A simplified method to predict sandbar migration: The Duck, NC case

Sandbars in the nearshore region provide protection to the beach by dissipating wave energy. Hence, a better understanding of the response of sandbars to varying wave climates has important implications for coastal protection, human activities (e.g., industry, tourism, research, and surfing) and military activities. Successful modeling of sandbar behavior is challenging due to the complex hydrodynamics processes which drive sediment transport and morphological changes. It is understood that offshore sandbar migration is predominantly due to offshore-directed currents (undertow) while wave skewness and asymmetry favor shore-ward bar migration. Many approaches have been proposed to model sandbar migration. Finely tuned wave-averaged models have been shown to have some predictive capabilities for single sandbar migration cases, but they have poor predictive skills when applied for other sandbar migration cases. Here we propose a simplified model for evaluating sandbar migration. Our model takes wave-averaged parameters as input, but computes non-wave-averaged sediment transport processes using a reconstructed wave signal. This method explicitly solves for the sediment transport due to wave acceleration skewness and velocity skewness, avoiding parameterizations usually implemented in phase-averaged models. This work focuses on data collected at the Field Research Facility in Duck, NC. The proposed method is capable of successfully modeling the bar evolution over multiple cases. The model is a useful tool for coastal managers and researchers to forecast sandbar migration under different hydrodynamic conditions.