Author(s): Heide Friedrich; Bruce W. Melville; Stephen E. Coleman; Vladimir Nikora; Thomas M. Clunie
Keywords: Submerged bed forms; Three-dimensional measurements; Sediment; Dune; Ripple; Uultrasonic depth sounder
Abstract: A new technique for measurement and analysis of the development of three-dimensional bed forms is reported. Conventionally, laboratory bed forms are often assumed to be two- dimensional and described using longitudinal bed profiles measured along the centre-line of the flume. Seatek’s multiple transducer arrays (MTAs) allow bed forms measurement along many profiles in spatial or temporal domain or in both, which may be transformed into a three-dimensional field of bed elevations. Measuring bed forms at a fixed position in the flume provides a comparison of the downstream migration of neighbouring bed forms, a technique termed stationary measurement herein. The ability to move the transducers along different sections of the flume results in a continuous area of bed observation, herein termed moving measurement of bed forms. The use of the MTAs is described, including specific aspects which need to be taken into account for their successful application. Verification of the accuracy of the measurements is given. Experimental runs were carried out in a 440mm- wide, glass-sided, 12m-long laboratory flume. The sediments used were a fine sand with d50 = 0. 24-mm and a coarse sand with d50 = 0. 8-mm. The study is part of a series of studies looking at the phenomenon of submerged sediment bed form behaviour.