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Coastal Engineering: Theory and Practice
Seawalls and bulkheads
A seawall is a structure constructed parallel to the coastline that shelters
the shore from wave action. It is both massive and expensive. Erection
of sea wall shall be considered only after carefully evaluating the socioeconomic parameters, i.e. it is recommended to construct a seawall when
the adjoining shore is highly developed and the intensity of storm attack
is severe. It is an irréversible process where the beach area in front of the
structure is permanently lost. Seawalls are broadly classified as rigid, flexible and composite type. Rigid seawalls are the structures generally most
of its seaward side face being vertical, sloping or curved and are imperméable. These seawalls are usually constructed as monolithic gravity structures consisting of a concrète caisson filled with sand. It provides complété
protection for the shore from the destructive action of océan waves, and is
provided with a toe protection to prevent toe scouring. The flexible seawalls are permeable rubble mound structures armoured with natural rocks
or artificial armour units or gabions. The dissipation of the incident wave
energy in the presence of these structures is mainly due to wave breaking
on the slope. Réhabilitation of the lost armour layer units is mandatory for
longevity of the structures. Composite seawalls are a combination of rubble
mound seawall with a crown of rigid imperméable wall (either vertical or
curved), wherein, the crown wall rests on the mound of stones, relying on
its mass to resist the wave action. This type is adopted at locations, where,
the foundation soil is poor and a high tidal variation pertains. During low
tide, the structure will act as rubble mound (permeable type) and during
high tide it acts as imperméable wall type, with less force on the rigid
imperméable wall due to the presence of rubble mound toe in front. Some
spécial types of seawalls are also being constructed using gabion mattress
and geotubes filled with sand. The different types of seawalls as discussed
are illustrated in Fig. 4.6. A bulkhead is very much similar to a seawall
except for its primary purpose which is to prevent sliding of land mass,
whereas, a seawall’s primary purpose is to protect backshore against wave
action.
Groins
A groin is a shore connected structure constructed perpendicular to the
coastline and jetting into the sea which serve as barrier in trapping the
longshore sédiment transport or control longshore currents. Different plan
Coastal Engineering: Theory and Practice
Seawalls and bulkheads
A seawall is a structure constructed parallel to the coastline that shelters
the shore from wave action. It is both massive and expensive. Erection
of sea wall shall be considered only after carefully evaluating the socioeconomic parameters, i.e. it is recommended to construct a seawall when
the adjoining shore is highly developed and the intensity of storm attack
is severe. It is an irréversible process where the beach area in front of the
structure is permanently lost. Seawalls are broadly classified as rigid, flexible and composite type. Rigid seawalls are the structures generally most
of its seaward side face being vertical, sloping or curved and are imperméable. These seawalls are usually constructed as monolithic gravity structures consisting of a concrète caisson filled with sand. It provides complété
protection for the shore from the destructive action of océan waves, and is
provided with a toe protection to prevent toe scouring. The flexible seawalls are permeable rubble mound structures armoured with natural rocks
or artificial armour units or gabions. The dissipation of the incident wave
energy in the presence of these structures is mainly due to wave breaking
on the slope. Réhabilitation of the lost armour layer units is mandatory for
longevity of the structures. Composite seawalls are a combination of rubble
mound seawall with a crown of rigid imperméable wall (either vertical or
curved), wherein, the crown wall rests on the mound of stones, relying on
its mass to resist the wave action. This type is adopted at locations, where,
the foundation soil is poor and a high tidal variation pertains. During low
tide, the structure will act as rubble mound (permeable type) and during
high tide it acts as imperméable wall type, with less force on the rigid
imperméable wall due to the presence of rubble mound toe in front. Some
spécial types of seawalls are also being constructed using gabion mattress
and geotubes filled with sand. The different types of seawalls as discussed
are illustrated in Fig. 4.6. A bulkhead is very much similar to a seawall
except for its primary purpose which is to prevent sliding of land mass,
whereas, a seawall’s primary purpose is to protect backshore against wave
action.
Groins
A groin is a shore connected structure constructed perpendicular to the
coastline and jetting into the sea which serve as barrier in trapping the
longshore sédiment transport or control longshore currents. Different plan