Search

Rock-sills are instream low-head structures generally used to stabilize the riverbed. Their presence causes the formation of pools and riffles along the river, thus improving the aquatic habitat and creating resting spots for aquatic species. In this study, the riverbed morphology due to the rock-sill configuration installed at river bends was experimentally analyzed under clear-water condition, with a uniform, granular bed material. Tests were conducted by varying the inclination of sills with respect to the radial direction in three curved bends. Experimental evidence confirmed that the curvature of the channel bend plays a fundamental role, i.e., scour features significantly differed from those occurring in straight channels. Likewise, the inclination of the sill and its shape affect the scour morphology. The presence of the sill and the curvature of the channel caused an asymmetric distribution of the flow in the radial direction, possibly resulting in a shift of the scour hole toward the center. The analysis of experimental data allowed us to provide practitioners with a useful formula to predict the maximum scour depth. Finally, interesting insights on scour dynamics and features at equilibrium are also presented. [ABSTRACT FROM AUTHOR]

A formula is proposed to determine the maximum reference pressure at the interface of the breakwater core and filter layer, based on small-scale physical model tests. Regular and irregular waves have been considered. It is found that the maximum reference pressure at the interface of the breakwater core and filter layer depends on the level of the water surface along the breakwater seaward slope. The proposed formula is verified using large-scale model results and real-scale field observations in non-overtopping and non-breaking wave conditions; it contains a nondimensional parameter that is a function of the wavelength and width of the core at a given water depth. [ABSTRACT FROM AUTHOR]

In this study, the effects of geometric parameters, such as the ramp roughness size and the ramp slope on the scour parameters downstream of block ramps, are experimentally investigated for different hydraulic conditions. Scour parameters, such as the maximum scour depth and length and the maximum ridge height and length, are evaluated. Experiments are conducted in clear water conditions (no sediment transport) for different gravel ramp slopes in which different critical flow depths and tailwater depths are examined. The results indicate that the maximum scour depth downstream of a block ramp for different bottom slopes is directly affected by the tailwater depth, independent of the critical flow depth; the scour depth decreases by increasing tailwater depth. A comparison of the results indicates that increasing the roughness of the block ramp leads to a reduction in the maximum scour depth. [ABSTRACT FROM AUTHOR]

This study starts from a two‐layer 1D Estuary Box Model (EBM), the so called Centro Euro‐Mediterraneo sui Cambiamenti Climatici (CMCC) EBM (Verri et al., 2020, https://doi.org/10.1016/j.ocemod.2020.101587), devised to offer a proper representation of the net river release in a coupled modeling framework with hydrology models and ocean models reaching the mesoscale. Two key advances are proposed in the present study: (I) the estuary length and (II) the horizontal eddy diffusivity coefficient are no longer considered as static parameters to calibrate but two non‐dimensional equations have been introduced in order to make them time‐variable. The Goro branch of the Po river delta is considered as case study of "salt‐wedge estuary" flowing into a microtidal sea. Regarding the estuary length, a non‐dimensional equation has been tested and validated. This equation provides a time dependent estuary box volume which is more realistic choice. This time‐variable estuary length represents the length of the salt wedge intrusion. Regarding the horizontal eddy diffusivity, the static eddy coefficient adopted in the previous version of the model is a coarse assumption. Thus a non‐dimensional equation for this coefficient has been tested and validated. It makes the eddy diffusivity dependent on the velocity shear, the salinity gradient and the estuary geometry. The proposed dynamic formula is found to enhance the model capability to reproduce the salinity at the estuary mouth. Overall the high statistical performance in terms of RMSE and correlation coefficient, the short CPU time and the minimal calibration encourage to use the CMCC EBM in coupled mode with both mesoscale‐resolving ocean and hydrology models to produce operational forecasts and climate scenarios. Plain Language Summary: The Centro Euro‐Mediterraneo sui Cambiamenti Climatici Estuary Box Model is placed in the framework of developing a conceptual and numerical modeling approach to simulate the effects of river release on the coastal to open sea circulation and dynamics. The few kilometers resolution of mesoscale ocean models cannot explicitly resolve the estuary dynamics; thus, the idea of an "estuary box model" that gives reasonable values of water volume flux and salinity at the river mouth, which in turn affects the ocean dynamics. A further development of the model equations is offered in this article and is demonstrated to enhance the model capability to reproduce the salinity at the estuary mouth; moreover, the length of the salt wedge intrusion is considered a model unknown. The research is not only interesting from an academic point of view but also for its practical application: (i) introducing an information on river release into ocean models, from regional to global scale, can improve their performance and produce more realistic operational forecasts or climate scenarios; (ii) introducing an estimate of the length of the salt wedge contributes to address the pressing issue of salt water intrusion and salinization processes in coastal areas. Key Points: An Estuary Box Model is devised to represent the salt‐wedge intrusion length and the net river release at the estuary mouthTwo key advancements, that is non‐dimensional equations for time‐variable estuary length and eddy diffusivity, enhance the model performanceThe proposed model is suitable for coupling with mesoscale ocean and hydrology models to produce operational forecasts and climate scenarios [ABSTRACT FROM AUTHOR]

A new prediction formula is proposed to determine wave-induced pore pressure height distribution inside the core of rubble-mound breakwaters. Existing observed field and experimental data in the literature have been examined, and a valuable database has been obtained. Using dimensional analysis, a new wave damping parameter has been derived. In comparison with the existing empirical Biesel's formula, the proposed prediction formula directly takes into account the influence of the mean diameter of the core material, water depth, and important wave parameters such as incident wave height and wavelength, and there is no more necessity to assume appropriate values for the seepage coefficient and the material coefficient that are essentially needed for Biesel's formula. The new prediction formula presented here has its merits in providing an alternative form and insight into the physics of phenomena. [ABSTRACT FROM AUTHOR]

Scour characteristics and morphologies downstream of rock sills due to channel curvature have been analyzed at the hydraulic laboratory of the University of Pisa. Two series of experiments have been conducted. The first series included tests on scour downstream of rock sills in straight channel. Three different channel bends with different lengths were studied in the second test series. All experiments have been carried out in clear water condition. The results showed that the tailwater depth plays an important role on scour characteristics. In addition, it was experimentally proven that the stream curvature affects the morphology and the maximum scour depth, i.e., an increase of the bend radius causes a decrease in the value of the maximum scour depth. Finally, three scour morphology types have been distinguished. Useful empirical relationships have been proposed in order to evaluate the main features of the scour geometry. [ABSTRACT FROM AUTHOR]

J-Hook Vanes are in-stream river grade-control structures to reduce stress along the outside of the river bends and to promote scour in the pools and improving the aquatic habitat. The main purpose of this study is to investigate the effect of the channel curvature on the scour hole characteristics and morphologies downstream of J-Hook structures. The main scour geometry parameters have been analyzed at the hydraulic laboratory of the University of Pisa. Three different channel bends were studied. All experiments have been carried out in clear water conditions. Scour morphologies were surveyed using 3D laser technology. The results showed that an increase of the bend radius causes a decrease in the value of the maximum scour depth. The observations showed that the channel curvature is an important parameter to classify the scour morphology and directly affects the position of the maximum scour depth. Finally, different scour morphology types downstream of J-Hook Vanes are formed. [ABSTRACT FROM AUTHOR]