Bridges with and without piers are prone to large wood (LW) accumulations during floods, possibly resulting in an upstream backwater rise, local scour, or destabilization of the structure. To reduce the flood hazard, measures are required that decrease the accumulation probability p of LW. This paper presents a literature review on existing measures to reduce p at bridges. In addition, a series of flume experiments was conducted to examine structural measures at bridge piers regarding their accumulation risk reduction effect. The objective was to test the efficiency of (1) LW fins and (2) bottom sills including various configurations. The resulting p was then compared to the setup without measures. The tested configurations of a LW fin did not decrease p. Bottom sills, in contrast, are a promising measure to reduce p for a defined range of boundary conditions. The installed sills lead to enhanced turbulence and increased surface waves. The best results to reduce p were obtained with two consecutive sills, leading to an average reduction of p by 30%. In contrast to retaining LW with retention structures, LW can be safely guided downstream, thereby preserving its relevant ecological role in rivers. However, the efficiency of bottom sills strongly depends on the approach flow and the sediment transport conditions.

中文翻译：

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减少桥梁大量木材积聚的风险措施

带有和不带有桥墩的桥梁在洪水期间容易积聚大量木材（LW），可能导致上游回水上升，局部冲刷或结构不稳定。为了减少洪水灾害，需要采取措施来降低LW的累积概率p。本文介绍了有关减少桥梁p的现有措施的文献综述。此外，进行了一系列的水槽实验，以检查桥墩在结构上的措施，以降低其累积风险。目的是测试（1）LW散热片和（2）底梁（包括各种配置）的效率。然后将所得的p与不进行测量的设置进行比较。LW鳍的测试配置没有降低p。相比之下，底梁是在定义的边界条件范围内减小p的有前途的措施。安装的门槛会增加湍流并增加表面波。减少p的最佳结果是连续两个门槛，使p的平均减少了30％。与用保留结构来保留轻水相比，轻水可以安全地向下游引导，从而在河流中保持其相关的生态作用。但是，底槛的效率在很大程度上取决于进场流量和泥沙输送条件。