Bridge Clogging by Loose Sediment in Mountain Streams: A Practical, Physics‐Based Numerical Approach for Use in Hazard Mapping

The clogging of bridges by loose sediments is a phenomenon that has so far been little studied in the literature but plays a decisive role in determining the spatial distribution of hazards in mountainous areas affected by these events. Lacking a systematic approach, in this paper, we propose a simple scheme describing the physics of bridge clogging derived from some field evidence, identify the requirements that a mathematical-numerical model must fulfill to be able to implement the scheme, show how the TRENT2D model matches these requirements, and how it is possible to practically implement a procedure for simulating a bridge clogging event. The application to a study area has shown reasonable results, especially regarding hazard mapping. Furthermore, although it was impossible to carry out an in-depth validation, the proposed approach appears preferable to simplified approaches, such as neglecting the presence of the bridge and its possible clogging or using fixed-bed modeling with a given increased discharge compared to the liquid estimation. Further investigations will be performed based on field and laboratory data to make the approach even more reliable.