Recent developments in high frequency acoustic backscatter system (ABS) have made possible the development of an acoustic sand ripple profiling system capable of in-situ measurement of sand ripple and microtopography profiles over a 2-3 m length of sea bed. The system has previously been tested under laboratory and estuarine conditions and now, for the first time, under wave conditions. Parameters related to the sea bed roughness have a direct bearing on the re-suspension of sediment and will therefore be of importance to the production of sediment models, which currently rely on a single bed roughness parameter to encompass these effects. The prototype sand ripple profiling system was mounted on a platform, STABLE II, approximately 1.2 m above a sand bed in the Delta Flume large scale facility at the De Voorst site of Delft Hydraulics in the Netherlands. The flume is approximately 5 m wide, 7 m deep and 230 m long. A 0.5 m deep sand bed was covered by 4.5 m of water during a six week series of experiments. The size of the Delta Flume and the range of wave conditions that can be produced within it allow instrument testing to be carried out in conditions that are equivalent to those found in nature. Both regular and irregular waves of period 5 seconds and height ranging from 0.5 m - 1.25 m were used over two separate sand beds with median grain diameters of 0.162 mm and 0.329 mm. Asymmetric waves of periods 4 and 6 seconds with waveheight of 1 m were also used. Profile measurements were taken at approximately 30 second intervals to produce time series of ripple profiles over the full range of wave conditions. Examples of data collected by the sand ripple profiler during these experiments are presented, showing the sand ripple profiles and their evolution under a variety of wave conditions with the two sand beds.
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