520
J. Ojeda Zújar et al.
i) during the first period (1979-89) all change was by marine erosion of
the foredune’s seaward side, as the foredune, and especially its landward
side, was well controlled by vegetation. Anthropic pressure was very low
in this period and concentrated in the built-up areas of La Antilla and
Isla Cristina
ii) in the second period (1989-94), foredune retreat rate actually doubles
but is spatially concentrated in the western sector. Yet, because of the
higher incidence of tourist pressure and the opening of the first camping
sites, the vegetation is beginning to be destroyed by overdune paths and
landward dune migration begins although it is as yet only 1/6 of the
seaward face's retreat rate
iii) during the third period (1994-94), rates of retreat on the seaward side
are up to 6 times those of the first period, even though in this case the
spread of marine erosion is more homogenous. Moreover, the rates of
foredune landward migration continue at similar rates despite having a
reduced width of dune to draw on for material
In summary the three phase evolution of coastal erosion in this zone is:
1979-89; a well developed foredune, with two ridges, and fixed by vegetation becomes
a seaward eroded foredune with a landward slope still controlled by vegetation. This
evolution is explained by sediment deficit caused by the combined impact of jetties and
dam-regulated river discharges. Anthropic pressure is scant.
1989-94; expansion of built-up areas and the development of camp sites intensifies
anthropic pressure, especially cross-dune paths to the beach. The sedimentary deficit
continues to increase. At the same time the dunes are weakened by vegetation loss and
lowered by deflation which together produce landward-moving blow-outs.
1994-96; sediment deficit continues to increase for the same reasons as before and
anthropic pressure is yet stronger, because of more camp sites and increased occasional
visits. Blow-outs increase and the heavy storms in the winter of 1995 meant that in
some places the foredune disappeared leaving many of the pines to die subsequently
from the combined effects of the wind, sand, and salt spray.
Foredune Volume Calculation and Sediment Budget
The possibility of obtaining altimetric data from whichever of the sources used has
made it possible to characterize these changes in even greater detail. The first stage
was to establish how much sediment the foredune had lost or gained, which required
the construction of DTMs from the available data. Here we present just the DTMs for
1989 and 1994 (Fig. 6). For these two reference dates the measurements come from the
J. Ojeda Zújar et al.
i) during the first period (1979-89) all change was by marine erosion of
the foredune’s seaward side, as the foredune, and especially its landward
side, was well controlled by vegetation. Anthropic pressure was very low
in this period and concentrated in the built-up areas of La Antilla and
Isla Cristina
ii) in the second period (1989-94), foredune retreat rate actually doubles
but is spatially concentrated in the western sector. Yet, because of the
higher incidence of tourist pressure and the opening of the first camping
sites, the vegetation is beginning to be destroyed by overdune paths and
landward dune migration begins although it is as yet only 1/6 of the
seaward face's retreat rate
iii) during the third period (1994-94), rates of retreat on the seaward side
are up to 6 times those of the first period, even though in this case the
spread of marine erosion is more homogenous. Moreover, the rates of
foredune landward migration continue at similar rates despite having a
reduced width of dune to draw on for material
In summary the three phase evolution of coastal erosion in this zone is:
1979-89; a well developed foredune, with two ridges, and fixed by vegetation becomes
a seaward eroded foredune with a landward slope still controlled by vegetation. This
evolution is explained by sediment deficit caused by the combined impact of jetties and
dam-regulated river discharges. Anthropic pressure is scant.
1989-94; expansion of built-up areas and the development of camp sites intensifies
anthropic pressure, especially cross-dune paths to the beach. The sedimentary deficit
continues to increase. At the same time the dunes are weakened by vegetation loss and
lowered by deflation which together produce landward-moving blow-outs.
1994-96; sediment deficit continues to increase for the same reasons as before and
anthropic pressure is yet stronger, because of more camp sites and increased occasional
visits. Blow-outs increase and the heavy storms in the winter of 1995 meant that in
some places the foredune disappeared leaving many of the pines to die subsequently
from the combined effects of the wind, sand, and salt spray.
Foredune Volume Calculation and Sediment Budget
The possibility of obtaining altimetric data from whichever of the sources used has
made it possible to characterize these changes in even greater detail. The first stage
was to establish how much sediment the foredune had lost or gained, which required
the construction of DTMs from the available data. Here we present just the DTMs for
1989 and 1994 (Fig. 6). For these two reference dates the measurements come from the