Modelling cross-shore shoreline change on multiple timescales and their interactions Schepper, R. /Almar, Rafaël Bergsma, E. de Vries, S. Reniers, A. Davidson, M. Splinter, K. equilibrium shoreline modelling ShoreFor cross-shore sediment transport multiple timescales In this paper, a new approach to model wave-driven, cross-shore shoreline change incorporating multiple timescales is introduced. As a base, we use the equilibrium shoreline prediction model ShoreFor that accounts for a single timescale only. High-resolution shoreline data collected at three distinctly different study sites is used to train the new data-driven model. In addition to the direct forcing approach used in most models, here two additional terms are introduced: a time-upscaling and a time-downscaling term. The upscaling term accounts for the persistent effect of short-term events, such as storms, on the shoreline position. The downscaling term accounts for the effect of long-term shoreline modulations, caused by, for example, climate variability, on shorter event impacts. The multi-timescale model shows improvement compared to the original ShoreFor model (a normalized mean square error improvement during validation of 18 to 59%) at the three contrasted sandy beaches. Moreover, it gains insight in the various timescales (storms to inter-annual) and reveals their interactions that cause shoreline change. We find that extreme forcing events have a persistent shoreline impact and cause 57-73% of the shoreline variability at the three sites. Moreover, long-term shoreline trends affect short-term forcing event impacts and determine 20-27% of the shoreline variability. 2021 text https://www.documentation.ird.fr/hor/fdi:010082246 fdi:010082246 Schepper R., Almar Rafaël, Bergsma E., de Vries S., Reniers A., Davidson M., Splinter K.. Modelling cross-shore shoreline change on multiple timescales and their interactions. 2021, 9 (6), 582 [27 p.] EN AUSTRALIE VIET NAM NOUVELLE ZELANDE