Geology Reference
In-Depth Information
Fig. 9.5
Thematic plots of tidal flats in the different coastal sys-
tems with varying sediment input and wave exposure (
a
-
f
).
1
- bar-
rier island,
2
- salt marsh,
3
- bare intertidal flat,
4
- lagoon,
5
- ebb
tidal delta,
6
- flood tidal delta,
7
- rocky coast,
8
- tidal channel/
creek,
9
- rocky island,
10
- bay-head delta,
11
- tidal sand ridge/
bar,
12
- sand beach,
13
- gravel beach,
14
- chenier ridge
sitional and wide tidal flats along the south bank
(Fig.
9.7
; ECCE
1992
; Fan et al.
2005
). Constrained
flows in the main channels of estuaries and deltaic
distributaries are usually shore-parallel and ebb domi-
nated, gradually changing into shore-normal direction
and flood domination as they flow over the intertidal
flats. Shore-normal tidal flow is generally quite weak
due to limited tidal prism over the intertidal flats. The
velocities of flood flows decrease from the subtidal
zone to the upper intertidal flat owing to the shoaling
effect. For example, the spring flood flow velocities
decreased from 0.86 cm/s at a subtidal station (−2 m,
elevation referred to Wusong Datum), 0.49 cm/s at
0 m, to 0.35 cm/s at an intertidal station (+2 m) on the
Nanhui Mudbank in the Changjiang Delta (Li
1990
).
The open-coast tidal flats are highly exposed to
wave impact, and they are potential to change from the
tide-dominated setting temporally (a few hours to
days) or seasonally into the wave-dominated setting,
especially where they are highly affected by the
