J-Hook Vanes are in-stream river grade-control structures to reduce stress along the outside of the river bendsc and to promote scour in the pools and improving the aquatic habitat. The main purpose of this studyc 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.

Stream deflectors are in-stream hydraulic structures that limit the flow channel width, thereby accelerating the flow through the constricted section. Single-wing and double-wing log deflectors are the two most commonly used types of in-stream eco-friendly structures. The purpose of this paper is to investigate the scour phenomena downstream of log deflectors in straight horizontal channels. The main goal is to obtain design equations to predict the main scour parameters and describe the scour morphology. All the experiments have been carried out in a horizontal channel and in clear water conditions. Log deflectors with different heights and angles were tested. Different hydraulic conditions including densimetric Froude numbers, water head drops, and tailwater values were studied. Results show that the tailwater depth and deflector angle are important variables to determine the scour parameters. Dimensional analysis leads to design equations to estimate the maximum scour depth, maximum length of the scour, and maximum height and length of the dune. Two types of scour morphology downstream of log deflectors have been defined.

Low-environment impact structures have the advantage to conjugate both hydraulic functioning and environmental care. In particular, these structure typologies are widely used for river restoration both to control sediment transport and to dissipate flow energy. In the present paper, rock grade control structures, stepped gabion weirs, block ramps, and cross-vane weirs are analyzed and compared. Both similitudes and differences in terms of scour characteristics and dissipative efficiency are highlighted. The comparison shows that block ramps are the most efficient structures among those tested. Useful practical relationships are proposed in order to estimate both scour characteristics downstream of each structures and energy dissipation.

In-stream grade-control hydraulic structures have been employed to reinstate riverbeds, to protect riverbanks, and to improve aquatic habitats. This paper aims to study scour phenomena and morphologies downstream of cross-vane structures installed in curved channels, and structure orientation with respect to the flow direction. Experiments have been conducted in clear-water conditions. The results showed the important effect of the channel curvature on the maximum scour depth value and position.Increasing of the bend radius leads to a decrease in the value of the maximum scour depth. The scour morphology has been classified in three types. Observations showed that the scour typology affects the maximum scour depth value. The variation of the structure orientations has been experimentally analyzed and results showed a significant effect on the maximum scour depth position.

River restoration aims to improve physical natural form and processes of a river. Techniques to control the riverbed, stabilize channel alignment, protect stream banks, and rebuild the natural habitat are an important part of river restoration projects. Rivers can be stabilized and habitat restored through techniques such as rebuilding meanders and pool-riffle sequences and managing large wood. Structures that limit channel width to accelerate the normal flows through the constricted section are referred to as stream deflectors. Single-wing, double-wing and triangular deflectors are the most commonly used types of this measure. Log-frame deflectors consist of a triangular log frame filled with rock. Deflector constructions singly or in series in low gradient meandering streams, divert base flows toward the center of the channel and, under certain conditions, increase the depth and velocity of flow thereby creating scour pools and enhancing fish habitat. Scour characteristics and morphologies downstream of log-frame deflectors have been analyzed at the hydraulic laboratory of the University of Pisa. All experiments have been carried out in clear water conditions. The results showed that the tailwater depth plays an important role on scour characteristics. In addition, it was experimentally proven that using log-frame deflectors instead of log-deflectors result in a better river bank protection. In this case, for all the tested hydraulic conditions, the scour hole never occurred close to the channel bank. Useful empirical relationships have been proposed in order to evaluate the main features of the scour geometry.

Log-Vane is a grade-control structure of common use to stabilize river bed and river banks. The purpose of this paper is to study the scour phenomena downstream of Log-Vanes in straight rivers. The main goal is to obtain design equations to determine the main scour parameters and the scour morphology. All the experiments have been carried out in a horizontal channel and in clear water conditions. Log-Vanes made of wood, with different heights and vane angles, were tested. Different hydraulic conditions including densimetric Froude numbers, water drops and tail water values were tested. Results show that the tail water depth is an important variable to determine the maximum scour depth. The vane angle results to be an important parameter to predict the scour parameters. Dimensional analysis allows to derive design equations useful to estimate the maximum scour depth, maximum length of the scour and maximum height and length of the dune.

