Advanced Hydrodynamic Models for Tide and Storm Predictions: A High-Resolution Channel to Basin-Scale Unstructured Grid for the US East and Gulf of Mexico Coasts

NOAA’s Extratropical Surge and Tide Operational Forecast System (ESTOFS) for the US East and Gulf of Mexico coasts spans across the western North Atlantic and applies an unstructured heterogeneous triangular mesh. ESTOFS uses ADCIRC, a robust high-fidelity coastal ocean circulation model, widely used by the coastal community for tides, storm surge, and wave-induced coastal setup. ADCIRC uses a continuous-Galerkin based finite element unstructured mesh framework that allows a highly variably-sized resolution to better represent the complexity of the ocean, shelf and nearshore hydrodynamics, and geometry.

The current operational version of ESTOFS uses a sub-optimal unstructured mesh that over-resolves some straight portions of the coastline but under-resolves complex estuaries and coastal features. While the current ESTOFS model is efficient in terms of computational run time since it was specifically designed for operational use, its accuracy is suboptimal as the details of the complex inland water bodies are not captured with the 200 m minimum mesh resolution. Recent advances in mesh generation tools now allow generating replicable high-resolution (minimum resolution ~50-m) meshes in much shorter times than the hand-edited processes used to develop the current version of ESTOFS. This opens the opportunity to study the effect of different resolution strategies to represent topo-bathymetric and far inland water body features, in order to reduce the computational cost and improve the accuracy of the models. Thus, the objective of this research is to develop an ADCIRC-based model to more accurately and efficiently simulate the dynamics of the coastal ocean and riverine system for the US Atlantic and Gulf of Mexico coasts for tide/storm/wave setup predictions.

The new ADCIRC-based model will incorporate a representation of the riverine system far up to the point where the ocean has no effect on water levels, efficiently reduce the minimum grid-size from 250 m to 50 m with no significant increase in the number of nodes, and will combine pseudo-quadrilateral elements to represent narrow channels. This new generation of ESTOFS will represent a significant enhancement of the current technology for tides, storm surge, and wave setup prediction, but also will set up the required conditions for future approaches focused on coupling inland hydrology to the coastal modeling.