W. Vanleussen et Jm. Cornelisse, THE DETERMINATION OF THE SIZES AND SETTLING VELOCITIES OF ESTUARINE FLOCS BY AN UNDERWATER VIDEO SYSTEM, Netherlands journal of sea research, 31(3), 1993, pp. 231-241
The in situ underwater video system VIS is described. VIS determines s
izes and settling velocities of suspended mud flocs without destroying
the large fragile aggregates. The settling process of the flocs and a
ggregates can be observed directly on a screen on board the research v
essel. Analysis of the videorecordings was possible up to 600 mg.dm(-3
), which is of importance in turbid estuarine systems. Experiments wit
h VIS in the Ems estuary showed macroflocs with settling velocities of
0.5 to 2.0 mm.s(-1) and sizes of 200 to 500 mu m. These flocs were ob
served at relatively low suspended-sediment concentrations (20 to 50 m
g.dm(-3)). During certain phases of the tidal cycle (around mid-tide)
even larger aggregates were observed with dimensions in the range of 4
00 to 1100 mu m and settling velocities of 1 to 7 mm.s(-1), surviving
relatively high current velocities. The large aggregates are shown to
play an essential role in the phenomenon of rapid settling, as observe
d in various estuaries.