Sediment Continuity Research Articles

Stationary and pulsed electrodeposition of silicon in LiCl–KCl–CsCl–K2SiF6 melt

Silicon and its materials are widely used in metallurgy, micro- and nano-electronics, solar energy, and are also promising materials for anodes of lithium-ion power sources with increased specific capacity. The expansion of application areas of silicon with controlled morphology necessitates the development of new energy–efficient methods of its production. In the present work, the influence of the mode as well as parameters of electrolysis of the LiCl–KCl–CsCl–K2SiF6 melt with a temperature of 545 оC on the morphology of electrolytic precipitation of silicon on glassy carbon has been studied. The galvanostatic mode of electrodeposition, widely used in industry, as well as the pulsed mode, which is actively investigated at present, were used for the electrolysis. Silicon electrodeposition was carried out by varying such parameters as cathodic current density (from 3 to 50 mA/cm2) and electrolysis duration (from 30 to 180 min) in the galvanostatic mode, as well as by varying the density and duration of the cathodic current pulse, the duration of current pauses and the total duration of electrolysis in the pulsed mode. It is shown that electrodeposition of silicon on glassy carbon is accompanied by the formation of a continuous sediments of hemispherical nuclei with a diameter of about 1 micron on the electrode surface. An increase in the cathodic current density and an increase in the cathodic current pulse pause frequency contribute to the disruption of the sediment continuity and the growth of dendrites of ordered or arbitrary shape. At the same time, the pulsed mode allows to increase the cathode current density at silicon electrodeposition (from 25–30 to 250–500 mA/cm2) and stabilize the value of the cathode potential during electrolysis.

Assessing the effect of torrent control structures on sediment continuity and connectivity

The study investigated the effect of torrent control structures on the sediment cascade in the Vegliato mountain basin (Italy) related to an intense rainfall event of 50 years return interval. The Index of Connectivity (IC) was exploited to analyze the interaction of structures with longitudinal sediment (dis)connectivity. Moreover, the Sediment Continuity Ratio (SCR) was used to assess the effect on sediment (dis)continuity. The SCR is a novel parameter considering for each torrent control structure, the net balance of sediment deposition and erosion, and the cumulative proportion of the sediment cascade arriving from upstream. The SCR emphasises which structure was more prone to continuity or discontinuity during an event and to what extent compared toother structures. Moreover, a multi-perspective framework was carried out to help the interpretation of the SCR results within the context of the study area. The results of the (dis)connectivity assessment showed that the torrent control structures impacted sediment dynamics by influencing the slope and flow confinement, which in turn affected the IC. The (dis)continuity assessment showed structures prone to continuity mainly located in the upstream part of the catchment, where most of the over 60000 m3of sediment was generated. In contrast, structures prone to discontinuity were located in the downstream part, where deposition processes were favoured during the analyzed period. A total of 65 % of the structures similarly affected both (dis)continuity and(dis)connectivity. Data on individual structure functions and maintenance conditions were also included, emphasizing the importance of these factors in planning mountain basins management interventions.The study proposed a new metric that, despite being based on a single large event and a single basin, still provides a useful approach to investigate the interaction between sediments and individual structures, the entire sediment cascade and the channel control system.

Modeling the morphological response of gravel–bed rivers subject to repeated sediment bypass tunnel operations

Introduction: Sediment bypass tunnels (SBTs) are operated during floods to re-establish sediment continuity past dams with the ultimate goal of decreasing accumulation in reservoirs. Depending on the location of the intake structure and operational conditions, SBTs may release either bed load-laden or bed load-free flows in the form of sudden floods (pulses). When evaluating the impacts of SBTs, the traditional approach has been to monitor channel changes in the years following project completion. However, by the time these impacts become evident, mitigation is challenging.Methods: This research adopts a forward-thinking methodology, emphasizing the prediction of potential impacts during the project’s early planning stages. We use a one-dimensional morphodynamic model to forecast the potential morphological response of a gravel-bed river with an idealized geometry to a series of SBT operations characteristic of projects in the Swiss Alps.Results: The morphological response of the downstream reach over the medium to long term is influenced by the alternating pattern of bed load-laden and bed load-free flow releases. This pattern is instrumental in forming a transition region near the SBT outlet hydrograph boundary layer (HBL).Discussion: Within the (HBL), fluctuations in bed elevation and slope are localized, while variations in grain-size distribution persist throughout the downstream region.

