An equilibrium model to predict shoreline rotation of pocket beaches

• New beach-evolution model was developed for estimating the beach rotation.
• Shoreline rotation at Barcelona beaches is reproduced with an RMSE less than 1.5 m.
• The model predicts efficiently the shoreline rotation over a complete range scale.

A novel and simple beach-evolution model for estimating shoreline rotation at sandy pocket beaches is presented. The model is based on the assumption that the instantaneous changes to the planview shape of the shoreline depend on the long-term equilibrium planview shape. Two years of shoreline observations extracted from video images of three artificially embayed beaches of Barcelona and hourly wave timeseries are used to validate the model. Numerical model results and field observations show an excellent agreement with an RMSE less than 1.5 m. The model successfully reproduced the shoreline response over a range of scales (months and years). Because of its simplicity and its computational efficiency, the model provides a powerful tool to understand the dynamics regulating the evolution of pocket beaches and predict temporal patterns in beach rotation.