|The sediment threshold over tidally induced megaripples|
Black, K.P.; Healy, T.R. (1986). The sediment threshold over tidally induced megaripples. Mar. Geol. 69(3/4): 219-234
In: Marine Geology. Elsevier: Amsterdam. ISSN 0025-3227, more
Bed forms; Marine geology; Ocean floor; Prediction; Ripple marks; Sediment transport; Sedimentation; Marine
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Formulae to predict the initiation of sediment transport over bedforms are derived and field tested. Unlike a Shields-type curve which is valid only for plane beds, both the form drag and skin friction are accounted for. The method relies on successful isolation of the skin friction component of the flow energy losses from the total loss which includes an ineffective form drag component. This is achieved using the Vanoni and Hwang equation for form drag losses while the skin friction is taken from the Yalin sediment threshold curve for plane beds. In conjunction, formulae are derived for the total friction velocity and the speed at 1 m above the bed at the sediment threshold. The theory is tested using thresholds measured in mesotidal estuaries.