A Relic Sand Wave Field in a Tidal Channel

A sand wave field in the eastern flood channel of Moriches Inlet was monitored for eight weeks during the summer of 2005. Bathymetric data show sand waves which are 15 m long and 39 cm tall with shallow slip faces. These sand waves remained stationary over the eight week study. Analysis based on work by van Rijn and Yalin suggests that these sand waves were created when the current velocity reaches 80 cm/s. However, the peak current speeds recorded during this study are less than 60 cm/s. Infrequent, high-energy events are believed to have created these sand waves. A hypothetical event creating these sand waves is described based on a linear analysis of tidal range and peak tidal currents. Water level data from Sandy Hook, NJ and Shinnecock Inlet, NY are used to identify this event. This study demonstrates that episodic events may control sand wave morphology and that once emplaced the sand waves become autonomous.