficiency of the existing hydraulic defense systems and to support the implementation of an early warning system for the site protection. Here, we also synthetize the design of the architecture of the wireless monitoring network, the sensor technology adopted to develop an effective real time environmental monitoring system and management platform, to construct a Wireless Sensor Network (WSN) - early warning and reporting system, which can be applied as a prevention measure.

An effective system for forecasting coastal flooding due to wind waves is essential to prevent coastal risks. The forecast data provided by national and international agencies (i.e., ECMWF, NOAA, etc.) represent only the offshore condition and therefore additional numerical models, which take into account the several phenomena occurring in the nearshore area, must be implemented to correctly assess the risk of coastal flooding. Unfortunately, such models require high computational costs, which are often too demanding and not viable for large scale forecasting system. In this context, this paper presents the development of an Artificial Intelligence approach which allows for a fast prediction of the coastal flooding due to waves. Here, Artificial Neural Networks (ANNs) are proposed. The ANNs are fed with the offshore wave data and provide the wave setup and the wave runup on the beach. The application is conducted for the village of Santa Maria del Focallo, which belongs to the municipality of Ispica, in the Southeast side of Sicily. The preliminary validation of the adopted approach is promising although further tests must be conducted.

Breakwaters play a crucial role in the protection of coastal zones. Their maintenance is critical to safeguard the daily activities of harbours and marine areas. The evaluation of damage is a necessity for timely preservation works. Traditional monitoring methods span various techniques, ranging from mechanical profilers to optical systems. Current methods though are expensive, requiring remarkably sophisticated technologies which demand a high degree of expertise to be operated. In this paper, we propose an affordable yet accurate fully automated method based on 3D cameras. Our technique is non invasive, allowing hence non intrusive as well as fast measure of damage over time, simultaneously above and below sea water level. Experimental results obtained on laboratory breakwater models demonstrated that the proposed point cloud method, which does not depend on the imaging sensor and can be applied to any 3D dataset of rubble mound breakwater, can achieve accurate damage estimation, even when using a budget RGB-D camera. One of the additional advantages of using RGB-D cameras is the possibility to obtain measurements also in the presence of water.

Effects of surface waves on gravity current propagation are studied by means of a numerical model. The adopted modeling approach couples a Boussinesq-type of model for surface waves and a gravity current model for stratified flows. In particular two different turbulence closure models are introduced which take into account subgrid turbulence and an additional depth-constant eddy-viscosity. The turbulence parameters are calibrated by means of experimental data on the time evolution of the heavy front, obtained both in the absence and in the presence of regular surface waves. Velocity fields, heavy and light front position, shear stresses, vorticity and entrainment calculated by the model are analyzed. The turbulence closure which includes both uniform and Smagorinsky type eddy viscosity allows a better description of the actual gravity current propagation. In particular, the results highlight the fact that the presence of the oscillatory motion causes, simultaneously, a reduction in turbulence and an increase in the mixing of heavy and light fluids. Such a result is in agreement with the experimental observations.

An experimental study of wave and current interaction over ripples is presented in this paper. The campaign was carried out at the shallow water tank at the Danish Hydraulic Institute (DHI, Denmark), in the framework of the TA WINGS (Waves plus currents INteracting at a right anGle over rough bedS), funded by the European Union (EU) through the Hydralab+ program. Mean velocity profiles, measured with acoustic Doppler velocimeters for different flow conditions including current only, wave only and wave plus current were recorded and allowed to recover flow and vorticity fields. Recirculating cells in both wave only and wave plus current conditions form but they flatten when the current superposes over the wave. It was found that the superposition of current reduces the undertow present in the case of only waves and leads to an increase of vorticity outside the boundary layer. Instead, inside the boundary layer, the vorticity is dumped by the effect of current.

