the coast 1. the sea 2 wind waves the sea 3 tidescurrents 1.long-shore 2.cross-shore
TRANSCRIPT
1
The Coast
2
The Sea
Wind Waves
3
The Sea
Tides Currents1. Long-Shore 2. Cross-Shore
4
The Sea
Currents
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Shore protection structures
GroinsA groin is a shore protection
structure designed to
build a protective beach
or to retard erosion of an
existing beach by
trapping littoral drift
Groins are usually
perpendicular to the
shore and extend from a
point landward into the
water far enough to
accomplish their
purpose
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Shore protection structures
The effect of groins on the coastGroins interrupt the longshore transport. As a result accretion occurs
at the updrift side and erosion at the downdrift side
The re-orientation of the shoreline between the groins results in local
retreat of the shoreline relative to the original position. This can be
restored by applying some sand nourishment between the groins.
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Shore protection structures
GroinsA system of groins may be an effective coastal protection scheme, and it can be considered as a proven technology for which the effects on the coast can be reasonably well predicted.
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Shore protection structures
JettiesJetties are structures used at
inlets to stabilize the
position of the
navigation channel, to
shield vessels from
wave forces, and to
control the movement of
sand along the adjacent
beaches so as to
minimize the movement
of sand into the channel.
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Shore protection structures
Jetties
The sand transport into an inlet
will interfere with navigation and
will usually necessitate more
frequent dredging to maintain the
navigation depth.
Because of the longshore
transport reversals common at
many sites, jetties are often
required on both sides of the inlet
to achieve complete channel
protection
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Shore protection structures
Breakwaters1. Shore Connected2. Offshore
Shore Connected BreakwatersShore connected breakwaters are used to shelter commercial harbors and small craft marinas by creating calm water in a harbor area, and provide protection for safe mooring, operating and handling of ships, and for harbor facilities
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Shore protection structures
Breakwaters1. Shore Connected2. Offshore
Offshore BreakwatersAn offshore breakwater is a structure that is designed to provide protection from wave action to an area or shoreline located on the leeward side of the structure.
This system is usually built approximately parallel to the shore or to the predominant wave train.
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Shore protection structures
Offshore BreakwatersDetached Breakwaters have many advantages over other conventional forms of shore protection.
Unlike groins, they allow sand to be transported alongshore, protecting the local beach, but not depriving downdrift beaches of sand.
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Shore protection structuresNourishment (Beach fill)Beach fill is a traditional and increasingly popular method of shore protection and flood control, and nourished beaches also have value for recreational, commercial, and environmental purposes.
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Shore protection structuresNourishment (Beach fill)
Nourishment is a process of feeding a beach periodically with the amount of sand that was lost during this period. Fill is commonly placed together with the building of coastal structures such as groin fields and detached breakwaters
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Shore protection structuresNourishment (Beach fill)When the natural protection system fails during large storms, the first solutions frequently chosen are quasi-natural methods such as beach nourishment or artificial sand-dune building.
Such solutions retain the beach as a very effective wave energy dissipater and the dune as a flexible last line of defense.
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Shore protection structures
Seawalls and RevetmentsSeawalls and revetments are structures placed parallel or nearly parallel to the shoreline to separate a land area from a water area.
They do not attract the sand or prevent longshore transport, but they only hinder the transport and protect the backshore.
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Shore protection structures
Seawalls and RevetmentsSeawalls are simply retaining the beach material behind them, so they can be assumed as a retaining wall that should be maintained stable.
They can be built so high that no water would overtop the crest of the structure and wing walls must be designed to prevent progressive failure that may be found at the ends of the structure
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Shore protection structures
Seawalls and Revetments
If they are permeable, they absorb part of the energy of the incoming waves and reflect the other part back to the sea.