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and the equlibrium floc size in the lower part of the water column Dl follows from (12.8):

The settling time of large flocs in the upper part of the water column Ts is found from Equation (12.5):

ws a Du where Du is the floc size in equilibrium with Gu and a" is defined before. If the relative flocculation time Tf/Ts < 1, we expect that considerable aggregation can take place so that flocs higher in the water column are much larger than those near the bed. Substitution from Equation (12.15) through (12.18) yields Tf/Ts:

Ts kAchGuV Gu \hc2ul where we use the various parameter values obtained for Ems mud. The relative flocculation time Tf/Ts is depicted in Figure 12.8 for a variety of suspended sediment concentrations, showing under which conditions considerable vertical gradients in

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