3. Sédiment Transport
57
approaching to shore at an angle (et) are the primary cause for longshore
sédiment transport. Waves approaching perpendicular to the shore responsible for cross-shore sédiment transport and oblique wave responsible for
longshore sédiment transport are brought out in Fig. 3.13.
P
.
w Pcosa
Fig. 3.13 Wave direction normal to the shore and at an angle (a) to the shore.
Where P is the wave power, given as,
P = ECg = (l/8)pgH2Cg
(3.23)
As the alongshore wave power component breaks into two components,
it can be re written as
Alongshore = P cos a • cos(90 — et) = P cos a • sin a
Hence, the wave crests make an angle, a with the shoreline, the energy
flux becomes,
P cos a = ^H2Cg cos a
(3.24)
8
a = angle between wave direction and shore normal and the longshore
component is given by
Pis = F cos et sin et = ^-H2Cg cos et sin et,
Pis = ^H2Cg sin 2a,
8
10
(since, sin 2q = 2 • cos a • sin et)
(3.25)
Based on the approximation at breaker line, the équation can be
written as,
fl, = ^HÎCbsm1ab
(3.26)
The above équation is valid only if there is a single wave train with one
period and one height. However, most océan wave conditions are characterized by a variety of heights with a distribution usually described by a
Rayleigh distribution. For a Rayleigh distribution, the correct height to use
in above équation is the root-mean-square height. Whereas, most wave data
57
approaching to shore at an angle (et) are the primary cause for longshore
sédiment transport. Waves approaching perpendicular to the shore responsible for cross-shore sédiment transport and oblique wave responsible for
longshore sédiment transport are brought out in Fig. 3.13.
P
.
w Pcosa
Fig. 3.13 Wave direction normal to the shore and at an angle (a) to the shore.
Where P is the wave power, given as,
P = ECg = (l/8)pgH2Cg
(3.23)
As the alongshore wave power component breaks into two components,
it can be re written as
Alongshore = P cos a • cos(90 — et) = P cos a • sin a
Hence, the wave crests make an angle, a with the shoreline, the energy
flux becomes,
P cos a = ^H2Cg cos a
(3.24)
8
a = angle between wave direction and shore normal and the longshore
component is given by
Pis = F cos et sin et = ^-H2Cg cos et sin et,
Pis = ^H2Cg sin 2a,
8
10
(since, sin 2q = 2 • cos a • sin et)
(3.25)
Based on the approximation at breaker line, the équation can be
written as,
fl, = ^HÎCbsm1ab
(3.26)
The above équation is valid only if there is a single wave train with one
period and one height. However, most océan wave conditions are characterized by a variety of heights with a distribution usually described by a
Rayleigh distribution. For a Rayleigh distribution, the correct height to use
in above équation is the root-mean-square height. Whereas, most wave data