Quantification of bedrock structural controls of longitudinal sediment connectivity using the probability of connectivity and sediment continuity model

The structural controls of sediment connectivity are poorly understood in low-gradient watersheds and stream networks. We developed a field- and modeling-based framework to understand the timescales and thresholds associated with the structural controls of sediment connectivity and continuity in the Inner Bluegrass region of Kentucky, USA. Field reconnaissance was carried out to assess stream morphology and sediment connectivity, which was leveraged to derive instream sediment connectivity indices for 181 pool-riffle sequences in the low-gradient bedrock stream network. Our model framework coupled a probability-based connectivity formulation with the sediment continuity formula to assess sediment transport and connectivity in the stream network. Results indicated that the bedrock system reflects an end-member in which lithology controls longitudinal stream morphology. Specifically, we found that regional morphology controls pool-riffle length scales via bedrock outcrops, which therein controls the timescales of sediment connectivity over multiple hydrologic regimes. The pool to riffle length ratio was found to be 4.6, an order of magnitude greater than the ratio for alluvial systems. The new formulation of the sediment continuity formula coupled with the probability of connectivity framework adequately captured both short-term and long-term continuous dynamics of sediment transport, as indicated by evaluation metrics with measured sediment flux and field reconnaissance. Based on the analysis of 362 riffles and pools, we found that sediment in pools upstream of bedrock outcrop barriers are disconnected 93 % of the time whereas riffles are connected and allow full continuity 99 % of the time. Longitudinal sediment connectivity within the stream network was found to be controlled by both functional connectivity and structural connectivity, which contrasts recent findings describing the controls of sediment connectivity over lateral pathways on hillslopes.

Early assessment of effects of dam removal on abiotic fluxes of the Selune River, France

The Water Framework Directive set for European Union countries the objective of restoring the ecological and/or sediment continuity of rivers, as the latter is relevant for providing suitable habitats for the former. Indeed, abiotic fluxes and variables shape riverine ecological habitats and are likely to be modified by barriers such as dams. Two dams were removed from the Selune River (northwestern France) from spring 2017 to summer 2022. The objective of this study was to describe and quantify how the dams modified abiotic parameters and fluxes, as well as the dynamics of these fluxes during dam removal. We monitored coarse and fine sediments, water temperature and nutrient concentrations in the Selune River from upstream to downstream of the dams from 2015 to 2023. The results showed that coarse sediments of the riverbed are a legacy and that current hydrodynamic conditions are not sufficient to move them much, with or without the dams. In addition, it appears that at this early stage after the removal some downstream parameters, especially nutrient concentrations and water temperature, have already converged towards upstream signals, while fine sediment stored in the dam’s reservoirs are still destocking. Restoring ecological continuity of the Selune River will involve dynamics of abiotic parameters over longer time scales, in response to removal of the dams, and over larger spatial scales, in response to climate and other global changes.

Flushing Efficiency of Run-of-River Hydropower Plants: Novel Approaches Based on Physical Laboratory Experiments

Periodic flushing operations during moderate flood events (≤annual flood flow HQ1) are an approach to counteract problems caused by disturbed sediment continuity in rivers, which is possibly an effect of run-of-river hydropower plants (RoR-HPPs). Considering ecology, flood risk, technical, and economical reasons, discharge values of 0.7 × HQ1 are a good reference point for the initiation of gate operations. This work aimed to investigate the role of different gate opening actions on the effectiveness of such flushing measures. Physical model tests were performed, to capture bed load rates, together with 2D velocity measurements in the vicinity of two movable radial gates above a fixed weir. The length scale of the idealized model arrangement was 1:20, and a conveyor-belt sediment feeder was used to supply a heterogeneous sediment mixture. Velocities were acquired using 2D laser doppler velocimetry (LDV). Based on the LDV measurements, mean velocity profiles and Reynolds stresses were derived. The full opening of both radial gates led to the highest bed load mobility. While the flushing efficiency drastically decreased, even for slightly submerged gates, an asymmetrical gate opening initially led to the formation of a flushing cone in the vicinity of the weir, accompanied by temporarily high flushing efficiency. In conclusion, our results stress the importance of full drawdowns in successfully routing incoming bed load downstream of the HPP. However, the combination of an asymmetric gate opening followed by a full drawdown could be a promising approach to further improve the flushing efficiency of RoR-HPPs.

