This award will support the analysis of the interaction of infragravity-band wave motions (periods 20-200 seconds) and barred topography. Data were obtained during a nearshore ocean field experiment (called SUPERDUCK) in Duck, North Carolina, during the fall of 1986. Theoretical models suggest the importance of these motions in sand bar generation, as well as the potential tuning of infragravity waves by a pre-existing bar. The SUPERDUCK data set is unique in its frequent and thorough sampling of the three-dimensional bathymetry and the local incident (4-20 second) and infragravity wave fields. Three questions will be addressed: 1. Are there systematic differences between infragravity waves and barred beaches and those measured over simpler topographies? 2. If there are differences, what are the dynamical reasons for them?, and, 3. Are infragravity waves responsible for sand bar generation and evolution?
