396
13 Transport and Mixing in Coastal Ecosystems
~ 40
~
.5 30
] 20
'"
]10
'"tl
0
r::
~
0..
'"
d~
40
30
20
10
0
70
80
90
100
110
120
130
Time (h)
Fig. 13.2: Comparison of observed (solid lines) and predicted (dashed lines) water
flow and sediment transport characteristics in Jiaojiang River Estuary at spring tides:
a velocity at 1.75 m above sea bed, and suspended sediment concentration at b 1.67
m, c 0.55 m, and d 0.35 m above sea bed (adapted from Guan et al., 1998)
of fine sediments into the sea (Yang, 1998). More than half of the sediment
from the river is deposited in the estuary. As a result, wetland area is accreting
at a rate of 15-20 km 2 /year.
A level of turbidity and suspended sediment concentration, similar to that in
Jiaojiang River Estuary, was observed in the Fly River Estuary, Papua New
Guinea (Wolanski and Eagle, 1991; Wolanski et al., 1995). High turbidity in the
saline region of the estuary appears to be due to the simultaneous occurrence of
tidal pumping and the baroclinic circulation due to freshwater discharge which
varies little seasonally.