Application of a high resolution acoustic scanning system for imaging sea bed microtopography

The application of multifrequency acoustic backscattering to the measurement of nearbed suspended sediment dynamics is a technique that is increasingly becoming accepted by sedimentologists. These systems provide detailed information on the suspension, but only limited data on the bed. Since it is the interactions between the flow dynamics and the bed forms that lead to the entrainment of the sediments into suspension, measurements of the bed features are an essential component in developing a framework for understanding suspension processes. Most theoretical predictions of suspended sediment profiles require a knowledge of the sea bed form, for example is the bed plane or rippled, and if the latter, what is the amplitude and wavelength of the ripples. To date the input of this parameter has been somewhat problematic because of the difficulty of obtaining such measurements. In the present work, results are reported on the development and deployment of a high frequency, 2 MHz, scanning system used to profile sea bed microtopography. The ability of such systems to provide the required subcentimetre resolution has been examined, and results from laboratory and marine studies are reported