Assessing Debris-induced Scour at Bridge Piers in Real-world Practice: A Case Study

Large wood accumulations at bridge piers substantially contribute to exacerbate localised pier scour, which can undermine the pier foundations and may have catastrophic effects such as pier damage and bridge collapse. Recent experimental research showed that the increase in scour depth can be estimated through an additional factor in the typical scour depth formulae widely used worldwide. Nevertheless, a systematic application of this methodology has never been attempted. In this work, a masonry bridge in Devon (UK) has been used as a representative example for the estimation of the scour depth at bridge piers. For a range of flood events, the increase in local scour depth has been observed between 40 and 60% more than the scour hole depth without accumulated debris. The scour risk of the bridge has also been assessed in relationship to the bridge vulnerability. To this end, a debris vulnerability factor was included, showing that bridges liable to debris accumulations will have a substantially higher risk than other structures. The results shown in this work will pave the way for a systematic and self-consistent application of the scour assessment to structures that is inclusive of the effects from debris accumulations.