ROTARY SIDESCAN IMAGES OF NEARSHORE BEDFORM EVOLUTION DURING A STORM

High resolution acoustic images are presented of bedform development o n the crest of a nearshore bar during a storm. The images were obtaine d using a 2.25 MHz rotating sidescan sonar. The sonar system provides a continuous record of the evolution of the bedform field through time , within a 10-m diameter field of view. The images document the occurr ence of ripples, cross ripples, and megaripples. During the waning sta ges of the storm, transitions among ripple types occurred on time scal es of 1-3 h, beginning with flat bed and culminating in highly 3-D sho rt-crested ripples.