]II. Sediment Transport ............
131
~N~vq er'Qtt
..._...--'"T"
=
• S o,
....
x
Fig. 29 : Longshore sediment transport
When defining :
Oy
dS t
ot ~.tanot -
and ~
=S 1
Ox
dot
Equation (72) yields :
Oy
Sl(ot) =Sol -s I -Ox
where :
S~ (ot)
Sol
Sl
ot
(73)
(74)
= longshore transport as a function of the coastline direction
= longshore transport along a straight parallel to the x-axis
= variation of the longshore transport per radian of the coastline rotation
= coastline direction with respect to the x-axis in radians
Eq. (74) is the Pelnard-Consid6re equation wherein the coastal constant Sol and
sl may be functions of x. When the equation of motion (74) is substituted in the
equation of continuity (70) the following relation is obtained (with constant Sol
and sl, and p = 0) :
Oy s I t9 2y
-
(75)
0t
h 0x 2
This is the so-called equation of diffusion for which analytical solutions can be
found.