Geoscience Reference
In-Depth Information
TABLE 6.5
Morphometric Parameters
Parameter
Description
Restriction ratio, defined as the ratio between the total width of the
lagoon entrances and the along-shore length,
.
Orientation or anisotrophy parameter. The lagoon has orthogonal
dimensions of the same order if . It is more elongated in the
parallel or perpendicular to shore directions if or ,
respectively. In case of difficulties in explicit determination of cross-
shore lagoon size (for example, the lagoon consists of series of
connected elliptical cells), the transversal dimension together with
lagoon surface area (
S
lag
) may be used for estimation of this parameter.
Shallowness parameter, the range that characterizes the lagoon
shallowness as a whole. This parameter is the inverse of the width-
to-depth ratio usually applied to estuary classification.
4
Extreme depth parameter, which provides information on the deepest
part of the lagoon and how it compares to the mean depth.
d
b
=
∑
d
b
p
=
,
p
i
p
r
∈(,)
01
r
r
b
a
p
=
p
or
≈ 1
or
p
or
≥ 1
p
or
≤ 1
S
a
b
S
2
lag
p
=
=
or
2
lag
max( ,
h
h
avg
avg
p
∈
)
,
shall
ab
min( ,
ab
)
p
=
h
max
/
h
deep
avg
Openness parameter, which characterizes the potential influence of
the sea on lagoon general hydrology because flow velocities through
the entrances are not included. Here,
in
=
∑
s
p
i
,
open
S
lag
s
i
in
is the cross-sectional area
of
i
th lagoon entrance for
i
=
1,
n
entrances, and
S
lag
is the area of
the lagoon surface.
A three-component parameter of flow, which illustrates the hydraulic
resistance of the lagoon in different respects. Here,
s
max
and
s
min
are
the maximum and minimum cross-sectional areas, respectively
inside the lagoon and
s
inlet
is the minimal cross-sectional area at the
inlet. This set of components is valuable for pre-estimation of
hydraulic resistance inside the lagoon.
Network parameter that characterizes the “length” of the channel
network structure. Here,
L
km
is the length of the link between nodes
k
and
m
.
Parameter that characterizes the “density” of the channel network
structure. Here,
L
km
and
D
km
are the length and width of the link
between nodes
k
and
m
.
∈
s
s
s
s
s
s
!
"
p
max
min
,
max
,
min
resist
inlet
inlet
max( ,
∑
L
ab
∑
L
ab
p
∈
km
)
,
km
net
min( ,
)
=
∑⋅
⋅
LD
ab
p
km
km
dens
Branching parameters for channel network structures.
L
min
and
L
max
are the minimum and maximum lengths of links between two remote
marginal entrances. This parameter characterizes the “multi-
variability” of ways through the lagoon system.
Sediment structure parameter that characterizes the average diameter
of sediment in the lagoon. It can be estimated as the spatial average
between the diameters (
d
i
) of different sediment occupying the areas
(
S
i
) in the lagoon.
p
=
L
∑
L
km
,
short
min
p
=
L
max
/
∑
L
km
long
S
S
p
=∑ ⋅
d
i
sed
i
lag
p
shore
=
l⋅(4⋅π ⋅A)
−0.5
,
Shore development parameter, which is the ratio of the length of
lagoon shore line (
l
) to the circumference of a circle whose area A
is equivalent to that of the lagoon.
Parameters that illustrate what fraction of the total lagoon coast line is
under erosion (
p
,
p
,
p
err
acr
eq
p
err
), accretion (
p
acr
), or equilibrium (
p
eq
) conditions,
and which are normalized as follows:
p
++
p
p
1.
err
acr
eq
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