345 
.s were made 
Here vegetation starts when there is some stabilisation in the sand transport. 
performed 
. These field 
The area below the high tension pylon shows an example of such a "flying" start 
(compare figure 48 from ZONNEVELD 1959(60) extreme left). The rest of that 
3S of photo- 
figure shows a more general building up of sediments. From other permanent 
irror- 
sample areas we know places where the youngest stages have not changed very 
plectus 
much in vegetation or elevation in more than 15 years. 
dinaoea 3 
tifolia s 
egetation 
lotographed 
d described 
However, in the area under discussion we see a dynamic change. Directly after 
the sandbar was more or less stabilized (around 1945) several Soirpus species 
arrived (Soirpus maritimus 3 Soirpus triqueter 3 Soirpus laoustris glauous). 
The first pylon photo (1950) shows an open pioneer vegetation with rounded 
stands of Soirpus marztimus as a clear dominant, and with some smaller 
submerged 
patches of Soirpus triqueter 3 Soirpus laoustris glauous (tabernaemontani). 
Also found were one example of Butomus umbellatus and one of Typha angusti- 
ice in order 
folia. The altitude of the top of the accretion was about 80 cm. below mean 
high water, which is near the limit between the so called high and low backswamp, 
and increasing 
s visual 
i. e. high and low levee (cf ZONNEVELD 1959(60) legend vegetation map). These 
species combinations show that the whole area belongs to the Soirpetum trique- 
tri et maritimi but that already the first "germs" were available for the 
the various 
Soirpeto phragmitetum-Sagittaria variant (a vegetation usually dominated by 
aracterized 
Soirpus laoustris and even (on the highest point) for the typical variant (a 
riefly 
g. 132). 
ed until 
community with usually Typha species and or Phragmites as dominant). During 
the following years we see first a strong increment of Soirpus maritimus and a 
decrease of Soirpus triqueter and Soirpus laoustrus glauous tabernamontani . 
anthropogenic 
Phalaris arundinaoea appears on the scene around 1953. This means that the 
Soirpetum triquetri et maritimi typioum shifts over to the Soirpetum tri- 
nde of about 
quetri et maritimi phalaridetosum. An interesting feature from the geomorpho- 
when the 
logical point of view follows from the comparison of the photographs from 1950, 
.dating a 
1951, and 1952. In 1950 the accretion is almost level, gradually falling to the 
large tidal gullies at both sides. In 1951 "suddenly" a great number of small 
of the 
gullies originate. Two of these appear to have developed already in 1952 into 
was closed 
clear meandering gullies which extend to the centre of the accretion, the others 
remain smaller and disappear after 1953. The explanation is that prior to 1950, 
! for this area 
the vegetation is very sparse. Tidal waters have almost no hinderance and flow 
to an amplitude 
quickly on and off the accretion. In 1951, however, the vegetation is already 
s. 
rather dense and it is able to hold back the water a little, so that during the 
3 distinguished. 
a speed too 
ebb-tide there is a small period of a "steady" stream just sufficient to induce 
gully formation. In 1952 the vegetation is already dense, and mud accumulation