Combined usage of geophysical methods in continental water bodies, their benefits and challenging issues: A special focus on sediment deposits in dam reservoirs

Hydraulic structures such as dams have a direct or indirect influence on the hydro-sedimentary functioning of rivers. They can impact the sediment continuity of the river and can create a sediment imbalance with zones of sediment accumulation upstream and a lack of sediment downstream from the dam. Sediment deposits upstream dams are a major issue for managers as they can impact the operation and/or affect the safety of the structure and increase the flood risk. Operators therefore seek to determine the physical characteristics of these deposits to determine their remobilization potential. Usually, these sediment deposits are described using bathymetric data, sonar images or sedimentary information (dredging, coring). For this study, new measurements from two geophysical methods (acoustic and electromagnetic) were used in addition to these current monitoring methods. In addition, this method can be essential when historical data is not available. The contribution of geophysical techniques is undeniable to improve the characterization of these deposits. These measurements make it possible to: i) define the internal structures of the sediments, ii) determine the spatial distribution of these structures over the entire development, iii) evaluate the volumes deposited when little bathymetric data is available on the reservoir. The coupling of these methods thus makes it possible to reconstruct the evolution and the structuring events of the sedimentary deposits. This approach provides complementary and important information for stakeholders in terms of dam exploitation and management of sedimentary deposits.

Effect of sediment transport, flow depth and infiltration on soil moisture profiles in irrigation furrows

A numerical model was used to analyze the effect of sediment transport and flow depth on soil moisture profiles from a simulation of the hypothetical irrigation furrows. The Saint Venant and sediment continuity equations were solved by using MacCormack scheme based on finite difference method to analyze the overland flow and sediment transport, and Richards equation was used to analyze the subsurface flow, which was solved by using a mass conservative fully implicit finite difference method. Flow depth significantly affected the moisture profiles in irrigation channels while the effect of sediment-laden water on the moisture profiles was observed insignificant. The model was used to study the effect of infiltration on moisture profiles and soil water retention curve (SWRCs) in irrigation furrows. It was observed that infiltration significantly affected and altered the moisture profiles and soil water retention curve (SWRC). Among the different soil parameters (av and nv ) and saturated hydraulic conductivity () significantly affected the moisture profiles, while and influenced the soil water retention curve (SWRC) as compared to other retention parameters.

Numerical model of local scour considering the unsteady sediment inflow and sediment sorting: Application to scour upstream of slit weir

The current study proposes a novel framework for the numerical model for estimating the temporal scour considering unsteady sediment inflow and the sediment sorting process. The framework was applied to local scour upstream of a slit weir. The scour model is based on an ordinary nonlinear differential equation derived from sediment continuity and scour rate equations. A one-dimensional (1-D) Boussinesq-type model coupled with nonequilibrium sediment transport was incorporated in the scour model to consider unsteady sediment inflow. In addition, a mixing layer approach was incorporated to determine temporal variations in particle size in the scour hole. The proposed framework was validated using scour experiments conducted under conditions that include non-uniform sediment, live-bed scour, and unsteady flow rate. The simulation results showed satisfactory agreement with experimental results for the scour upstream of a slit weir. The proposed model appropriately explained the hysteresis process for flow unsteadiness, refilling process for live-bed scour, and armoring process for non-uniform sediments. In addition, the model framework proposed in the current study is applicable to local scour around other hydraulic structures (e.g., bridge piers) upon establishing the scour rate equation. Therefore, the current study provides a novel approach for modeling temporal scour that is required to consider unsteady sediment inflow and sediment sorting.

Basin‐wide hydromorphological analysis of ephemeral streams using machine learning algorithms‡

