MEASUREMENT OF SUSPENDED SEDIMENT ON TIDAL FLAT WITH AN ACOUSTIC DOPPLER CURRENT PROFILER

Abstract

Acoustic Doppler current profilers (aDcps) offer the potential for measuring suspended sediment concentration profiles. In recent years, aDcps operating at a few megahertz frequency have been able to measure velocity and backscattered signal profiles with a high degree of temporal and spatial resolution. Moreover, the blanking distance near the transducer becomes short. As a result, the aDcps may attain high-resolution measurements of suspended sediments in the bottom 1-2 m above the bed. However, a modification needs to be made to account for the complex beam pattern close to the transducer (near-field) . In the present study, the backscattered signal of an aDcp operating at 2 MHz is examined. The backscattered signal profiles corrected using the near-field function by Thorne give close agreement with suspended sediment concentration profiles on the tidal flat in an estuary.