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Fine sediment infiltration and subsequent clogging in a gravel bed affect several fluvial, ecological, and biological processes, resulting in the degradation of the river ecosystem. Despite many experimental and a few numerical studies, the process is yet to be entirely understood. We employed a pure Lagrangian framework, called the Discrete Element Method (DEM), to numerically investigate the infiltration process. Special attention is given to tackling the issue of non-spherical and irregular particle shapes and particle size distributions (PSDs) in numerical simulations. Due to computational limitations, these aspects were either not considered or simplified in previous numerical studies. We implicitly included non-spherical and irregular shape effects through rolling resistance models, which do not cause excessive computational overhead. Our study shows that rolling resistance models greatly influence packing and fine sediment infiltration. However, they may also lead to unphysical particle behavior; thus, they should be carefully used in numerical simulations. Oversimplified PSDs do not mirror natural systems, and full PSDs pose computational challenges. Sufficient grain classes are needed to mimic the non-homogeneity and poly-dispersity found in natural fluvial sediments. The infiltrating characteristics of sand concerning PSD and shape effects are linked to size ratio D15,Gravel/D85,Sand, assuring physical and realistic modeling of the infiltration process. [ABSTRACT FROM AUTHOR]

Culvert blockage is a recognized problem known to increase the risk of cross-drainage failure. Presently, the effects of bottom-up inlet blockage can be estimated using the theoretically derived energy loss method (ELM) and reduced area method (RAM). Both methods imply that hydraulically efficient inlets are more resilient to blockage effects but have not been verified experimentally for bottom-up blockages. In this study, a physical culvert model was used to determine the entrance loss coefficients and head-discharge relationships for commonly used pipe culvert inlets under different combinations of bottom-up blockage ratio, shape, and roughness. The experimental results confirm that hydraulically efficient inlets are more resilient to bottom-up blockage. Under submerged outlet control conditions, it was found that both blockage ratio and shape significantly influence the entrance loss coefficient and that ELM overestimated the entrance loss coefficient by up to 124%. Under inlet control conditions, it was found that only the blockage ratio significantly influenced the head-discharge relationship and that RAM underestimated the blockage discharge ratio by up to 38%. Comparisons to the experimental results show that ELM and RAM do not account for the increased efficiency of the unblocked part of the inlet under conditions of bottom-up blockage. Comparison to embedded inlets shows that they result in significantly lower entrance loss coefficients than partially blocked inlets under outlet control but yield similar discharge capacity ratios under inlet control. Uncertainties and estimation errors are given for the results, and validity for use in minimum performance design frameworks is evaluated for the different flow types used in hydraulic culvert design. The results show the importance of evaluating blockage effects as part of hydraulic culvert design and verify the general predictions of the energy loss method and reduced area method; that hydraulically efficient inlets are more resilient against blockage effects. The results are valid for type 1 and 5 (inlet control) and 4, 6, and 7 (outlet control) flows and can be used with existing design methods in the following ways: (1) informing the choice of inlet design, for both unblocked and blocked conditions; (2) including a blockage ratio in the design of culverts, based on registered blockage data or risk assessments; (3) evaluating necessary maintenance regimes based on acceptable blockage ratios; and (4) evaluating the effects of blockage on stream continuity. Given the large variation in in situ inlet blockage conditions, it is recommended to use the maximum values of entrance loss coefficients (keb) and the minimum discharge ratio (Qb/Q) as a conservative approach for bottom-up blockage effects. Recommended design blockage ratios given in design manuals should be supplemented with registered data on blockage history for specific locations. For data registration and monitoring, the blockage ratio (Ab/A) should be recorded. [ABSTRACT FROM AUTHOR]

Mismanaged plastic waste threatens the sustainable development goals of the United Nations in social, economic, and ecological dimensions. In the pollution process, fluvial systems are critical transport paths for mismanaged plastic waste, connecting land areas with oceans and acting as plastic reservoirs and accumulation zones. The complex fluid–plastic particle interaction leads to a strong distribution of transported particles over the entire river width and flow depth. Therefore, a holistic plastic removal approach must consider lateral and vertical river dimensions. This study investigates the conceptual design of a comprehensive river-cleaning system that enables the removal of both floating and suspended litter particles from watercourses withstanding flow variations. The innovative technical cleaning infrastructure is based on a self-cleaning system using rotating screen drum units. In 42 prototype-scale experiments using ten representative plastic particle types (both 3D items and fragments) of five different polymer types, we prove the self-cleaning concept of the infrastructure and define its parameters for the best cleaning performance. Its cleaning efficiency is strongly dependent on the polymer type and shape. The overall cleaning efficiency for 3D items amounts to 82%, whereas plastic fragments are removed less efficiently depending on hydraulic conditions. Adaptions to the prototype can enhance its efficiency. [ABSTRACT FROM AUTHOR]

This study presents a series of acoustic current Doppler profiler (ADCP) measurements, which are converted into suspended load concentrations (SSC). Depending on the particle size distribution (PSD), the sound backscatter and its attenuation are used to determine a theoretical minimal and physical upper limit of the SSC. The SSC are displayed over time and compared with the evolution of the water level during the same time interval. The present study shows that it is possible to have continuous measurements of SSC and water level with a horizontally installed two beam equipped ADCP and discusses the potential of such a continuing times series measurement for application in hydraulic engineering and research. However, the presented data set shows also that the calibration and the filtering of the raw data has to be improved and that further investigations are needed. After data verification, it will be possible to calculate the yearly sediment load and investigate physical behaviour of SSC concentration as a function of water level and discharge.