Sensitivity of Delft3D to Input Conditions

In January 2009, the forecasting ability of the Delft3D modeling suite was demonstrated in real time for an area in the Northern Gulf of Mexico. As part of the demonstration, a bathymetric survey was conducted, and several wave buoys of different types were deployed. Delft3D is a three-dimensional modeling suite that can also be run in depth-averaged mode to provide wave conditions, currents, changes in morphology, or a combination of these processes. Each process is modeled by a specialized module at a range of spatial scales that vary from tens of kilometers to meters. The depth-averaged model was configured for the area of interest (AOI) located on Santa Rosa Island in the vicinity of Navarre Beach, Florida. The wave and flow modules were coupled, allowing for wave-current interactions resulting in wave- and tide-driven currents. Comparisons between estimated and measured wave parameters showed an underestimation in wave height, which lead to a sensitivity analysis to determine how changes in the bathymetry, wind input, and wave boundary conditions affect the Delft3D output. It was determined that although the wave and current conditions showed some sensitivity to more highly resolved bathymetry, the wave predictions were not improved much by using the updated bathymetry. This is likely because the bathymetric shape of the coastline near Navarre is simple and linear and sensor location was arbitrarily chosen; alternative locations in the AOI showed a greater sensitivity to bathymetry. The Delft3D results were much more sensitive to wind input and wave boundary conditions in this particular application. The authors present the sensitivity of wave results to changes in the model configuration with respect to the model parameters discussed in addition to the improvements rendered by the changes. Although data limitations inhibit a validation of the flow module, sensitivity of the flow module to the changes in the wave conditions will be discussed.
Presented at the Oceans '09 MTS/IEEE Conference on "Marine Technology for Our Future: Global and Local Challenges" held in Biloxi, MS on 26-29 Oct 2009.