Sandwave

A sandwave is a large flow-transverse bedform in sandy, tidally swept shelf seas, with crest-to-crest spacing of roughly tens to hundreds of meters and heights of a few meters. In the Ashley (1990) scheme adopted by SEPM, the term is deprecated in favor of large to very large dune, since flow-transverse bedforms grade continuously from ripples through dunes with no natural size gap. Sandwaves migrate in the direction of the dominant tidal current and reshape with the spring-neap cycle. They are a charted hazard because they change least depths between surveys, so repeat multibeam bathymetry is used to track their crests in approach channels.