298
with Qi* = bi qi and Qi = ki Qg
R.H. Charlier and Chr. P. De Meyer
meaning that the difference of all credits to all debits is nil. Any deviation from 0
indicates an estimated rate of erosion or accretion. Symbols used in 0IL 1) are
identified below.
Q
are credits (+) or debits (o) a.k.a, source and sink points, Q* being a plus (+)
or minus total contribution of a budget line calculated over the distance
involved (mVy).
q
are source (+) or sink (-) lines, viz. adding or subtracting over an extended
segment of a control volume boundary (mVy/km).
b
is the length of the shoreline segment of activity
k
is the fraction of the gross longshore transport rate (Qg).
i
(= 1, 2, 3 or 4) identifies the location of source or sink ("where" in littoral
zone).
In regards to Qg, it is the sum of amounts transported to right (Qrt) and left Q(lt)
of a given point.on the shoreline during a unit of time. The difference between
these amounts is the net (Qn) transport rate. Qrt and Qlt are used in design of
jetties and impoundment basins, Qn for prediction of beach erosion on an open
coast. When only a ratio (3') is known, Qg and Qn are related by (III.5). When 3'
--, _1, equation (111.5) --, and is of no use.
Thus, summarizing.
O~ =
Qrt + Qlt
(III.2)
Q,,=
Qa - Qlt
(III.3)
3, =
Q~t/Q~t
(III.4)
Qg=
Q.(I+ ,),)
(III.5)
(I-v)
Another representation of the longshore transport rate can be given by the
immersed weight rate I 1 (force unit/time unit, p.ex.. With Ps as the mass density
of sand (sediment), p the mass density of water, a' the volume of solids/total
volume (to account for porosity),
I1 = (as - P) g a' Q
(111.6)
with Qi* = bi qi and Qi = ki Qg
R.H. Charlier and Chr. P. De Meyer
meaning that the difference of all credits to all debits is nil. Any deviation from 0
indicates an estimated rate of erosion or accretion. Symbols used in 0IL 1) are
identified below.
Q
are credits (+) or debits (o) a.k.a, source and sink points, Q* being a plus (+)
or minus total contribution of a budget line calculated over the distance
involved (mVy).
q
are source (+) or sink (-) lines, viz. adding or subtracting over an extended
segment of a control volume boundary (mVy/km).
b
is the length of the shoreline segment of activity
k
is the fraction of the gross longshore transport rate (Qg).
i
(= 1, 2, 3 or 4) identifies the location of source or sink ("where" in littoral
zone).
In regards to Qg, it is the sum of amounts transported to right (Qrt) and left Q(lt)
of a given point.on the shoreline during a unit of time. The difference between
these amounts is the net (Qn) transport rate. Qrt and Qlt are used in design of
jetties and impoundment basins, Qn for prediction of beach erosion on an open
coast. When only a ratio (3') is known, Qg and Qn are related by (III.5). When 3'
--, _1, equation (111.5) --, and is of no use.
Thus, summarizing.
O~ =
Qrt + Qlt
(III.2)
Q,,=
Qa - Qlt
(III.3)
3, =
Q~t/Q~t
(III.4)
Qg=
Q.(I+ ,),)
(III.5)
(I-v)
Another representation of the longshore transport rate can be given by the
immersed weight rate I 1 (force unit/time unit, p.ex.. With Ps as the mass density
of sand (sediment), p the mass density of water, a' the volume of solids/total
volume (to account for porosity),
I1 = (as - P) g a' Q
(111.6)