Flocculation of Suspended Sediment in the Fly River Estuary, Papua New Guinea

Eric Wolanski, Ronald J Gibbs


The suspended sediment of the Fly River is mostly fine silt with a mean particle size of 8 µm; the clay fraction makes up less than 20% of the suspended sediment by volume. On reaching brackish water in the estuary, the sediment flocculates. The flocs are small (typical mean size of 30 µm) and are a mixture of fine silt and clay particles, with silt particles dominating. Because of the dominance of silt particles incorporated in the flocs, the flocs are structurally weak and are destroyed by tidal turbulence at spring tides. The clay particles are selectively trapped in the turbidity maximum zone of the estuary.


Floc; turbulence; tidal flow; turbidity maximum zone.

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