AbstractSustainable river management now encompasses a much wider concept that includes hydromorphological and fluvial habitat studies. In ephemeral streams, the geomorphological characterization of channels is complex due to episodic flows and riparian vegetation dynamics. Stream channel survey and classification at the watershed scale provide the basis for geomorphological conservation, process interpretation, assessing sensitivity to disturbance, and identifying reaches that supply and store sediment. Here, we present a stream classification based on a two‐step approach: (1) automatic river segmentation based on spatial variability in channel/valley morphology from topographic measurements (LiDAR, light, detection and ranging), and (2) fluvial landform and vegetation density mapping derived from multispectral open‐source satellite images (Sentinel‐2) using support vector machine (SVM) and Random Forest (RF) algorithms. These analyses provide continuous, quantitative spatial values of geometric (channel/valley width, slope gradient, and route distance), landform (active channel and gravel bars with five densities of vegetation cover), and hydraulic (specific stream power) variables. Four stream types were identified in the Rambla de la Viuda catchment (~1500 km2), an ephemeral gravel‐bed river in eastern Spain. The spatial distribution of channel types is explained by differences in geometry (active channel width, valley width, and slope gradient) and a hydraulic parameter (specific stream power). The landforms/vegetation patterns provided insight on causal relationships between erosion and deposition processes during high flow periods and the time since the most recent large disruptive flood event. Channel type distribution provided first‐order predictions about the location of reaches that supply and store sediment and thus information on sediment continuity along the river. Dam effects on downstream reaches resulted in geomorphological disequilibrium, producing narrowing of the active channel, slope reduction, and a decrease of gravel bar areal extension. The proposed catchment scale analysis provides a comprehensive and replicable methodology for environmental planning in Mediterranean ephemeral streams to guide further hydromorphological surveys at the reach scale.

ANALISIS ABRASI DAN AKRESI PERAIRAN PANTAI BARUS TAPANULI TENGAH DENGAN MODEL CEDAS 2.0

Barus is an area where most of the people are fishermen, this is because Barus is an area located on the coast. The existing condition shows the shoreline on the east side of the seawall building, the condition of the shoreline is experiencing abrasion resulting in the retreat of the coastline and almost reaches the fisherman's flat building area, this is due to the port building in the form of a massive trester jutting into the sea resulting in sediment supply to the retained flat towers and the coastline has declined.To maintain the stability of the coastline, it is necessary to make an effort to control the damage to water in this area. The shoreline model is a numerical forecast model based on the sediment continuity equation and the sediment transport rate equation along the coast. Sediment transport rates along the coast are a function of the variation in height and direction of waves along the coast formed by the effects of refraction and diffraction.
 The results of the shoreline change model with the protection of the fisherman's flat area from waves by building sea walls is the east side of the fisherman's towers abrasion ± 7 m and sedimentation ± 5 m, the front area of the fisherman's towers does not occur sedimentation or abrasion, the western side of the fisherman's towers does not sedimentation and abrasion occurred, the east side of Barus Jetty did not occur abrasion or sedimentation, the area of Barus Jetty occurred ± 20 m sedimentation, and the west side of Barus Jetty occurred sedimentation ± 9 m. These results indicate that for handling conditions by making a seawall in front of the flat area shows that the location is safe from scouring of waves

Hydrodynamics and sediment transport under a dam-break-driven swash: An experimental study

An experimental study is presented consisting of swash zone hydrodynamics, sediment transport flux estimates, and bed changes under a single dam-break-driven swash event over a steep (1:7), movable sand bed. The study provides resolved measurements of instantaneous water depths, cross-shore flow velocities, sheet flow and suspended sediment concentrations, and morphological response. An ensemble-averaging over 24 repetitions of the swash event allows convergence in the time-averaged measured swash quantities. The sand bed profile was re-constructed after each run with a re-smoothing procedure that allowed for minimum variations that are within the profiler system accuracy (<0.006 m). High-resolution measurements are employed to reconstruct the spatial-temporal evolution of the flow velocity field. Temporal extrapolation and spatial logarithmic/exponential fits are employed to fill velocity gaps in the measured data for the estimation of instantaneous and depth-integrated sediment flux. The spatial gradients of instantaneous sediment flux indicate that the sheet flow sediment dominates over the suspended load during the most relevant phases for sediment transport. Upon bore arrival and initial uprush, the relative contribution of the sheet flow load is larger than during the backwash phase and is decreasingly dominant onshore. Depth-integrated instantaneous sediment flux and total sediment transport estimates, based on two different approaches, are compared with equivalent total sediment transport estimates obtained from the observed morphological changes and the sediment continuity equation. The close agreement between the various approaches indicates that existing models and empirical estimates for the sheet load concentration profile can be used as first order estimates for sediment transport in the swash zone.

