Geology Reference
In-Depth Information
c
:
depth averaged concentration (dimensionless
for volume concentration, kg/m
3
for mass
concentration)
a
2
:
empirical coefficients used in suspended sedi-
ment concentration profile modeling (dimen-
sionless)
D
:
sediment grain size (m)
b
:
empirical coefficients used in suspended sedi-
ment concentration profile modeling (dimen-
sionless)
D
*
:
dimensionless sediment grain size (dimension-
less)
D
w
:
wave-energy dissipation due to breaking
(kg/s
3
)
H
s
:
sediment mixing coefficient
q
:
Shields parameter (dimensionless)
d
m
:
mean sediment grain size (m)
q
c
:
critical Shields parameter (dimensionless)
d
50
:
50th percentile sediment grain size (m)
q
crs
:
critical Shields parameter for sediment
suspension (dimensionless)
E
:
wave energy per unit water volume (kg/s
2
)
f
c
:
bottom friction coefficient (dimensionless)
N:
Von Karman's constant, typically taken as 0.4
(dimensionless)
H
:
wave height (m)
h
:
water depth (m)
P:
an efficiency factor to incorporate the influ-
ence of bedforms on bedload transport used in
the Meyer-Peter and Mueller (
1948
) bedload
transport formula (dimensionless)
k
d
:
empirical coefficients used in suspended sedi ment
concentration profile modeling (dimensionless)
k
x
:
dispersion coefficient in
x
direction (dimen-
sion less)
n
:
kinematic viscosity (m
2
/s)
k
y
:
dispersion coefficient in
y
direction (dimen-
sion less)
U
s
:
sediment density (kg/m
3
)
r
w
:
density of water (seawater in the case of tidal
environment) (kg/m
3
)
L
:
wave length (m)
L
s
:
turbulent mixing length (m)
t
b
:
bed shear stress (N/m
2
)
Q
b
:
volumetric bed-load transport rate (m
3
/m/s)
t
c
:
critical bed shear stress (N/m
2
)
q
s
:
volume rate of suspended sediment transport
(m
3
/m/s)
f
:
flocculation factor (dimensionless)
floc
h
f
:
hindered settling factor (dimensionless)
S
= source and sink terms
s
:
sediment specific density =U
s
/U
w
(dimension-
less)
2.1
Introduction
T
:
wave period (s)
U
G
:
near bottom wave orbital velocity (m/s)
Coastal sedimentology and morphodynamics are con-
trolled by a variety of interactive factors, including forces
from ocean tides and waves, trends and rates of sea-
level changes, sediment supply, climatic and oceano-
graphic settings, and antecedent geology. Depending
on the relative dominance of wave and tide forcing,
coastal environments can be classified as tide-dominated
and wave-dominated (Davis and Hayes
1984
). This
chapter focuses on general physical processes of sedi-
ment transport that are applicable to the tide-dominated
environments. In this chapter, tidal environments are
defined generally as shallow marine environments that
are significantly influenced by tides.
The rise and fall of tides provide the main mecha-
nism for sediment transport and morphology changes
in tidal environments. In addition to generating tidal
current which constitutes the dominant forcing in tidal
environments, this regulated water-level fluctuation
can also modulate wave action. For example, higher
u
(
z
):
current velocity with respect to depth
z
(m/s)
u
:
depth-averaged current velocity (m/s)
u
*
:
current related bed-shear velocity (m/s)
u
*_c
:
critical bed shear velocity (m/s)
u
*_crs
:
critical shear velocity for sediment suspension
(m/s)
u
:
depth-averaged critical velocity (m/s)
cr
v
:
depth average velocity in
y
direction (m/s)
w
s
:
settling velocity (m/s)
w
s_s
:
settling velocity of single suspended particle
in clear water used in the calculation of the
settling velocity of flocs (m/s)
z
:
vertical coordinate representing water depth (m)
z
o
:
vertical level with zero velocity, also often
referred to as bed roughness (m)
D
1
:
empirical coefficients used in suspended sedi-
ment concentration profile modeling (dimen-
sionless)
