3. Sédiment Transport
65
inter-linked segments of the original Coastal line and the assumption is that
the sédiment transport within each segment/unit is mostly self-contained
with minimum influence on the adjacent/neighbouring cells. However each
cell can hâve its own sources (inputs) and sinks (outputs). The division of
the coast into manageable segments has to be done carefully considering
the spatial and temporal variations in the Coastal geomorphology as well
as the associated nearshore sédiment transport processes. This approach is
known as the sédiment cell concept. The sédiment cell concept proposed
by Van Rijn [1997, 2011] has been widely adopted for Coastal engineering
applications. Adopting this method the Coastal stretch can be conveniently
subdivided into smaller self-contained cells or compartments without losing/ sacrificing its integrity. It has been well established that the nearshore
sédiment movements occur in discrète areas of cells called sédiment cells,
within which inputs and outputs are balanced.
A sédiment cell is defined as a stretch of coastline and its nearshore area
within which the movement of coarse sédiments is largely self-contained. In
other words, these are distinct areas of coastline (including the offshore
part) separated from the adjoining Coastal stretches by well-defined boundaries, such as natural headlands, artificial structures projecting into the
sea, natural inlets etc. The general assumption is that the movement of
sédiments within a cell will not hâve any major effect on the adjacent cells.
Even though theoretically, sédiment cells are considered as closed Systems
without any loss or gain, in reality, there is a possibility that some of the fine
sédiments may move around headlands or obstructions and eventually enter
into the neighbouring cells. Hence, wherever there is a significant change
in the Coastal processes within a sédiment cell, sub-cells within the major
cells can be considered and further division of sub-cells also can be carried
ont if required at meso- and micro-level for a detailed investigation. This
type of sub-cell level studies becomes necessary, when, the Coastal processes
differ significantly at certain locations within a cell. The cell and sub-cell
boundaries are usually defined at locations, where, there is a discontinuity
in the transport rate or change of direction (probably could be due to the
presence of headlands, spits, river mouths etc.). These boundaries need not
be always of natural origin. Hard structures like jetties, breakwaters, long
groins etc. which are normally shore connected can be considered as artificial boundaries for defining a sédiment cell especially when the structures
are long enough to extend beyond the surf zone.
The concept of Sédiment Cell is explained taking the Kérala coast
located along the SW coast of India as an example. Adopting the sédiment
65
inter-linked segments of the original Coastal line and the assumption is that
the sédiment transport within each segment/unit is mostly self-contained
with minimum influence on the adjacent/neighbouring cells. However each
cell can hâve its own sources (inputs) and sinks (outputs). The division of
the coast into manageable segments has to be done carefully considering
the spatial and temporal variations in the Coastal geomorphology as well
as the associated nearshore sédiment transport processes. This approach is
known as the sédiment cell concept. The sédiment cell concept proposed
by Van Rijn [1997, 2011] has been widely adopted for Coastal engineering
applications. Adopting this method the Coastal stretch can be conveniently
subdivided into smaller self-contained cells or compartments without losing/ sacrificing its integrity. It has been well established that the nearshore
sédiment movements occur in discrète areas of cells called sédiment cells,
within which inputs and outputs are balanced.
A sédiment cell is defined as a stretch of coastline and its nearshore area
within which the movement of coarse sédiments is largely self-contained. In
other words, these are distinct areas of coastline (including the offshore
part) separated from the adjoining Coastal stretches by well-defined boundaries, such as natural headlands, artificial structures projecting into the
sea, natural inlets etc. The general assumption is that the movement of
sédiments within a cell will not hâve any major effect on the adjacent cells.
Even though theoretically, sédiment cells are considered as closed Systems
without any loss or gain, in reality, there is a possibility that some of the fine
sédiments may move around headlands or obstructions and eventually enter
into the neighbouring cells. Hence, wherever there is a significant change
in the Coastal processes within a sédiment cell, sub-cells within the major
cells can be considered and further division of sub-cells also can be carried
ont if required at meso- and micro-level for a detailed investigation. This
type of sub-cell level studies becomes necessary, when, the Coastal processes
differ significantly at certain locations within a cell. The cell and sub-cell
boundaries are usually defined at locations, where, there is a discontinuity
in the transport rate or change of direction (probably could be due to the
presence of headlands, spits, river mouths etc.). These boundaries need not
be always of natural origin. Hard structures like jetties, breakwaters, long
groins etc. which are normally shore connected can be considered as artificial boundaries for defining a sédiment cell especially when the structures
are long enough to extend beyond the surf zone.
The concept of Sédiment Cell is explained taking the Kérala coast
located along the SW coast of India as an example. Adopting the sédiment