Most of the worldwide historical coastal and harbor structures have been severely damaged by extreme sea storms during their lifetime and hence need to be upgraded, also considering the effects of climate change (Hughes, 2014). Physical modelling is identified as the only feasible approach for the optimization of the upgraded structures, because of the existence of few studies concerning such an issue and the lack of specific design formulae (Burcharth et al. 2014; Croeneveld et al. 1984; Lara et al. 2019; Foti et al. 2020). Therefore, a novel general methodology for the design of upgrading solutions for existing breakwaters based on physical modelling is presented, considering the case study of the Catania Harbor breakwater. The results of the systematic extensive experimental campaign on possible solutions for upgrading the Catania harbor breakwater led to some general practical findings, which can be useful for the design of restoration options for existing breakwater at end of their lifetime.

The wave loads on a navigation lock gate provided with an opening in the ballast tank are analyzed using a mathematical model based on the linear wave theory and the numerical integration of the Navier-Stokes Equation. The analysis focuses on the evaluation of the non-linear effect influence on the vertical load on the gate. It is shown that the numerical and analytical models agree on the identification of the value of the wave number at which the maximum value of the dimensionless vertical force on the gate is detected. However the analytical model overestimates the peak value of the vertical load with respect to the CFD simulation. To fill this gap, in this paper an easy to use procedure is developed which allows to correct the results of the analytical model.

In the present work, an investigation on the hydrodynamics of wave-current orthogonal combined flow has been carried out. The work focuses on the effects of the oscillatory flow superposed on the current steady boundary layer, and on how the oscillatory flow affects the current velocity distribution. A laboratory experimental campaign of wave-current orthogonal interaction has been carried out in a shallow water basin at DHI Water and Environment (Horsholm, Denmark), in order to investigate the orthogonal combined flow in the presence of different roughness beds. Mean flow has been investigated by computing time- and space-averaged velocity profiles. Friction velocity and equivalent roughness have been inferred from the velocity profiles by best fit technique, in order to quantify the shear stress experienced by the current mean flow. Tests in the presence of only current, only waves and combined flow have been performed. Instantaneous velocities have been Reynolds-averaged in order to obtain turbulent fluctuations time series and compute turbulence related quantities, such as Reynolds stresses. The mean current velocity profiles have been also compared with a selection of analytical models in order to assess their validity for the case of wave-current orthogonal flow for the considered wave and current condition ranges. The analysis of the mean flow revealed a complex interaction of the waves and currents combined flow. Depending on the relative strength of the current with respect to the waves, the superposition of the oscillatory flow may determine an increase or a decrease of the bottom friction experienced by the current. Such a behavior is also strictly related to the bed physical roughness. Analysis of the turbulence Reynolds stresses seems to confirm the results of the mean flow investigation.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/GbtOgeLlVTU

The research is focused on the development and on the assessment of a measurement technique for bottom shear stresses. In particular, the wall–fluid interaction is analyzed adopting ferrofluids and using an optical readout system. The principle of operation of this technique is based on the capability of ferrofluids to react to external magnetic field changing their shape and their viscosity. The proposed magneto-rheological sensor, consisting in a magnetized drop of ferrofluid located at the channel bottom, is exposed to different flow conditions and its deformations are video-recorded. Thanks to the application of image analyses processes, the relation between shear stresses and magneto-rheological sensor deformation is investigated. The assessment of the measuring technique is carried out in the presence of different sandy bottoms and by considering several hydraulic (steady current) conditions. The range of measured bottom shear stress is 0.01–0.20 N/m$$^2$$. Tests carried out with different sandy bottoms characterized by different roughness provide insights about the high sensitivity of the sensor, which is able to detect slight changes in the sandy bottom mixture (less than 10$$\%$$ concentration in volume). Statistical analysis on the ferrofluid deformation shows that the sensor deformation is strictly related to the local hydrodynamics. For higher Re number we observed larger mean displacement in the direction of the flow and bigger oscillations. Power spectral densities of the ferrofluid displacement and of the velocity fluctuations measured at the ferrofluid apex point show how the two signals are characterized by the same slope in log–log graph for intermediate and high frequencies (> 0.2 Hz) representative of small-scale eddies.

