122
R.H. Chaxlier and Chr. P. De Meyer
Chapter V : Coastal Morphology
1
Introduction
In coastal areas morphological evolutions are usually reflected in changes in the
shoreline position, and these changes are often decisive in taking measures
against coastal erosion or not. Morphological developments can be divided into
short-term and long-term evolutions. A clear distinction between these two types
of evolution as far as time scale is concerned cannot be made. However, in the
light of beach erosion and possible protection measures one should usually think
in terms of periods of decades in the case of long-term evolution. The time scale
of short-term evolution may be quite variable. Sometimes the morphological
changes during a single storm may be significant, but also yearly variations in the
wave climate may cause developments which can be denoted as short-term
phenomena.
In decision making whether to take beach protection measures, the long-term
developments are of particular importance. Yet, this decision may be actuated by
short-term developments, e.g., a single storm may cause a temporary but
unacceptable retreat of the coastline or erosion of the dunes, so that beach
protection measures are urgently required.
The cross-shore transport, and thus the variation in the coastal profile, is mainly
responsible for the short-term fluctuations in the coastline, while the long-term
evolution of the coastline is mainly governed by the gradients in the longshore
transport. Therefore attention will first be paid to the development of coastal
profiles. Subsequently the long-term morphological evolutions will be treated,
and the available mathematical models for computing such morphological
evolutions subsequently briefly described.
2
Coastal Profiles
Tile form of the coastal profile and their form the variations are mainly governed
by the cross-shore transports. These transports and the resulting coastal profile,
are closely related to wave motion, and because of the variability of the wave
conditions in nature, the form of the coastal profile is also quite variable. This
variability is most pronounced in the nearshore zone where the cross-shore
transports are largest.
R.H. Chaxlier and Chr. P. De Meyer
Chapter V : Coastal Morphology
1
Introduction
In coastal areas morphological evolutions are usually reflected in changes in the
shoreline position, and these changes are often decisive in taking measures
against coastal erosion or not. Morphological developments can be divided into
short-term and long-term evolutions. A clear distinction between these two types
of evolution as far as time scale is concerned cannot be made. However, in the
light of beach erosion and possible protection measures one should usually think
in terms of periods of decades in the case of long-term evolution. The time scale
of short-term evolution may be quite variable. Sometimes the morphological
changes during a single storm may be significant, but also yearly variations in the
wave climate may cause developments which can be denoted as short-term
phenomena.
In decision making whether to take beach protection measures, the long-term
developments are of particular importance. Yet, this decision may be actuated by
short-term developments, e.g., a single storm may cause a temporary but
unacceptable retreat of the coastline or erosion of the dunes, so that beach
protection measures are urgently required.
The cross-shore transport, and thus the variation in the coastal profile, is mainly
responsible for the short-term fluctuations in the coastline, while the long-term
evolution of the coastline is mainly governed by the gradients in the longshore
transport. Therefore attention will first be paid to the development of coastal
profiles. Subsequently the long-term morphological evolutions will be treated,
and the available mathematical models for computing such morphological
evolutions subsequently briefly described.
2
Coastal Profiles
Tile form of the coastal profile and their form the variations are mainly governed
by the cross-shore transports. These transports and the resulting coastal profile,
are closely related to wave motion, and because of the variability of the wave
conditions in nature, the form of the coastal profile is also quite variable. This
variability is most pronounced in the nearshore zone where the cross-shore
transports are largest.