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FIGURE 12.14 Computed variation in settling velocity. (Subtract 1000 min from time axis to compare with Figure 12.11.)

FIGURE 12.15 Computed variation in flocculation time. (Subtract 1000 min from time axis to compare with Figure 12.11.)

FIGURE 12.15 Computed variation in flocculation time. (Subtract 1000 min from time axis to compare with Figure 12.11.)

around LWS is probably due to the large stratification at that time. Only during MFV equilibrium floc sizes are predicted.

Further, it is important to note that during rising tide (flood), larger settling velocities are found in the upper part of the water column, whereas during falling tide (ebb), larger settling velocities are found near the bed. This results in a destabilizing effect on the vertical concentration profile during flood. The stabilizing effect during ebb enhances the sediment-induced buoyancy effects, resulting in the stratified conditions during ebb. The floc size, hence settling velocity, is governed by the turbulence intensity, parameterized by G and the suspended sediment concentration c (Equation (12.8)). Apparently for the current conditions, the effect of turbulence ("G-effect") is dominant during flood, whereas the effect of concentration ("c-effect") is dominant during ebb.

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