In the present work, an experimental investigation on the hydrodynamics of shoaling waves superposed on a steady orthogonal current is carried out. An experimental campaign in a wave tank has been performed, with waves and current interacting at a right angle over a sloping planar beach. Velocity data have been gathered during the experiments in order to investigate mean, phase and turbulent flow. A detailed preliminary analysis of the time- and space-variability of the experiments is presented. Results show that a complex interaction between waves and current occurs as the wave shoals, in terms of sheer production, momentum transfer and turbulent mixing. Superposition of waves determines a shear increase at the bottom due to an enhanced turbulence mixing, nonetheless as depth decreases and the current velocity consequently increases, shoaling waves may be less efficient in enhancing shear at the bottom. Moreover, the superposition of waves determines the current to oscillate around its mean velocity value. Nevertheless, as wave shoals and simultaneously current velocity increases with decreasing depth, waves and current oscillatory motion experience a phase lag, as a response of the larger momentum of the current to the changing of the shoaling waves acceleration distribution along the wave phase. Moreover, the turbulent bursting events of the combined flow in proximity of the bed have been investigated by means of quadrant analysis, showing an increase of the turbulent ejections and sweeps due to the superposition of the shoaling waves.

An effective system of coastal flooding forecasting in the case of storm is essential to mitigate coastal risks for the population living in low-land coastal zones (less than 10 m above MSL). Nowadays, predictions of coastal flooding are usually carried out by adopting nested numerical models. However, the models adopted to obtain the data in the nearshore area require high computational costs, which are often too demanding and not viable for large scale forecasting. Data-driven models, such as Artificial Neural Networks (ANNs) can help to solve the problem as they can map complex nonlinear relationships between input and output variables once a suitable dataset of process realizations is available. In the present study a forecasting model for coastal flooding based on ANNs, in which the input data are the offshore wave characteristics from large scale model and the output results are the flooded areas, is proposed. These outputs provided a straightforward prediction of the area interested by coastal flooding during storms. Here an application of the model to assess the flooding risk in the village of Granelli, in the Southeast of Sicily (Italy) is presented.

Orthogonal wave-current interaction often occurs in coastal regions, when waves approach the shoreline near-orthogonally and longshore currents are present. Notwithstanding its wide relevance, this phenomenon is far from being understood to a full extent, especially in the presence of bed roughness. Indeed the effects on the apparent roughness due to the combination of steady currents and surface waves propagating at right angles are still a matter of debate, both in the current and in the wave dominated cases. To this aim, the hydrodynamic effects of an orthogonal regular wave on a current propagating over a rough bed were investigated; two different rough beds, one sandy and one made of gravel, were considered. Both surface elevation and velocity profiles were acquired by means of an array of wave gauges and Micro Acoustic Doppler Velocimeters positioned within the tank. Here the range of the investigated parameters was significantly enlarged with respect to the existing literature studies. The present paper focuses on the analysis of the mean velocity profiles. More specifically, observation of velocity profiles shows that the current to wave velocity ratio and the bed roughness play an important role, by impacting the value of the apparent roughness. Indeed it was found that as far as the flow is current dominated the addition of waves on the current increases the flow resistance. The opposite happens when the flow is wave dominated, irrespective of the bed roughness type. In particular, the apparent roughness increases as far as the wave plus current to current only friction velocity ratio increases. The increase is more rapid if the wave plus current prevails on the current only friction velocity.

The results of a new experimental campaign on an Overtopping BReakwater for Energy Conversion (OBREC) device are presented. Previous 2D model tests carried out at Aalborg University (DK) made it possible to define new prediction methods that were used to design the first OBREC prototype breakwater which has been operating at Naples Harbor (Italy) since January 2016. The new tests were carried out at the Hydraulic Laboratory of the Catania University aiming to provide reliable methods for evaluating the energy extracted by the device. In particular, the new tests investigate the probability distribution of the individual overtopping volumes which enter the OBREC reservoir. The methods presented and validated here allow for a reliable estimate of the time distribution of the input flow, which along with the characteristics of the device, can be used to predict the energy produced by OBREC devices.

