As part of the Coastal Storms Initiative (CSI), we present a circulation model of the St. Johns River, Florida. The model is one component of the CSI, an interdisciplinary NOAA project aimed at providing local communities with enhanced tools and resources to help mitigate the hazards of coastal storms. The other components of CSI include new bathymetric surveys, improved oceanographic and meteorological observations, improved prediction of coastal winds and waves, ecological forecasting, risk and vulnerability assessment, outreach and extension, data integration, and data access and standards.

The hydrodynamic model of the river and estuary makes nowcasts and forecasts of water levels, currents, salinity, and temperature and provides a means for the community to view the results. The CSI framework allows the model to interface efficiently within the matrix of state-of-the-art resources needed to provide a comprehensive approach to protecting coastal communities. Two circulation model applications have been used in the evaluation stage of the nowcast/forecast system. The first of these model applications uses the Environmental Fluid Dynamics Code (EFDC) to perform operational nowcasts and forecasts on a daily basis. This model application was originally developed at the St. Johns River Water Management District and thoroughly calibrated for 1995-1998. The model is shared with the Coast Survey Development Laboratory of NOAA for application in daily nowcasts and forecasts.

The other model being examined for use in the St. Johns River is ELCIRC, a finite volume/finite difference baroclinic model for unstructured grids. As the EFDC model is converted into an operational mode, the ELCIRC application is likewise being calibrated to see if the same level of accuracy or better can be attained. ELCIRC offers some benefits that include: 1) an unstructured grid that can easily be modified to add/coarsen refinement where needed; 2) an advection algorithm that permits large time steps and thus affords more grid refinement if necessary; and 3) a natural treatment of wetting and drying. The latter is an important consideration for this CSI pilot study, as flooding from coastal storms is one of the critical hazards that local communities need to address in their mitigation strategies, and EFDC does not have this capability.

The final products from the Coastal Storms Initiative will be unique in providing a seamless consolidated set of resources pooled from a cross-section of NOAA and its partners working together. As these resources are developed for the St. Johns River pilot project, CSI is looking forward to its expansion nationwide. The Columbia River will serve as the next project area in the strategic plan.