Morpho-sedimentary dynamics associated to dam removal. The Pierre Glissotte dam (central France)

The paper emphasizes the main lessons learned from hydromorphological monitoring following the removal of a medium-sized dam (7.29 m) located on a medium energy gravel bed river over a four year period (2015–2019). The Pierre Glissotte dam was previously located on the upper Yonne river (Morvan massif), where it was an obstacle to sediment continuity and was almost completely filled with sand and silts. The dam was removed in two steps, the first in July 2015 and the second in October 2017. Several methods were used (topographical surveys, SFM photogrammetry, RFID tracking, hydrological monitoring) to characterize river adjustments, i.e. the nature of the morpho-sedimentary dynamics, their rates, their temporal and spatial variations, and their control mechanisms. The results highlight the complex and nonlinear response of the Yonne river and the relevance of a regular prolonged monitoring. The changing patterns in space and over time, underline the vast range of uncertainties surrounding this type of restoration and the difficulty involved in predicting post-removal hydromorphology around the dam (return to pre-dam functioning, no changes, new equilibrium conditions). For instance, up to now, the study shows that intense morpho-sedimentary dynamics in the reservoir and effective restoration of bedload continuity do not necessarily lead to changes in the downstream conditions (bed mobility and morphological configuration) previously shaped under the influence of the dam, thus mitigating the success of the river restoration operation.

Impact Force of a Geomorphic Dam-Break Wave against an Obstacle: Effects of Sediment Inertia

The evaluation of the impact force on structures due to a flood wave is of utmost importance for estimating physical damage and designing adequate countermeasures. The present study investigates, using 2D shallow-water approximation, the morphodynamics and forces caused by a dam-break wave against a rigid obstacle in the presence of an erodible bed. A widely used coupled equilibrium model, based on the two-dimensional Saint–Venant hydrodynamic equations combined with the sediment continuity Exner equation (SVEM), is compared with a more complex two-phase model (TPM). Considering an experimental set-up presented in the literature with a single rigid obstacle in a channel, two series of tests were performed, assuming sand or light sediments on the bottom. The former test is representative of a typical laboratory experiment, and the latter may be scaled up to a field case. For each test, two different particle diameters were considered. Independently from the particle size, it was found that in the sand tests, SVEM performs similarly to TPM. In the case of light sediment, larger differences are observed, and the SVEM predicts a higher force of about 26% for both considered diameters. The analysis of the flow fields and the morphodynamics shows these differences can be essentially ascribed to the role of inertia of the solid particles.

Discontinuous Galerkin methods for a dispersive wave hydro-morphodynamic model with bed-load transport

A dispersive wave hydro-morphodynamic model coupling the Green–Naghdi equations (the hydrodynamic part) with the sediment continuity Exner equation (the morphodynamic part) is presented. Numerical solution algorithms based on discontinuous Galerkin finite element discretizations of the model are proposed. The algorithms include both coupled and decoupled approaches for solving the hydrodynamic and morphodynamic parts simultaneously and separately from each other, respectively. The Strang operator splitting technique is employed to treat the dispersive terms separately, and it provides the ability to ignore the dispersive terms in specified regions, such as surf zones. Algorithms that can handle wetting–drying and detect wave breaking are presented. The numerical solution algorithms are validated with numerical experiments to demonstrate the ability of the algorithms to accurately resolve hydrodynamics of solitary and regular waves, and morphodynamic changes induced by such waves. The results indicate that the model has the potential to be used in studies of coastal morphodynamics driven by dispersive water waves, given that the hydrodynamic part resolves the water motion and dispersive wave effects with sufficient accuracy up to swash zones, and the morphodynamic model can capture the major features of bed erosion and deposition.

Numerical and experimental investigations on aggradation and degradation in irrigation canals accounting for infiltration*

AbstractA numerical model was used in the present study to predict aggradation, degradation, and subsurface moisture content in irrigation canals. The numerical model solved Saint‐Venant and sediment continuity equations to analyse overland flow and sediment transport, whereas Richard's equation was used to analyse subsurface movement of water. Saint‐Venant and sediment continuity equations were solved by using the MacCormack scheme based on the finite difference method, and the Richard's equation was solved by using a mass‐conservative fully implicit finite difference method. Extensive irrigation canal experiments involving measurement of aggradation, degradation, and subsurface moisture content were conducted to assess the performance of the numerical model. The predicted aggradation and degradation represented a good agreement with data recorded in laboratory. Soil moisture profiles were estimated for sediment‐laden water and clear water conditions in irrigation canals. But the effect of sediment‐laden water on the moisture profiles was observed as insignificant. The observed and the model‐predicted soil moisture varied marginally as the observed moisture was attributed to errors during the collection of soil samples from the experimental field.

