Remotely sensing in detecting the water depths and bed load of shallow waters and their changes

Bed load is a type of sand drift and accumulation on the sea-bed. Sand drift is a very important index to survey the erosion or deposition of coastal zone. The change of water depths indicates the change of bed load in shallow waters. The conventional method for measuring water depth uses the shipboard echo sounder, which is accurate for point-measurement, but is a time-consuming and labor-intensive task. For periodic survey of bathymetry as synoptic scale, the remote sensing method may be a viable alternative. Wave spectrum bathymetric (WSB) method takes advantages of remote sensing to obtain the bathymetry of shallow waters safely, economically and quickly. The WSB method is feasible to detect the change of water depths over coastal zones where water depths are less than about 12 m. This remote sensing method is worthy to be well developed and efficiently applied to change detection of water depths and bed load in shallow waters.