SUSPENSION AND TRANSPORTATION OF FLUID MUD BY SOLITARY-LIKE WAVES

Abstract

The suspension and transportation of fluid muds in the nearshore zone by shallow-water, solitary-like waves has been investigated along the coast of Surinam, South America. Accumulations of fluid mud which front the coast at a spacing of 30-60 km affect incoming swell by changing the wave profile from sinusoidal to solitary-like and by preventing wave breaking except for occasional spilling. Simultaneous time-series measurements of wave height and period, fluid-mud density, and tide elevation, along with results of suspended-sediment measurements, indicate that in cases when the bulk density is less than 1.20 g/cm and where water depths are less than 5 m fluid mud is suspended from the bottom in two frequency modes: wave-by-wave suspension (-10 sec) and tide related suspension (-12.4 hr) . Surface-water suspensate concentrations exceed 3.4 x 10 mg/1 as up to 0.5 m of fluid mud is periodically removed from the bottom. High concentrations of suspended fluid mud, together with solitary-like waves from the northeast throughout the year, can lead to extraordinarily high sediment transport volumes. Calculations based on solitary wave theory and on data obtained from this ft ^ study indicate that 15-65 x 10 m of mud can move along shore each year without involving breaking waves, the concept of radiation stress and a nearshore circulation cell, or bed-load transport. These values are 10 to 100 times greater than typical transport rates along sandy coasts.