A SIMPLE SYSTEM FOR LASER-ILLUMINATED VIDEO IMAGING OF SEDIMENT SUSPENSION AND BED TOPOGRAPHY

A simple underwater video system has been developed for simultaneously imaging sediment suspension and monitoring bed profiles under waves a nd combined wave-current hows, This consists of a diode-laser-generate d light plane and a a black-and-white underwater video camera, The las er light illuminates suspended material in section and also provides a bed profile at the bottom, Orthogonal laser/camera pairs are used to obtain both cross-shore and alongshore views. During deployments, the system has been augmented by acoustic backscatter devices for measurem ent of sediment concentration, As with all video techniques, visibilit y is a limiting factor, but where turbidity is low to moderate, the re sults are encouraging, Results on cross-shore and alongshore bed eleva tion variations and suspension event scales obtained with the video/la ser system are presented for two experiments: one at the National Rese arch Council wave Research Flume in Ottawa, Canada, and the other in t he field at Queensland Beach, N.S., Canada.