New technologies provide a new great source of information, increasing the available knowledge in many different fields, including hydrology. With this work we wish to share with the Hydroinformatics community an attempt in the direction of using the social media to increase the general understanding of the areas affected by flooding events in Italy. We have developed “Floodbook”, an online platform aimed at constituting a database for flood-damaged areas in Italy, trying to fill the knowledge gap of flood events occurring in small and ungauged basins. The platform invites citizens to contribute posting geotagged contents, photos or videos, on the social media; these contents are collected and elaborated to provide a clear, yet rigorous and comprehensive, picture of the event. Some case studies are described to show how this data collection can be used to improve flood extent assessment and flood dynamics reconstruction.

A novel direct measurement strategy of wave near-bed velocity and bottom shear stress based on the use of ferrofluids is presented. The proposed methodology is aimed at overcoming some of the limits of state-of-the-art instruments, for use in presence of both surface waves and sediments. An inductive readout strategy is proposed to sense displacements of the ferrofluid spike over the inductive circuit due to the flow. Experimental tests have been performed in a wave tank both in hydrostatic conditions and in the presence of regular linear waves corresponding to deep and intermediate water depth cases. Obtained results indicate the applicability of the proposed strategy also in the presence of suspended load (either moderate or intense) and of a moderate bed load transport.

Wave–current flow over a bottom covered with different roughness elements was analysed to provide new insights into the statistical properties of the near-bed velocity. Experimental data of three different experimental campaigns, with orthogonal waves and currents over a sandy bed, a gravel bed and a rippled bed were used. Velocity profiles were acquired by means of a micro-ADV. The paper focuses on the effects that the waves have on the statistics of the velocity in the current direction. In particular, in the case of a steady current only, the near-bed velocities closely follow a Gaussian distribution. When waves are added, the distribution becomes double-peaked. In order to get single-peaked velocity distributions the total velocity events in the current direction were split in two classes according to the sign of the wave directed velocities. The nature of the distribution functions is influenced by the mass conservation principle and, in the rippled bed case, by the vorticity dynamics.

Large scale tests were performed in the large scale facility GWK at Hannover, Germany, within the HYDRALAB+ project ICODEP: Impact of Changing fOreshore on flood DEfence Performance. The test set-up consisted of a relatively steep 1:15 sandy beach profile in front of a battered seawall with 10:1 slope (almost vertical). Two storms were generated, S1 and S2 with for each storm a specific combined surge and tide profile with varying wave conditions (sea states) depending on water level. These two types of storms have been modelled in varying order, giving three types of storm clusters (C1, C2, and C3). After each sea state the foreshore profile was measured and during each sea state wave conditions as well as wave overtopping have been measured. The changing foreshore showed a breaker bar formation as well as scour or accretion directly in front of the battered wall, depending on water level.

An innovative measurement technique is proposed for investigating shear stress at sandy bottoms. This technique is based on the adoption of a ferrofluidic sensor and of an optical readout strategy. An experimental campaign is carried out for evaluating its performance. Experiments differ for the ferrofluidic sensor configuration (difference in the magnetic field) and for the bottom configurations (fixed bed or sandy bed). Calibration of the ferrofluidic sensor for the range of the investigated hydraulic condition and of the controlling magnetic field is presented. The ferrofluidic technique is promising when applied at sandy bottoms, as neither adhesion processes between sand grains and ferrofluid or influence of impacts of grains on the measurement are observed. In particular, the preliminary measure performed indicated that the ferrofluidic sensor is capable of sensing the different bed roughness.

Debris flow injections from tributaries into a main mountain stream generate deposits of sediments which, in turn, result in obstruction and eventual damming of the river section. This contribution presents the results of a series of flume experiments on the dynamics of these deposits, with reference to three different types of blockage: no blockage, partial blockage, and full blockage. Results show that the shape of the deposit is mainly controlled by the ratio between the debris flow discharge and the main river discharge. The experimental dataset is used to develop a deposit resilience stability index based on the shape of the deposit contour retrieved from photos taken from above. The proposed index is based on the invariant elliptic Fourier coefficients and the dimensionless transverse obstruction parameter. The elliptic Fourier coefficients give information on the symmetry of the deposit contour. High symmetry indicates more stable and resilient deposits. The proposed index is calibrated on the basis of the flume experiments and tested with field data. The results are quite promising and suggest that the index can be appropriate for a fast hazard assessment of multiple debris flow deposits at a regional scale.

