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

ABSTRACT 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.