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Simulating WAves Nearshore (SWAN)
The SWAN (Simulating WAves Nearshore) model is a spectral wave model developed at the Delft University of Technology, The Netherlands. SWAN models the energy contained in waves as they travel over the ocean surface towards the shore. In the model, waves change height, shape and direction as a result of wind, white capping, wave breaking, energy transfer between waves, and variations in the ocean floor and currents. Initial wave conditions, including wave height, wave direction and wave period (time it takes for one wavelength to pass a fixed point), are entered into the model, and the model computes changes to the input parameters as the waves move toward shore. Model results are computed on a 500-m by 500-m grid for the area of research. Model output information (wave height, wave direction, and wave velocity) is produced for each cell in the model grid, and can be displayed in a map view to simplify visualization of changes in waves over the study area.
Waves play an important role in moving sediment throughout the Columbia River littoral cell, influencing the patterns of erosion and accretion along the coast, and ultimately shaping the shoreline. Wave models are important when studying a large coastal area. The expense of collecting in situ wave measurements, by installing multiple wave buoys, may be cost prohibitive. SWAN makes it possible to model waves over a large area, for any boundary input, in a cost-effective method, and results can be obtained in a relatively short period of time.
Conclusions
- The SWAN model produces the best results on the Southwest Washington inner continental shelf when all formulations are set to model defaults except: wind input / whitecapping formulation is the Janssen formulation, with CDS2 = 4.5, d = 0.5, and the bottom friction is calculated with the Madsen formulation, Kn = 0.05 m.
- The SWAN model reproduces field conditions well when the model is properly initialized.
- The SWAN model was only properly initialized for this experiment when waves and wind originated offshore of the model boundary.
- Peak direction at the NOAA buoy 46005 calculated from peak direction at the CDIP buoy using Snell’s Law is not valid when offshore peak direction is influenced by winds from onshore.
The following publications provide additional information about the SWAN model:
- SWAN wave model sensitivity to variation in model formulation
- Application of the SWAN wave model to a high-energy continental shelf (4.3 MB)
