and marshes then outcrop along the shore. (e.g. Kraft, 1971.) Many barrier
islands along the Atlantic and Gulf coasts contain tidal and marsh deposits
at or near the surface of the littoral zone. The fine material is often
bound together by the roots of marsh plants to form a cohesive déposât
that may function for a time as beach protection.
4.24 CONSOLIDATED MATERIAL
Along some coasts, the principal littoral materials are Consolidated
materials, such as rock, beach rock, and coral, rather than unconsolidated
sand. Such Consolidated materials protect a coast and resist shoreline
changes.
4.241 Rock. Exposed rock along a shore indicates that the rate at which
sand is supplied to the coast is less than the potential rate of sand
transport by waves and currents. Reaction of a rocky shore to wave attack
is determined by the structure, degree of lithification, and ground water
characteristics of the exposed rock, and by the severity of the wave
climate. Protection of eroding cliffs is a complex problem involving
geology, rock mechanics, and Coastal engineering. Two examples of these
problems are the protection of the cliffs at Newport, Rhode Island (U. S.
Army, Corps of Engineers, 1965) and at Gay Head, Martha’s Vineyard,
Massachusetts. (U.S. Army, Corps of Engineers, 1970.)
Most rocky shorelines are remarkably stable, with individual rock
masses identified in photos taken 50 years apart. (Shepard and Grant,
1947.)
4.242 Beach Rock. A layer of friable to well-lithified rock often occurs
at or near the surface of beaches in tropical and subtropical climates.
This material consists of local beach sédiment cemented with calcium carbonate, and it is commonly known as beach rock. Beach rock is important
to Coastal engineers because it provides added protection to the coast,
greatly reducing the magnitude of beach changes (Tanner, 1960), an
e
cause beach rock may affect construction activities. (Gonzales, iy/u.j
,
w -rnrk is formed when saline waters
According to Bricker (1971), beac
carbonate from solution. The
evaporate in beach sands, depositmg ca
i;mited to tropical coasts, such
présent active formation of beach roc i
. |s cominon at shallow
as the Florida Keys, but rock resemblmg
Louisiana beaches, and redepths along the east coast of Flori a,
as t^e prazer River Delta
lated deposits hâve been reported as a
subiect is given in Bricker
in Canada. Comprehensive discussion of the sudj
(1971) and Russell (1970).
far north as the Frazer River Delta
. Organic reefs are wave-resistant structures reacha level that hâve been formed by calcium carbonate
- ’
-.jj--- cme are herma4.243 Organic Reefs. Organic ree s
_______ ,
ing to about mean sea levei tnat navc u
organisms are
secreting organisms. The most co
forming corals are usua y
typic corals and coralline algae.
tures above about 18 C ( epa ,
stricted to areas having winter teŒP
wider range. On U.S.
1963, p. 351), but coralline algae h
4-21
islands along the Atlantic and Gulf coasts contain tidal and marsh deposits
at or near the surface of the littoral zone. The fine material is often
bound together by the roots of marsh plants to form a cohesive déposât
that may function for a time as beach protection.
4.24 CONSOLIDATED MATERIAL
Along some coasts, the principal littoral materials are Consolidated
materials, such as rock, beach rock, and coral, rather than unconsolidated
sand. Such Consolidated materials protect a coast and resist shoreline
changes.
4.241 Rock. Exposed rock along a shore indicates that the rate at which
sand is supplied to the coast is less than the potential rate of sand
transport by waves and currents. Reaction of a rocky shore to wave attack
is determined by the structure, degree of lithification, and ground water
characteristics of the exposed rock, and by the severity of the wave
climate. Protection of eroding cliffs is a complex problem involving
geology, rock mechanics, and Coastal engineering. Two examples of these
problems are the protection of the cliffs at Newport, Rhode Island (U. S.
Army, Corps of Engineers, 1965) and at Gay Head, Martha’s Vineyard,
Massachusetts. (U.S. Army, Corps of Engineers, 1970.)
Most rocky shorelines are remarkably stable, with individual rock
masses identified in photos taken 50 years apart. (Shepard and Grant,
1947.)
4.242 Beach Rock. A layer of friable to well-lithified rock often occurs
at or near the surface of beaches in tropical and subtropical climates.
This material consists of local beach sédiment cemented with calcium carbonate, and it is commonly known as beach rock. Beach rock is important
to Coastal engineers because it provides added protection to the coast,
greatly reducing the magnitude of beach changes (Tanner, 1960), an
e
cause beach rock may affect construction activities. (Gonzales, iy/u.j
,
w -rnrk is formed when saline waters
According to Bricker (1971), beac
carbonate from solution. The
evaporate in beach sands, depositmg ca
i;mited to tropical coasts, such
présent active formation of beach roc i
. |s cominon at shallow
as the Florida Keys, but rock resemblmg
Louisiana beaches, and redepths along the east coast of Flori a,
as t^e prazer River Delta
lated deposits hâve been reported as a
subiect is given in Bricker
in Canada. Comprehensive discussion of the sudj
(1971) and Russell (1970).
far north as the Frazer River Delta
. Organic reefs are wave-resistant structures reacha level that hâve been formed by calcium carbonate
- ’
-.jj--- cme are herma4.243 Organic Reefs. Organic ree s
_______ ,
ing to about mean sea levei tnat navc u
organisms are
secreting organisms. The most co
forming corals are usua y
typic corals and coralline algae.
tures above about 18 C ( epa ,
stricted to areas having winter teŒP
wider range. On U.S.
1963, p. 351), but coralline algae h
4-21