Longshore transport of mud by waves: Northeastern coast of South America

Abstract

Time series measurements of waves and wave/mud interactions along the Surinam coast indicate that waves may play a greater role than previously thought in the suspension and transport of fine-grained sediment on the northeastern coast of South America. Accumulations of fluid mud or slingmud that occur on western flanks of migrating mudbanks affect incoming swell by changing their form from sinusoidal to solitary-like and by preventing wave breaking except for occasional spilling. As solitary like waves propagate over the soft-mud bottom, fluid mud is suspended, resulting in surface suspensate concentrations that exceed 3.103 mg/I. The presence of solitary waves, high suspended-sediment concentrations, and a relatively uniform angle of wave approach throughout the year may lead to extraordinarily high sediment transport rates. If waves are assumed to have a net drift as given by solitary wave theory, then, in taking angle of wave approach and actual measured concentration of sediment in suspension, enough sediment can be transported by waves alone to explain the propagation of mudbanks by fluidmud transport. On the basis of reasonable wave and sediment conditions, it is estimated that up to 70.106 m3 of mud can be transported alongshore each year.