A novel direct measurement strategy of bottom velocities and shear stresses based on the use of ferrofluids is presented. Such a strategy overcomes some of the limits of state-of-the-art instruments. A preliminary experimental campaign has been carried out in the presence of currents in steady flow conditions in order to test the effects of ferrofluid quantity and of the controlling permanent magnetic force. An alternating current (AC) circuit and a direct current (DC) conditioning circuit have been tested. For velocities larger than 0.05 m/s, the near-bottom velocity-output voltage calibration curve has a monotone parabolic shape. The sensitivity of the instrument is increased by a factor of 30 when the DC circuit is used.

The propagation of gravity currents is analyzed in the presence of regular surface waves, both experimentally and numerically, by using a full-depth lock-exchange configuration. Full-depth lock-exchange releases have been reproduced in a wave flume, both in the absence and in the presence of regular waves, considering two fluids having densitiesρ0ρ0andρ1ρ1, withρ0

This paper presents the results of an experimental investigation of the backfilling of scour holes around circular piles. Scour holes arounda pile aregenerated either by a current or a wave.Subsequently, the flow climate is changed from current to wave, combined waves and current, or wave to a smaller wave, leading to the backfilling of the scour hole. The investigation has shed light onto the mechanism behind the backfillingprocess.Theresultsshowthatthescourdepthcorrespondingtotheequilibriumstateofbackfillingisthesameasthatcorrespondingto the equilibrium state of scour aroundthepilefor thesame wave (or combined waves and current) climate. The time scale of backfilling hasbeen determinedasafunctionofthreeparameters,namely,(1)theKeulegan-Carpenternumberoftheinitialwaveorcurrent(whichgeneratestheinitial scourhole);(2)thatofthesubsequentwave,whichbackfillsthescourhole;and(3)theShieldsparameterassociatedwiththelatterwave,forlive- bedconditions.Inthecaseofthecombinedwavesandcurrent,thecurrent-to-wave-velocityratioisalsoinvolved.Thetimescaleofthebackfilling process is completely different from that of scour. The time scale of backfilling is much larger than that of scour when the Keulegan-Carpenter numberassociatedwiththebackfillingisKCf ,Oð10Þ(typicalwindfarmapplication),whilethetimescaleofbackfillingcanbesmallerthanthat of scour when KCf ..Oð10Þ. DOI: 10.1061/(ASCE)WW.1943-5460.0000161. © 2013 American Society of Civil Engineers. CE Database subject headings: Scour; Piles; Offshore structures; Currents. Author keywords: Backfilling; Scour; Pile; Offshore windfarm; Offshore wind turbine; Waves; Current; Time scale.

Hydrodynamics of full depth lock exchange gravity currents is investigated by means of a numerical model which takes into account both surface wave propagation and gravity currents. The adopted modeling approach couples a Boussinesq-type of model for surface waves and a gravity current model for stratified flows. Such a model is calibrated by means of experimental data, obtained both in the absence and in the presence of surface regular waves. The model provides a fairly good prediction of the heavy front position in time in both conditions. Velocity fields, heavy and light front position, turbulence and vorticity distribution are also analyzed. In particular, results highlight the fact that the presence of the oscillatory motion causes a reduction of turbulence and of mixing between heavy and light fluids.

A comparison between a range of transfer functions to recover wave height from pressure sensors data is presented. The analysis is carried out by means of a large-scale wave flume experimental dataset, in which resistive, acoustic and pressure gauges recovered wave height are compared as the waves travel from intermediate waters, to the shoaling region and finally into the surf zone. All the considered transfer functions result adequate in recovering wave height in intermediate waters, becoming gradually less accurate as the steepness of the wave increases in the shoaling region and in the surf zone. The accuracy of the compared transfer functions is assessed by means of an ensemble wave height based deviation.

