Long-Term Performnance of an AWAC Wave Gage, Chesapeake Bay, VA

Evans-Hamilton, Inc. deployed a Nortek AWAC to collect long-term wave and current data in the Chesapeake Bay near Norfolk VA. The gage has been deployed since March of 2006 in approximately 7 meters of water and has been collecting currents profiles at 20 minute intervals and waves every hour. The system is equipped with an Acoustic Surface Tracking (AST) capability which uses a fourth acoustic beam to directly measure the water surface elevation at 4 Hz during the wave data collection burst and provide a water level time series for use in the wave analysis. Over the first 16 months of deployment the instrument has performed well and has not experienced any degradation to its physical components or in the system´s electronics and signal strength. The error statistics for the data collected over the deployment period indicate the instrument has had very few data quality issues even during large wave events. The AST has been shown to be a reliable method of directly measuring critical wave statistics over a long-term deployment even during large wave events. For periods when the AST was not able to provide an accurate water level time series, an alternative method for estimating the maximum wave height based on spectral analysis was considered.