Replacing a third-generation wave model with a fetch based parametric solver in coastal estuaries

Abstract

Within a restricted estuarine environment, the use of third-generation wave models for predicting wave heights can be computationally expensive, signaling a need for model development that reduces the computational costs of existing coupled hydrodynamic models. This study focuses on the development and testing of a parametric wave solver that incorporates four wave height formulations (SMB, SPM, TMA, and CEM) for predicting wave properties in a restricted estuarine environment. The emphasis is on improved efficiency without affecting accuracy, allowing for ensemble wave-surge forecasting to be performed on desktop computational resources. Evaluation of the performance of the parametric solver is twofold, first the parametric solver is compared to a third-generation wave model, Simulating Waves Nearshore (SWAN), for the Indian River Lagoon domain, which lies on Florida's east coast. Then both the parametric solver and SWAN are compared to in-situ ADCP wave data at a point in the estuarine domain. The creation of three different synthetic wind fields allows for model comparison, with wind fields permitting testing of the parametric model in order to reproduce (1) fully developed conditions, (2) wind speed variability, and (3) wind direction variability in tropical storm level wind events. For consistency comparison, wave height solutions over the same domain are generated by SWAN and the parametric models. Comparisons made between the parametric model performance and SWAN show a 4-member parametric model is accurate to within 87% globally, with a runtime improvement of over two orders of magnitude compared to SWAN. The parametric model's ensemble average wave height solution was 5.5% less than the in-situ measured wave height; the SWAN solution was 5.5% greater than the measured wave height at the same location. Therefore, the parametric wave model proves to be a viable alternative to running an expensive third-generation wave model for predicting waves in an enclosed estuarine system.