Bridge pier shape influence on wood accumulation: Outcomes from flume experiments and numerical modelling

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.