érosion accoœpanied by longshore transport which has carried sand along
the coast to supply the barriers and spits extending across the bays.
The primary agent producing this érosion and transport is the action of
waves impinging on the shore.
Littoral transport is the movement of sedimentary material in the
littoral zone by waves and currents. The littoral zone extends from the
shoreline to just beyond the most seaward breakers.
Littoral transport is classified as onshore-offshore transport or as
longshore transport. Onshore-offshore transport has an average net direc
tion perpendicular to the shoreline; longshore transport has an average
net direction parallel to the shoreline. The instantaneous motion of
sedimentary particles has both an onshore-offshore and a longshore component. Onshore-offshore transport is usually the most significant type
of transport in the offshore zone, except in régions of strong tidal
currents. Both longshore and onshore-offshore transport are significant
in the surf zone.
Engineering problems involving littoral transport generally require
answers to one or more of the following questions:
(a) What are the longshore transport conditions at the site?
(Needed for the design of groins, jetties, navigation channels, and
inlets.)
(b) What is the trend of shoreline migration over short and long
time intervals? (Needed for design of Coastal structures, including
navigation channels.)
(c) How far seaward is sand actively moving? (Needed in the design
of sewage outfalls and water intakes.)
(d) What is the direction and rate of onshore-offshore sédiment
motion? (Needed for sédiment budget studies and beach fill design.)
(e) What is the average shape, and the expected range of shapes,
for a given beach profile? (Needed for design of groins, beach fills,
navigation structures and flood protection.)
(f) What effect will a postulated structure or project hâve on
adjacent beaches and on littoral transport? (Needed for design of ail
Coastal works.)
This section présents recommended methods for answering these and
related questions. The section indicates accepted practice based on
leld observations and research results. Section 4.52 deals with onshore
n/\?re \ransp°rt, presenting material pertinent to answering questions
roug ( ). Section 4.53 deals with longshore transport, presenting
material pertinent to questions (a), (b), and (f) .
4-52
the coast to supply the barriers and spits extending across the bays.
The primary agent producing this érosion and transport is the action of
waves impinging on the shore.
Littoral transport is the movement of sedimentary material in the
littoral zone by waves and currents. The littoral zone extends from the
shoreline to just beyond the most seaward breakers.
Littoral transport is classified as onshore-offshore transport or as
longshore transport. Onshore-offshore transport has an average net direc
tion perpendicular to the shoreline; longshore transport has an average
net direction parallel to the shoreline. The instantaneous motion of
sedimentary particles has both an onshore-offshore and a longshore component. Onshore-offshore transport is usually the most significant type
of transport in the offshore zone, except in régions of strong tidal
currents. Both longshore and onshore-offshore transport are significant
in the surf zone.
Engineering problems involving littoral transport generally require
answers to one or more of the following questions:
(a) What are the longshore transport conditions at the site?
(Needed for the design of groins, jetties, navigation channels, and
inlets.)
(b) What is the trend of shoreline migration over short and long
time intervals? (Needed for design of Coastal structures, including
navigation channels.)
(c) How far seaward is sand actively moving? (Needed in the design
of sewage outfalls and water intakes.)
(d) What is the direction and rate of onshore-offshore sédiment
motion? (Needed for sédiment budget studies and beach fill design.)
(e) What is the average shape, and the expected range of shapes,
for a given beach profile? (Needed for design of groins, beach fills,
navigation structures and flood protection.)
(f) What effect will a postulated structure or project hâve on
adjacent beaches and on littoral transport? (Needed for design of ail
Coastal works.)
This section présents recommended methods for answering these and
related questions. The section indicates accepted practice based on
leld observations and research results. Section 4.52 deals with onshore
n/\?re \ransp°rt, presenting material pertinent to answering questions
roug ( ). Section 4.53 deals with longshore transport, presenting
material pertinent to questions (a), (b), and (f) .
4-52