Sédiment budget studies hâve been presented by Johnson (1959), Bowen
and Inman (1966), Vallianos (1970), Pierce (1969), and Caldwell (1966).
4.712 Eléments of Sédiment Budget. Any process that increases the
quantity of sand in a defined control volume is called a source. Any
process that decreases the quantity of sand in the control volume is
called a sink. Usually, sources are identified as positive and sinks
as négative. Some processes (longshore transport is the most important)
function both as source and sink for the control volume, and these are
called convecting processes.
Point sources or point sinks are sources or sinks that add or subtract sand across a limited part of a control volume boundary. A tidal
inlet often functions as a point sink. Point sources or sinks are generally measured in units of volume per year.
Line sources or line sinks are sources or sinks that add or subtract
sand across an extended segment of a control volume boundary. Wind transport landward from the beaches of a low barrier island is a line sink for
the océan beach. Line sources or sinks are generally measured in units of
volume per year per unit length of shoreline. To compute the total effect
of a line source or sink, it is necessary to multiply this quantity by the
total length of shoreline over which the line source or sink opérâtes.
The following conventions are used for éléments of the sédiment
budget :
Q* is a point source
Q-f is a point sink
q£ is a line source
q^ is a line sink
These subscripted éléments
in Table 4-13 according to
of the sédiment budget are identified by name
_
whether the element makes a point or line conution to the littoral zone, and according to the boundary across which
e contribution enters or leaves. Each of the éléments is discussed in
following sections.
The length of shoreline over which a line source is active is in
dicated by b{ and the total contribution of the line source or line
Slnk by Q^+ or qJ“, so that in general
Q* =
•
(4-46)
4-117
and Inman (1966), Vallianos (1970), Pierce (1969), and Caldwell (1966).
4.712 Eléments of Sédiment Budget. Any process that increases the
quantity of sand in a defined control volume is called a source. Any
process that decreases the quantity of sand in the control volume is
called a sink. Usually, sources are identified as positive and sinks
as négative. Some processes (longshore transport is the most important)
function both as source and sink for the control volume, and these are
called convecting processes.
Point sources or point sinks are sources or sinks that add or subtract sand across a limited part of a control volume boundary. A tidal
inlet often functions as a point sink. Point sources or sinks are generally measured in units of volume per year.
Line sources or line sinks are sources or sinks that add or subtract
sand across an extended segment of a control volume boundary. Wind transport landward from the beaches of a low barrier island is a line sink for
the océan beach. Line sources or sinks are generally measured in units of
volume per year per unit length of shoreline. To compute the total effect
of a line source or sink, it is necessary to multiply this quantity by the
total length of shoreline over which the line source or sink opérâtes.
The following conventions are used for éléments of the sédiment
budget :
Q* is a point source
Q-f is a point sink
q£ is a line source
q^ is a line sink
These subscripted éléments
in Table 4-13 according to
of the sédiment budget are identified by name
_
whether the element makes a point or line conution to the littoral zone, and according to the boundary across which
e contribution enters or leaves. Each of the éléments is discussed in
following sections.
The length of shoreline over which a line source is active is in
dicated by b{ and the total contribution of the line source or line
Slnk by Q^+ or qJ“, so that in general
Q* =
•
(4-46)
4-117