The Hydrodynamic Model and Database:

To simulate the hydrodynamics of the region the ADCIRC (Advance Circulation Model for Coastal Ocean Hydrodynamics) model was selected. ADCIRC is a system of computer models for solving time-independent, free-surface circulation and transport problems in two dimensions. It was developed to model tidally and wind-driven circulation in coastal waters, and for forecasting hurricane storm surge and flooding. It has been applied extensively to New Orleans, the most severally threatened coastal region in the country.

Unlike other similar models of the waterways in the metropolitan region, ADCIRC can represent coastal flooding, showing the extent to which floodwaters reach inland and then retreat. To make use of this capability, a unique database had to be developed for the metropolitan region that seamlessly integrates bathymetric and topographic data. Bathymetric data showing water depths and topological data showing land elevations have been developed for different purposes by different government agencies at different times, and they are referenced to different vertical datums. Moreover, both the bathymetric and topographic datums themselves have changed over time. Tidal datum levels change spatially because of spatial changes in tide range, dredging of waterways, and changes in weather conditions, and sea-level rise. Both bathymetric and topographic data were converted to North American Datum of 1983 (NAD 83). Using data from many different sources available in early 2002. Improved data continues to become available due to changing terrain and improved technology (e.g. LiDAR) we anticipate that the combined bathymetric-topographic database will be updated as our interests expand to larger areas and better data becomes available.

When there is a difference between the modeled and the observed, an operational model may enact bias correction - future predictions include a correction offset based on a running average of past observed error. Our group runs ADCIRC as a research model - when there is error we keep that error with the aim of understanding its fundamental cause. This reduces the operational usefulness of our model, but does not silently mask deep rooted problems. In the long run this will lead to better models, with better physics, for all.

Disclaimer: This model is under developmentand predictions for sea level height are for research purposes only. They should never be used for navigational purposes or emergency planning under any circumstances.
The Eppley Foundation for Research, Inc.