River restoration structure’s design features are some of the most important topics for hydraulic engineers. These low-environmental impact structures minimize the impact on natural contexts and at the same time, they do not require frequent anthropic intervention. Generally, these structures are used for river restoration and represent a dynamic system for both river grade-controlling and improving the aquatic habitat. The present paper aims to compare scour downstream of two different low-head rock made control structures; cross-vane and W-weir. The analysis involves the results of laboratory experiments conducted at the PITLAB hydraulic laboratory of University of Pisa and a detailed comparison of scour hole characteristics, highlighting similitudes and differences in the respective ranges of application. All tests are done in clear water conditions using uniform sand as channel bed material.

Nowadays stream restoration structure’s design features is an active field of research for river engineers. Low-environmental impact is the main characteristics of these types of structures in needless of frequent human interventions during the operation. These structures are used for riverbank protection, river grade controlling and improving the aquatic habitat. This study aims to compare scour downstream of two different low-head grade-control structures; Log-Vane and Log-Deflectors. The analysis contains the results of laboratory experiments conducted at the hydraulic laboratory of the University of Pisa and a detailed comparison of scour hole characteristics, highlighting similitudes and differences in the respective ranges of application. All tests have been done in clear water conditions using uniform sand as channel bed material.

J-Hook vanes are grade control structures used to stabilize the riverbed. This paper aims to investigate the behaviour of J-Hook vanes as a grade-control structure in straight rivers. Scour downstream of J-Hook vane structures like other grade-control structures depends on the shape of the structure and the river hydraulic conditions. The purpose of this study is classifying the scour geometry and predicting the main scour parameters such as the scour depth, length, width, and the ridge height and length downstream of the J-Hook vanes in straight rivers. Experiments were carried out in a horizontal channel. For each length of the structure, three heights in different hydraulic conditions, including densimetric Froude numbers, water drops, and opening ratios, were tested. Results show that the densimetric Froude number, the drop height, and the height of the structure are the key parameters to form and classify the scour. Equations have been derived using dimensional analysis and experimental data to predict the maximum scour depth, the maximum length of the scour, the maximum scour width, and the maximum height and length of the dune. All the experiments were conducted in clear water conditions.

Cross-Vanes are hydraulic structures used to stabilize the riverbed and control the grade for river restoration. Scour downstream of CrossVane structures depends on the shape of the structure, the bed material and the river hydraulic conditions. This paper aims to predict the maximum scour depth and classify the scour morphology. Two series of experiments were carried out. In the first series, two types of structures, which are I-shape and U-shape structures have been studied in a horizontal channel. In the second series of experiments, riverbed slopes of 1%, 2.5% and 5% were tested. For each type of structure, three heights in different hydraulic conditions including densimetric Froude numbers and drop heights were tested. Results show, that the ratio between the length of the structure and the channel width is one of the most important nondimensional parameter to classify the scour. New analytical functions have been derived from dimensional analysis to predict the maximum scour depth, the maximum length of the scour, location of the maximum scour depth and the maximum development of the scour width. All the experiments were conducted in clear water conditions. Based on dimensional analysis and using all collected data new equations have been obtained. Scour morphology downstream of Cross-Vane structure was classified in different scour patterns based on different flow hydraulic conditions, structures geometries and the ratio between the maximum length of the scour and the channel width.

Scour characteristics downstream of rock W-weir structures were studied in a horizontal straight channel and under clear water conditions. For each structure, different hydraulic conditions were considered, including densimetric Froude numbers, water drops, and tailwaters. Results showed that the tailwater depth plays an important role in predicting the scour parameters. Dimensional analysis was used to derive equations to predict the maximum scour depth and length and the maximum dune height and length. Selected tests were conducted with an open W-weir. In this case, results show that the maximum scour depth decreases and its location shifts downstream with respect to classical W-weirs. Three types of scour morphology were classified: Type A, characterized by one scour hole and two ridges; Type B, with two scour holes and two ridges; and Type C, characterized by only one scour hole and one ridge.

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.