than are typical of Atlantic coast beaches. (Urban and Gai vin, 1969;
Zeigler and Tuttle, 1961.) Available data indicate that the greatest
changes on the profile are in the position of the beach face and of the
longshore bar - two relatively mobile éléments of the profile. Beaches
change in plan view as well. Figure 4-6 shows the change in shoreline
position at seven east coast localities as a function of time between
autumn 1962 and spring 1967.
Comparison of beach profiles before and after storms suggests érosion of the beach above MSL from 10,000 to 50,000 cubic yards per mile
of shoreline during storms expected to recur about once a year. (DeWall,
et al., 1971; and Shuyskiy, 1970.) While impressive in aggregate, such*
sédiment transport is minor compared to longshore transport of sédiment.
Longshore transport rates may be greater than 1 million cubic yards per
year.
The long-term changes shown in Figures 4-3, 4-4, and 4-5 illustrate
shorelines of érosion, accretion, and stability. Long-term érosion or
accretion rates are rarely more than a few feet per year in horizontal
motion of the shoreline, except in localities particularly exposed to
érosion, such as near inlets or capes. Figure 4-5 indicates that shorelines can be stable for a long time. It should be noted that the eroding, accreting, and stable beaches shown in Figures 4-3, 4-4, and 4-5
are on the same barrier island within a few miles of each other.
Net longshore transport rates along océan beaches range from near
zéro to 1 million cubic yards per year, but are typically 100,000 to
500,000 cubic yards per year. Such quantifies, if removed from a 10- to
20-mile stretch of beach year after year, would resuit in severe érosion
problems. The fact that many beaches hâve high rates of longshore transport without unusually severe érosion suggests that an equilibrium condi
tion exists on these beaches, in which the material eroded is balanced by
the material supplied; or in which seasonal reversais of littoral transport replace material previously removed.
4-2 LITTORAL MATERIALS
Littoral materials are the solid materials (mainly sedimentary)
the littoral zone on which the waves and currents act.
4«21 CLASSIFICATION
The characteristics of the littoral materials are a Pr^^sfifreto any Coastal engineering design. Médian grain size
Quently used design characteristic.
4,211 Size
Size Parameters. Littoral m^®rial'da^uid^lfse^eral
^ain size into clay, silt, sand, gravel, cob
Classification
size classifications exist, of which two, t e^^i^ie^^ Classification
( ased on the Casagrande Classification) an
Pipure 4-7.) The
are most commonly used in Coastal engineering.
4-H
Zeigler and Tuttle, 1961.) Available data indicate that the greatest
changes on the profile are in the position of the beach face and of the
longshore bar - two relatively mobile éléments of the profile. Beaches
change in plan view as well. Figure 4-6 shows the change in shoreline
position at seven east coast localities as a function of time between
autumn 1962 and spring 1967.
Comparison of beach profiles before and after storms suggests érosion of the beach above MSL from 10,000 to 50,000 cubic yards per mile
of shoreline during storms expected to recur about once a year. (DeWall,
et al., 1971; and Shuyskiy, 1970.) While impressive in aggregate, such*
sédiment transport is minor compared to longshore transport of sédiment.
Longshore transport rates may be greater than 1 million cubic yards per
year.
The long-term changes shown in Figures 4-3, 4-4, and 4-5 illustrate
shorelines of érosion, accretion, and stability. Long-term érosion or
accretion rates are rarely more than a few feet per year in horizontal
motion of the shoreline, except in localities particularly exposed to
érosion, such as near inlets or capes. Figure 4-5 indicates that shorelines can be stable for a long time. It should be noted that the eroding, accreting, and stable beaches shown in Figures 4-3, 4-4, and 4-5
are on the same barrier island within a few miles of each other.
Net longshore transport rates along océan beaches range from near
zéro to 1 million cubic yards per year, but are typically 100,000 to
500,000 cubic yards per year. Such quantifies, if removed from a 10- to
20-mile stretch of beach year after year, would resuit in severe érosion
problems. The fact that many beaches hâve high rates of longshore transport without unusually severe érosion suggests that an equilibrium condi
tion exists on these beaches, in which the material eroded is balanced by
the material supplied; or in which seasonal reversais of littoral transport replace material previously removed.
4-2 LITTORAL MATERIALS
Littoral materials are the solid materials (mainly sedimentary)
the littoral zone on which the waves and currents act.
4«21 CLASSIFICATION
The characteristics of the littoral materials are a Pr^^sfifreto any Coastal engineering design. Médian grain size
Quently used design characteristic.
4,211 Size
Size Parameters. Littoral m^®rial'da^uid^lfse^eral
^ain size into clay, silt, sand, gravel, cob
Classification
size classifications exist, of which two, t e^^i^ie^^ Classification
( ased on the Casagrande Classification) an
Pipure 4-7.) The
are most commonly used in Coastal engineering.
4-H