A Numerical Model for 1D Bed Morphology Calculations

The present work proposes a new morphodynamic model for flow simulation in open channels. The governing one dimensional (1D) shallow water equations along with the Exner sediment continuity equation are solved here using coupled approach. A TVD based MacCormack predictor corrector method is used here for solution of the coupled governing equations. The developed numerical model is used to replicate several test cases of known experimental and approximate solutions. These cases include bed aggradation due to sediment overloading, bed degradation due to sediment shut-off, dam break flow over erodible bed and movable bump due to subcritical and transcritical flows. The results obtained are found to be excellent and free from oscillations near sharp gradient. The numerical model is also found to be capable of capturing the wave-fronts of both water surface and bed sediment. Quantitative analysis of the results in terms of two statistical parameters establishes the potential of the present model in more complicated practical problems.

Best groyne series as countermeasure against river bend scour

A new approach for finding a cost-effective combination of groynes in a channel bend for the prevention of bend scour is presented. A linked simulation–optimisation model is proposed for this purpose. The morphological flow simulation model was developed by solving the shallow-water equations and the Exner sediment continuity equation in a boundary-fitted coordinate system. The optimisation model was developed utilising a binary-coded genetic algorithm. The proposed model can automatically provide a cost-effective groyne series in terms of their number, length and position in any vulnerable channel bend. A constraint in terms of bend scour is also incorporated in the optimisation model, which allows the optimisation model to obtain the best groyne combination for no bend scour. To appraise the performance of the model, it was applied to a hypothetical vulnerable channel bend. The model produced the minimised cost of installation of the groyne system at that location, at the same time as making the location free from bend scour.

Process‐based assessment of success and failure in a constructed riffle‐pool river restoration project

AbstractAlthough there is increasing consensus that river restoration should focus on restoring processes rather than form, proven techniques to design and monitor projects for sediment transport processes are lacking. This study monitors bedload transport and channel morphology in a rural, an urban unrestored, and an urban restored reach. Objectives are to compare bedload transport regimes, assess the stability and self‐maintenance of constructed riffle‐pool sequences, and evaluate the impact of the project on coarse sediment continuity in the creek. Sediment tracking is done using radio frequency identification tracers and morphologic change is assessed from repeated cross‐section surveys. Mean annual velocity is used to quantify the average downstream velocity of tracers, defined as the mean overall tracer travel length divided by the total study duration. The channel reconstruction slows down the downstream velocity of particles in the D75 and D90 size classes, but does not significantly change the velocity of particles in the D50 size class or smaller. Surveys show that riffle features remain stable and that pool depths are maintained or deepened, while tracer paths match with what has been observed in natural riffle‐pools. However, the slowdown of coarse sediment and increase in channel slope may lead to future failures related to over‐steepening of the banks and a disruption in the continuity of sediment transport in the creek. This study demonstrates how bedload tracking and morphological surveys can be used to assess river restoration projects, and highlights the importance of incorporating coarse sediment connectivity into restoration design and monitoring.

Can coarse bedload pass through weirs?

Restoring active bedload transfer in human-impacted rivers has received increasing attention in recent years, notably in response to the European Water Framework Directive (WFD), which requires that the continuity of rivers not be disturbed by anthropogenic features such as dams or weirs. The Bocq River (233 km2), a moderate-gradient stream in Wallonia, Belgium, has a hydraulic resource that was formerly largely exploited with 74 weirs (up to 2.3 m high) along 43 km. We examined the effects of seven old abandoned weirs on bedload transport for three different types of weirs (defined by the presence and position of the sluice gate system). First, the volume estimates of bedload stored in reservoirs indicated that, despite their old age, the reservoirs were not completely filled (between 25 and 50% filled compared to the reservoir volume capacity) and did not evolve very much since 1990. Second, the grain size analysis of bed material upstream, downstream and within the reservoirs, and the direct measurements of sediment transport (slag particles and PIT-tagged pebbles) demonstrated that bedload continues to be transported out of the reservoir, even though the selective trapping of coarser elements was observed within the reservoir. Particles in the range of the median can pass over the crest of weirs, but the coarser elements tend to remain in the reservoirs. This trapping effect is mitigated when the weir has open or collapsed flushing gates that facilitate bedload transfer. This indicates that weirs act as leaky barriers that allow bedload to pass through, although the individual geomorphic setting plays a primary role in determining the local sediment continuity. These findings suggest that river connectivity is less impacted than initially thought and is likely to increase over time as old weirs gradually fall into disrepair. This needs to be acknowledged when planning barrier removal projects.