of the finer sizes of sand. Daytona Beach, Florida, is a good example
of a gently sloping beach composed of fine sand.
1.43 BREAKERS
As a wave moves toward shore, it reaches a depth of water so shallow
that the wave collapses or breaks. This depth is equal to about 1.3 times
the wave height. Thus a wave 3 feet high will break in a depth of about
4 feet. Breaking can occur in several different ways (plunging, spilling,
surging, or collapsing). Breaking results in a dissipation of the energy
of the wave and is manifested by turbulence in the water. This turbulence
stirs up the bottom materials. For most waves, the water travels forward
after breaking as a foaming, turbulent mass, expending most of its remaining energy in a rush up the beach slope.
1.44 EFFECTS OF WIND WAVES
Wind waves affect beaches in two major ways. Short steep waves,
which usually occur during a storm near the coast, tend to tear the
beach down. (See Figure 1-7.) Long swells, which originate from distant storms, tend to rebuild the beaches. On most beaches, there is a
constant change caused by the tearing away of the beach by local storms
followed by graduai rebuilding by swells. A sériés of violent local
storms in a short time can resuit in severe érosion of the shore if
there is not enough time between storms for swells to rebuild the
beaches. Altemate érosion and accretion of beaches may be seasonal
on some beaches; the winter storms tear the beach away, and the summer
swells rebuild it. Beaches may also follow long-term cyclic patterns.
They may erode for several years, and then accrete for several years.
1.45 LITTORAL TRANSPORT
Littoral transport is defined as the movement of sédiments in the
nearshore zone by waves and currents and is divided into two general
classes: transport parallel to the shore (longshore transport) and
transport perpendicular to the shore (onshore-offshore transport). This
transport is distinguished from the material moved, which is called
littoral drift.
Onshore-offshore transport is determined primarily by wave steepness,
sédiment size, and beach slope. In general, high steep waves move material
offshore, and low waves of long period (low steepness waves) move material
onshore. This onshore-offshore process associated with storm waves is
illustrated in Figure 1-7.
Longshore transport results from the stirring up of sédiment by the
rea ing wave, and the movement of this sédiment by the component of the
wave m an alongshore direction, and by the longshore current generated
y the breaking wave. The direction of longshore transport is directly
reiatecl to the direction of wave approach, and the angle of the wave to
the shore. Thus, due to the variability of wave approach, longshore
of a gently sloping beach composed of fine sand.
1.43 BREAKERS
As a wave moves toward shore, it reaches a depth of water so shallow
that the wave collapses or breaks. This depth is equal to about 1.3 times
the wave height. Thus a wave 3 feet high will break in a depth of about
4 feet. Breaking can occur in several different ways (plunging, spilling,
surging, or collapsing). Breaking results in a dissipation of the energy
of the wave and is manifested by turbulence in the water. This turbulence
stirs up the bottom materials. For most waves, the water travels forward
after breaking as a foaming, turbulent mass, expending most of its remaining energy in a rush up the beach slope.
1.44 EFFECTS OF WIND WAVES
Wind waves affect beaches in two major ways. Short steep waves,
which usually occur during a storm near the coast, tend to tear the
beach down. (See Figure 1-7.) Long swells, which originate from distant storms, tend to rebuild the beaches. On most beaches, there is a
constant change caused by the tearing away of the beach by local storms
followed by graduai rebuilding by swells. A sériés of violent local
storms in a short time can resuit in severe érosion of the shore if
there is not enough time between storms for swells to rebuild the
beaches. Altemate érosion and accretion of beaches may be seasonal
on some beaches; the winter storms tear the beach away, and the summer
swells rebuild it. Beaches may also follow long-term cyclic patterns.
They may erode for several years, and then accrete for several years.
1.45 LITTORAL TRANSPORT
Littoral transport is defined as the movement of sédiments in the
nearshore zone by waves and currents and is divided into two general
classes: transport parallel to the shore (longshore transport) and
transport perpendicular to the shore (onshore-offshore transport). This
transport is distinguished from the material moved, which is called
littoral drift.
Onshore-offshore transport is determined primarily by wave steepness,
sédiment size, and beach slope. In general, high steep waves move material
offshore, and low waves of long period (low steepness waves) move material
onshore. This onshore-offshore process associated with storm waves is
illustrated in Figure 1-7.
Longshore transport results from the stirring up of sédiment by the
rea ing wave, and the movement of this sédiment by the component of the
wave m an alongshore direction, and by the longshore current generated
y the breaking wave. The direction of longshore transport is directly
reiatecl to the direction of wave approach, and the angle of the wave to
the shore. Thus, due to the variability of wave approach, longshore