CCP-correlation current profiler a comparison between laboratory and field measurements

Over the last six years OCN, mainly as a subcontractor of RIKZ, has developed a new measurement method to determine high-resolution velocity profiles. High-resolution velocity profiles (both temporal order of seconds-and spatial-order of millimetres) can be determined in just the last meter(s) above the sea- or riverbed. Note that the last metre is of special interest since most sediment transport occurs in this distinct layer. The Correlation Current Profiler (CCP) measurement method has been proven accurate to within 1% with respect to laser Doppler reference measurements during tank trials. Coastal and river authorities are generally interested in availability of sediment transport measurement instrumentation for economical reasons (harbours, shipping), environmental reasons (pollution, river engineering) and safety reasons (flooding). Since the CCP measurement method is based upon acoustic backscatter strength, expansion of the CCP from a current measurement instrument to a transport measurement instrument seems obvious, and also turns out to be feasible. Apart from profiles, sediment structures in suspension as well as the morphology of the bed can be determined with the same instrument during the same measurement. Therefore, in September 1997 dredged river sediment has been put into a laboratory flume to simulate a typical Dutch river situation. Since glass walls permitted visual inspection of what was going on, the acoustically detected signature of the sedimentation processes and phenomena can be validated. Since the movement of sediment ripples is also acoustically determined, a closed mass balance between the effective bed motion and the suspended sediment transport will now be possible