The near shore coastal ocean (0-5 miles) is the most heavily used part of the vast ocean. Accurate wave forecasting can increase safety in this area for boaters, fishermen and recreational users. Currently, forecast models exist to simulate wave activity in the deep ocean environment. WaveWatch III (WWIII) is a deep ocean model used for forecasting wave activity beginning 20 nautical miles from shore. WWIII is not equipped with shallow water physics, meaning it cannot be accurately applied to coastal waters. The near shore coastal ocean requires a more specialized wave and current model. Recently, wave models have been developed specifically for near shore forecasting. SWAN (Simulating Wave Near Shore), developed at Delft University in the Netherlands, was first used for marine forecasting by the Eureka National Weather Service Office in California as an answer to the near shore model shortcoming.
The SWAN model was applied to the entrance to Humboldt Bay Harbor and has become a valuable tool for local mariners navigating these dangerous waters. Evidence of SWAN’s accuracy has been mostly provided by human observation. While anecdotal validation is useful, a more scientific evaluation is needed. This project proposes to scientifically evaluate the effectiveness of SWAN in comparison to other coastal wave models.
This multi-agency partnership is a collaboration between the UNC Coastal Studies Institute (UNC – CSI), UNC Institute of Marine Sciences (UNC – IMS) and Field Research Facility of the Army Corp of Engineers (USACE) with MORPHOS. This project will compare the performance of two distinct coastal wave models: SWAN and STWAVE (STeady STate WAVEs developed by USACE) and is currently being applied over North Carolina’s coastal waters, inlets and sounds. The more accurate model will be coupled with a circulation model, ADCIRC (ADvanced CIRCulation) and the results evaluated.
Led by Jeffrey L. Hanson, research oceanographer at USACE and Eve Devaliere, UNC-CSI and USACE research scientist, the project focuses on five research domains; Chesapeake Bay, Outer Banks, Onslow Bay, Long Bay and the outer regions. Forecasting models produce files representing information such as depth, wave height and energy spectrum. The data is then formatted so that one can compare results between models and visual observations. “The ultimate goal is to couple an accurate wave model with an atmospheric model, sediment transport model and a current model, so that the entire coastal phenomenon can be reproduced, analyzed, simulated and forecasted.”, states Devaliere.
The practical application of this work will help protect our valuable coastline. In order to design appropriate shore protection, accurate wave model validation is essential. Once validated, this research will help USACE to build and recommend appropriate shoreline protection measures and in turn make our coasts safer from damaging catastrophic events such as hurricanes and nor’easters. “Not doing this validation would be like not having a crash test after building a car,” says Devaliere, “it [SWAN] seems to run great but we are not sure of the reaction in extreme conditions. Hurricane Katrina taught us that existing wave models are not sufficient to predict the effects of major hurricanes on the coast.” Ocean wave forecast models are a tool for everyone from fisherman to surfers and recreational boaters. Accurately forecasting waves could help prevent accidents and disasters. Public safety concerns are not the only issues this model can be applied to. The near shore model can be used daily for weather and wave forecasting by the weather service. Researchers can use information gathered to determine how sediment transfer affects marine life in coastal and estuarine waters. The need of this study and application of the results has the potential to greatly benefit everyone in coastal communities from residents and tourists to scientists and resource managers.
View the USACE-FRF's Wave Model Here