problems involving littoral processes would not occur. A knowledge of
incident waves, or of surf, is essential for Coastal engineering planning,
design, and construction.
Three important aspects of a study of waves on beaches are: the
theoretical description of wave motion; the climatological data for waves
as they occur on a given segment of coast ; and the description of how
waves interact with the shore to move sand.
The theoretical approach can provide a useful description of water
motion caused by waves when the limiting assumptions of the theory are
satisfied. Surprisingly, the small-amplitude theory (Section 2.23) and
aspects of solitary wave theory (Section 2.27) hâve proved useful beyond
the limits assumed in their dérivations.
The theoretical description of water-wave motion provides estimâtes
of water motion, longshore force, and energy flux due to waves. These
estimâtes are useful in understanding the effect of waves on sédiment
transport, but currently (1973) the prédiction of wave-induced sédiment
motion for engineering purposes relies heavily on empirical coefficients
and judgement rather than on theory.
Statistical distributions of wave characteristics along a given shoreline provide a basis for describing the wave climate of a Coastal segment.
Important wave characteristics affecting sédiment transport near the beach
are height, period, and direction of breaking waves. Breaker height is
significant in determining the quantity of sand in motion; breaker direction is a major factor in determining longshore transport direction and
rate. Waves affect sédiment motion in the littoral zone in two ways:
they initiate sédiment movement, and they drive current Systems that transport the sédiment once motion is initiated.
4.122 Currents. Water waves induce an orbital motion in the fluid beneath
(See Section 2.23.) These are not closed orbits, and the fluid
expériences a slight wave-induced drift, or mass transport. Magnitude and
direction of mass transport are functions of élévation above bottom and
wave parameters (Equation 2-55) , and are also influenced by wind and température gradients. The action of mass transport, extended over a long
period, can be important in carrying sédiment onshore or offshore, particularly seaward of the breaker position.
As waves approach breaking, wave-induced bottom motion in the water
cornes more intense, and its effect on sédiment becomes more pronounced.
reaking waves create intense local currents (turbulence) that move sedimntinn iî
cro?s the surf zone after breaking, the accompanying fluid
ç
s y uniform horizontal motion, except during the brief passage o the breaker front where significant turbulence occurs. Since wave
■" ‘Ln bre*kln8 are usuallx at a slight angle to the shoreline, there
breakino wavAc°n^Tv°re,COnlP?nent of ">omentum in the fluid composing the
g
es. This longshore component of momentum entering the surf
4-4
incident waves, or of surf, is essential for Coastal engineering planning,
design, and construction.
Three important aspects of a study of waves on beaches are: the
theoretical description of wave motion; the climatological data for waves
as they occur on a given segment of coast ; and the description of how
waves interact with the shore to move sand.
The theoretical approach can provide a useful description of water
motion caused by waves when the limiting assumptions of the theory are
satisfied. Surprisingly, the small-amplitude theory (Section 2.23) and
aspects of solitary wave theory (Section 2.27) hâve proved useful beyond
the limits assumed in their dérivations.
The theoretical description of water-wave motion provides estimâtes
of water motion, longshore force, and energy flux due to waves. These
estimâtes are useful in understanding the effect of waves on sédiment
transport, but currently (1973) the prédiction of wave-induced sédiment
motion for engineering purposes relies heavily on empirical coefficients
and judgement rather than on theory.
Statistical distributions of wave characteristics along a given shoreline provide a basis for describing the wave climate of a Coastal segment.
Important wave characteristics affecting sédiment transport near the beach
are height, period, and direction of breaking waves. Breaker height is
significant in determining the quantity of sand in motion; breaker direction is a major factor in determining longshore transport direction and
rate. Waves affect sédiment motion in the littoral zone in two ways:
they initiate sédiment movement, and they drive current Systems that transport the sédiment once motion is initiated.
4.122 Currents. Water waves induce an orbital motion in the fluid beneath
(See Section 2.23.) These are not closed orbits, and the fluid
expériences a slight wave-induced drift, or mass transport. Magnitude and
direction of mass transport are functions of élévation above bottom and
wave parameters (Equation 2-55) , and are also influenced by wind and température gradients. The action of mass transport, extended over a long
period, can be important in carrying sédiment onshore or offshore, particularly seaward of the breaker position.
As waves approach breaking, wave-induced bottom motion in the water
cornes more intense, and its effect on sédiment becomes more pronounced.
reaking waves create intense local currents (turbulence) that move sedimntinn iî
cro?s the surf zone after breaking, the accompanying fluid
ç
s y uniform horizontal motion, except during the brief passage o the breaker front where significant turbulence occurs. Since wave
■" ‘Ln bre*kln8 are usuallx at a slight angle to the shoreline, there
breakino wavAc°n^Tv°re,COnlP?nent of ">omentum in the fluid composing the
g
es. This longshore component of momentum entering the surf
4-4