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Offshore
zone
Nearshore zone
or shoreface
Backshore
zone
Swash
zone
Sand
dune
Surf zone
Breaker zone
Foredune
Berm
HWM
Tidal
range
MSL
LWM
Bar
Beachface
Intertidal
zone
Fig. 8.8 Nearshore wave zones and profile morphology: HWM, high water mark; LWM, low water mark; MSL, mean sea level. In the
offshore zone waves begin to interact with the sea-bed, and increase in height as the water depth diminishes. Waves break, generating
bars as they do so, in the breaker zone and propagate across the surf zone toward the shoreline. The final wave energy dissipation occurs
in the swash zone. Overwashing occurs when waves overtop the berm and flow landward across the backshore. Aeolian transport of
sand from the beach may produce dunes at the rear of the beach.
in water level, often observed as regularly spaced,
alongshore peaks in swash. In addition, second-
ary currents may be generated due to inequalities
in the water surface elevation and energy density.
These currents may be arranged into circulatory
cells that redistribute water through shore-
normal (rip) and/or shore-parallel (longshore)
currents (Fig. 8.9).
Energy that propagates to the shore through
the surf zone to the beach may run up the beach
for some distance as swash. The elevation to
which swash rises is dependent on wave height,
the porosity of the beach material and the extent
of saturation at any given time. Excess water
that does not infiltrate the beach runs back
down the beach as backwash. The high porosity
of gravel beaches reduces or eliminates back-
wash. Swash is normally the zone in which
final dissipation of wave energy takes place. On
steep beaches, however, excess energy may be
reflected seaward, or, if the swash reaches the
beach berm, it may flow in a landward direction
as overwash.
Waves are thus responsible for a variety of fluid
motions and potential sediment-transporting
mechanisms on temperate coasts. Commonly,
for ease of understanding these are divided into
cross-shore and longshore transport mechan-
isms, although in reality the system is fully
(a)
Beach
Breaker zone
Rip
current
Rip
current
Return
Wave crest
Beach
(b)
Longshore current
(c)
Beach
Reflection
Reflection
Edge
wave
Fig. 8.9 Nearshore circulations in the surf zone take the form of
circulation systems (a) comprising rip currents and alongshore
currents, (b) shore currents generated by oblique incident waves
and (c) edge waves produced by reflection of incident wave
energy from steep beaches and subsequent refraction back
towards the shoreline.
 
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