Breakwaters are marine structures useful for the safe harbouring of ships and the protection of harbours from sedimentation and coasts from erosion. Breakwater monitoring is then a critical part of coastal engineering research, since it is crucial to know the state of a breakwater at any time in order to evaluate its health in terms of stability and plan restoration works. In this paper we present a novel breakwaters monitoring approach based on the analysis of 3D point clouds acquired with RGB-D cameras. The proposed method is able to estimate roto-translation movements of the Accropodes, building the armour layer of a breakwater, both under and above still water level, without any need of human interaction. We tested the proposed monitoring method with several laboratory experiments. The experiments consisted of the hitting of a scale model barrier by waves in a laboratory tank, aiming to asses the robustness of a particular configuration of the breakwater (that is, the ar rangement of the Accropodes building the structure). During tests, several 3D depth maps of the barrier have been taken with a RGB-D camera. These point clouds, hence, have been processed to compute roto-translation movement, in order to monitor breakwater conditions and estimate its damage over time.

The erosion process caused by fluid action in rivers, in near-shore regions, and around offshore platforms is interesting for both environmentalists and engineers. Many studies have been made of this phenomenon. However, sediment transport processes are still far from being clearly understood. Field and laboratory investigations are extremely important for improving our knowledge of the basic forces that control such phenomena. Many difficulties arise when trying to measure erosion or scouring processes. One of the most important features of the measurement system is that the instrumentation should not disturb either the fluid motion or the sediments. Therefore, the scour due to the wave motion around a vertical pile is investigated because of the equilibrium conditions of the erosion process. Techniques for structured light and image acquisition can measure and recover sand bed evolutions. These techniques are noninvasive and provide visual reference points or lines on the bottom during morpho-dynamic evolution. This study used computer vision techniques, based on the use of structured light, for three-dimensional (3D) measurements of the flow-sediment interactions with piers. Extensive laboratory applications have been made in wave flumes and wave tanks for investigating the erosion processes around a vertical pile or for investigating small-scale bedforms formation. These methods can detect changes of the sandy bottom, such as small bed-forms or scours, with great accuracy without interfering with the measured system. They also can observe the dynamic behavior of these morphological features.

In this work, experimental and numerical results relative to gravity currents are presented. Gravity currents are realized by means of lock exchange release experiments in the presence of surface waves. Experiments have been carried out in a laboratory flume equipped with a wavemaker at one end and an absorbing beach at the other end. The region comprised between the wavemaker and the lock has been filled with salt water, while the remaining part of the channel has been filled with fresh water. At time t=0 the lock was lifted and at the same time the wavemaker was turned on, generating a sinusoidal surface wave. The evolution of the experiment was filmed and the shape and the front position of the gravity current were gathered. Numerical results have been obtained by means of a two-layer shallow water Lattice Boltzmann model and compared to experimental results. The agreement has been found fairly good, both confirming that the Lattice Boltzmann Method is a versatile tool in simulating two-layer shallow water flows and highlighting the dynamics of the flow as a whole.

The propagation of spilling waves interacting with complex bathymetries was studied by means of a new two-dimensional weakly dispersive, fully nonlinear Boussinesq-type of model. In particular, the governing equations were derived assuming the flow as rotational, and the effects of vorticity due to breaking were included through the surface roller concept, which was defined and implemented on the basis of a new algorithm developed for the purpose. The propagation of vorticity, due to wave breaking, is estimated under the assumption that the effect of convection is leading order with respect to the effect of vorticity-stretching and that the breaking phenomenon does not show high curvature on the horizontal plane. In particular, the dynamic problem is decoupled in a lateral direction considering a series of separated sections in which vorticity is solved. In this way it is possible to obtain rotational information along the domain to a reasonable computational cost. The numerical model was validated in a simple one-dimensional case and then applied to the study of breaking-generated vorticity due to wave motion over a submerged shoal.