A Lagrangian model of wave-induced beaching and resuspension of plastic particles

In most Lagrangian models for plastic transport in the ocean, interactions between particles and shorelines are either completely ignored or overly simplified, despite it being well-known that coastlines are often temporary harbours rather than permanent sinks for plastic pollution. We present a model for beaching and resuspension that is able to capture more detail, in particular spatial and temporal variation in beaching and resuspension dynamics. Our model is a stochastic wave-based model, with a probability parameter that can be adapted to fit the model to observations. We discuss how reported observations from field studies on beaching and resuspension of plastic can be represented using this parameter, but we emphasise that this is a complicated process that needs further research before a complete parameterisation can be provided. To inform model development, we also studied the beaching dynamics of one type of plastic pellets on an artificial beach in a wave flume. We tested our model against the observations and found that, overall, the model is capable of reproducing the observations to a satisfactory degree. We believe that our model is a good starting point for further model development and understanding of beaching and resuspension dynamics improves.