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A study on the time development of local scour around a complex pier was developed using a small-scale model embedded in a sediment bed. A total of 15 laboratorial tests were performed at the Hydraulics Laboratory of the Faculty of Engineering of the University of Porto. The duration of each experiment was previously established to progressively characterize the scour cavity. After each experiment, the flume was gradually emptied to facilitate the application of closerange photogrammetry. The scour depth values resulting from the application of photogrammetry at the pile cap front agree well with the values obtained experimentally. The temporal development of the scour cavity is presented and discussed. Empirical formulas for the scour cavity time development and for the relation of scour depths to scour cavity volumes were obtained. The obtained threedimensional models can also be used for calibration and validation of numerical models.

The prediction of scour evolution at bridge foundations is of utmost importance for engineering design and infrastructures’ safety. The complexity of the scouring inherent flow field is the result of separation and generation of multiple vortices and further magnified due to the dynamic interaction between the flow and the movable bed throughout the development of a scour hole. In experimental environments, the current approaches for scour characterization rely mainly on measurements of the evolution of movable beds rather than on flow field characterization. This paper investigates the turbulent flow field around oblong bridge pier models in a well-controlled laboratory environment, for understanding the mechanisms of flow responsible for current-induced scour. This study was based on an experimental campaign planned for velocity measurements of the flow around oblong bridge pier models, of different widths, carried out in a large-scale tilting flume. Measurements of stream-wise, cross-wise and vertical velocity distributions, as well as of the Reynolds shear stresses, were performed at both the flat and eroded bed stages of scouring development with a high-resolution acoustic velocimeter. The time-averaged values of velocity and shear stress are larger in the presence of a developed scour hole than in the corresponding flat bed configuration.

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The complex flow structure around bridge piers is challenging for both experimental and numerical studies. Therefore, investigating the capabilities of Computational Fluid Dynamics (CFD) tools in resolving the flow structure and the mechanism of sediment entrainment into and out of the scour hole remains a challenging task. In this study, the scour depth around an oblong bridge pier and the bed shear stress distributions in time and space were numerically investigated using the Computational Fluid Dynamics (CFD) tool Sediment Simulation In Intakes with Multiblock option (SSIIM). Clear water scour conditions and sand of known granulometric composition were considered in accordance with the experimental study carried out. Laboratory data and the results of a scour characterization around a 0.11 m wide oblong bridge pier were considered to calibrate and validate the numerical model. The averaged form of the Navier–Stokes equations was considered to simulate the turbulent flow fields in anticipation of long time scales. The results show that calibrated numerical models can reproduce measured scour depths in the laboratory environment with considerable accuracy, with an average relative error of less than 3%, especially around oblong bridge piers.

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The present work aims to provide reliable estimates of extreme discharge flows and their probability of occurrence. Such estimates are important for the assessment of the associated hydrological risk of hydraulic infrastructures, such as bridges and dams, in the design process as well as during their operations. The hydrological modeling herein developed was applied to estimate the design floods approaching the new Hintze Ribeiro bridge, in the north of Portugal. It proposes a statistical analysis of the maximum annual streamflow data by using a flood frequency analysis technique. The data series were subject to a reliability analysis and the specific modeling assumptions, required for the study, were appropriately given and tested. An extrapolation technique of the missing instantaneous discharge data was herein derived. Such technique was validated by two distinct methods. The estimations are accurate with a mean deviation of 7.2% relative to the observed data. A set of probabilistic models were considered and the models' performance verified by the goodness-of-fit tests and Q-Q plots. The model and the parameter uncertainties were taken into account. Model uncertainties were addressed by comparing the estimated design floods through selecting the best fitting probability model (MS) with the approach that considered the distribution functions which fit well the data (MM). On the other hand, the computed flow rates were estimated with 95% of confidence to reduce the inherent parameter uncertainties. An additional accuracy assessment of the parametric approaches was performed through a comparative analysis of such design floods with the ones retrieved by application of the non-parametric Kernel density estimate (KDE). The MM approach showed a lower discrepancy (18.5%) to KDE estimates, when compared with the MS results. A sensitivity analysis of the associated hydrological risks was also undertaken.