In-channel wood is a key component in fluvial ecosystems; however, transport of inchannel wood during floods can create hazards in urbanized areas. Among the main problems is wood accumulation at bridges, which reduces flow openings, causes blockage and inundation of nearby areas and, eventually, results in structures collapsing. Increasing awareness of the importance of the ecological role of wood in rivers calls for a compromise between the preservation of river ecosystems and management strategies for the prevention of wood-related hazards. In recent years, knowledge related to in-channel wood dynamics and hazards has notably increased, and a significant body of valuable information can be found in an extensive number of studies. This review provides a comprehensive summary of the most relevant advances regarding in-channel wood-bridge interactions. We review the factors controlling wood accumulation formation and summarize the different approaches used to analyse this process, namely, physical and numerical modelling. Finally, we conclude by highlighting the most important knowledge gaps, addressing particularly underresearched fields and stressing the remaining challenges.

Streamwood accumulation at bridges exerts additional forces to bridge structures and may aggravate flooding, local scouring, and eventually may lead to bridge collapse. However, the important ecological role of streamwood in fluvial systems calls for a compromise between preservation of river ecosystems and prevention of streamwood‐related hazards (e.g., bridge clogging). This study evaluates the effect of bridge pier shape on wood accumulation or blockage, probability in lowland type of rivers. We conducted laboratory experiments in a flume testing various pier shapes and wood transport mechanisms under two different flow conditions, complemented with numerical modelling. Results revealed that the flow field immediately upstream from the pier has a significant influence on the blockage probability. The pier shape is controlling the flow field, thus, it has a significant influence on wood accumulation. In particular, a squared pier shape, higher Froude number and semi‐congested wood transport resulted in the highest blockage probability under the tested conditions. Our results may help to better design infrastructures to mitigate streamwood‐related hazards in rivers.

a b s t r a c tA new higher order 1D numerical scheme for the propagation of flood waves in compound channels with a movable bed is presented. The model equations are solved by means of an ADER Discontinuous Galerkin explicit scheme which can, in principle, reach any order of space-time accuracy. The higher order nature of the scheme allows the numerical coupling between flux and source terms appearing in the governing equations and, importantly, to handle moderately stiff and stiff source terms. Stiff source terms arise in the case of abrupt changes of river geometry such as in the case of hydraulic structures like bridges and weirs. Hydraulic interpretation of these conditions with 1D numerical modelling requires particular attention; for instance, a 1st order scheme might either lead to inaccurate solutions or impossibility to simulate these complex conditions. Validation is carried out with several test cases with the aim to check the scheme capability to deal with abrupt geometric changes and to capture the direction and celerity of propagation of bed and water surface disturbances. Validation is done also in a real case by using stage-discharge field measurements in the Ombrone river (Tuscany). The proposed scheme is further employed for the computation of flow rating curves in cross-sections just upstream of an abrupt narrowing, considering both fixed and movable bed conditions and different ratios of contraction for cross-section width. This problem is of particular relevance as, in common engineering practice, rating curves are derived from stage-measuring gauges installed on bridges with flow conditions that are likely to be influenced by local width narrowing. Results show that a higher order scheme is needed in order to deal with stiff source terms and reproduce realistic flow rating curves, unless a strong refinement of the computational grid is performed. This capability appears to be crucial for the computation of rating curves on coarse grids as it allows the modeling of abrupt contractions and jumps in bed bottom elevations, which often occur near cross-sections where stage measuring gauges are installed.

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