Journal of Hydraulic Engineering

Understanding the flood impact dynamics on buildings is still a major challenge, especially considering the built environment. Motivated by the problem of the flood-structure interaction, this study experimentally measured loading conditions onto three-dimensional buildings to investigate flood loading mechanisms considering the shadowing effect. A total of 162 scenarios concerning different values of the initial impoundment depth ($H_i$), aspect ratio of the front building ($\alpha$), relative longitudinal spacing ($\lambda$), and orientation of the front building ($\theta$) were undertaken. Both flood loading mechanisms with and without considering the shadowing effect were discussed elaborately. Results showed that the existence of the front building leads to a dramatic change in flow regime upstream of the rear building, and the shadowing effect highly depends on the development of the flood flow reconstruction. In addition, the shadowing index ${\eta }_F$ was introduced, and it was more sensitive to $\lambda$ than $\alpha$ and $\theta$. When the $\lambda$ was less than 3.5, relative optimal values of $\theta$ were 50°, 45°, and 0° for the scenarios with $\alpha =0.5$, $\alpha =1.0$, and $\alpha =1.5$, respectively. There was a negative dependence of the flood hazard level on the shadowing index. Besides, the modified formula of the maximum flood impact force considering the shadowing effect and fitting formulas between $\lambda$ and $k_s$ were obtained. This research supports the study of flood loading mechanisms and is beneficial to the plan and design of safer building clusters.

The complex process of sediment infiltration in gravel beds has been studied widely. However, the temporal behavior of sediment infiltration and its clogging has not yet been investigated sufficiently. To understand the mechanisms involved in this phenomenon, measurements of the effects of various boundary conditions are required with high spatial and temporal resolution. The nonintrusive and undisturbed gamma-ray attenuation method was applied in this study to establish a measuring scheme to detect the dynamic development of river bed clogging and to investigate the effects of fine sediments’ particle-size distributions, total supplied mass, and supply rate on the sediment infiltration process. In a series of experiments, vertical profiles of infiltrated sediment masses were measured at two instants during the experiments. Then the dynamic changes of the infiltrated sediments at a specific position of the bed were investigated using continuous measurements during the experiments. The results of the measured vertical profile showed that sediment infiltration and clogging in an artificial bed matched the sediment’s existing bridging criterion of the porous gravel bed. Furthermore, temporal changes occurred mainly in the upper layers. The continuous one-point measurements indicated almost real-time sediment accumulation development and proved that higher supply rates lead to an earlier start of the infiltration and rapid filling, whereas lower supply rates result in later and slower infiltration of the sediments.

Engineering modifications of rivers, e.g., dams or groynes, often induce long-term riverbed erosion, which can be mitigated with sediment nourishments. Here, we consider nourishments to mitigate channel bed erosion induced by channel narrowing, as opposed to the more common application downstream of dams. Our objective is to assess and quantify how dumping location, grainsize, and volume are important for mitigation efficacy. Our results show that erosion can be mitigated if nourishments change the sediment flux such that the corresponding equilibrium channel slope is increased. This is achieved by coarsening the sediment flux throughout the reach, increasing magnitude of the sediment flux, or both. Flux is coarsened via additions of sediment at or coarser than the bed surface and nourished sediment should be distributed throughout the incising reach. The second option is nourishing a large volume of relatively fine sediment to increase the equilibrium channel slope. Additions of fine sediment in small volumes decrease the equilibrium channel slope and enhance erosion, because the fine sediment flux makes the gravel more mobile.

The study of local scour in bridge foundations is often restricted to quantifying maximum scour depth on the upstream side. This is limiting to the understanding of the resulting scour by numerical methods, for which the shape of the scour hole is a mandatory input. In this work, two nonintrusive three-dimensional (3D) image-based measuring techniques, consisting of close-range photogrammetry and a Kinect V2 sensor, were employed to characterize the initial and final development of scour holes around piers, under steady flow in a laboratory flume. A novel two-dimensional (2D) methodology was also applied for continuous measurement of the side of the scour hole using submersible cameras. Models of the scour hole geometries in the vicinity of two oblong bridge piers were obtained at high accuracy levels. A database for calibration and validation of numerical models is thus provided.

The stability of lining slabs in stilling basins is crucial for ensuring safety during flood discharge from large dams. Accordingly, this paper compares the stability of pervious slabs featuring keyways to impervious slabs without and with keyways. The experimental results demonstrate that the maximum uplift force exerted on pervious slabs with keyways and its standard deviation was less than that exerted on the other two types of slabs because the fluctuating pressure beneath the pervious slabs with keyways was considerably lower than that beneath the traditional slabs. The keyways strengthened the interaction between the slabs and lengthened the propagation route of the pressure fluctuations. The pressure fluctuations acting on the upper face and beneath the lower face of the pervious slabs tended to be in phase due to the propagation of the fluctuating pressure through the holes. The proposed pervious slabs with keyways could considerably increase the stability of the lining slabs in stilling basins.