Herrier J.-L., J. Mees, A. Salman, J. Seys, H. Van Nieuwenhuyse and I. Dobbelaere (Eds). 2005. p. 619-623
Proceedings ‘Dunes and Estuaries 2005’ – International Conference on Nature Restoration
Practices in European Coastal Habitats, Koksijde, Belgium, 19-23 September 2005
VLIZ Special Publication 19, xiv + 685 pp.
Morphodynamics of the central Swina Gate Barrier
foredunes (Polish coast) since 1995: a case study
Tomasz A. Łabuz
Institute of Marine Sciences, University of Szczecin,
Felczaka St. 3a, 71-412 Szczecin, Poland
E-mail: labuztom@univ.szczecin.pl
Abstract
The fieldwork was carried out on the Świna Gate Barrier shore (Polish Baltic coast). The
investigations were started after a strong storm surge, that washed out foredunes on the Polish
coast in November 1995. Since 1996, a new dune ridge has been observed to be expanding on the
still developing beach. Although affected by storm surges and wave action, the new ridge has been
persistent. The beach has becoming increasingly wider each year, more and more plants colonising
the new dune ridge.
Keywords: Foredune morphodynamics; Aeolian processes; Swina Gate Barrier (Poland).
Introduction
The foredune is the first dune ridge behind the beach zone where sand continues to
accumulate (e.g. Hesp, 1984; Carter et al., 1990). During 1-2 years, the ridge may
increase in height and grasses will stabilise it within the subsequent 5-8 years (Carter et
al., 1990). A developing coast and a progradating dune system of middle Świna Gate
Sandbar is a rarely encountered phenomenon on the Baltic coast. The multi-year
morphology changes on the investigated area show that particularly the middle part of
spit on Wolin has tendencies for rapid dune development.
Study area and methods
The study area is located on the islands of Wolin and Usedom on the Pomeranian Bay
coast (Fig. 1). In Poland, the spit extends for c. 16km from the morainic plateau at
Międzyzdroje (Wolin Island) to the state border in Świnoujście (Usedom Island). At
present, the entire barrier is covered by dune ridges formed during different
accumulation stages. The ridges differ in morphology, lithology, and trending to reveal
the consecutive phases of spit accretion and development. The youngest dunes, termed
the “white dunes”, have been forming since the 17th century. The study area is affected
primarily by westerly and southerly (S, SW, W) winds (as recorded over 1961-1995 in
the town of Świnoujście), while the north-easterly winds are the heaviest. Prolonged
wind action enhances material transport from beaches located west and east of the area
- 619 -
T.A. Łabuz
to its central part. The upper beach is built up mostly by medium and fine sand (35 and
60%, respectively). The material building the foredune ridge contains up to 85% of fine
and very find sand and not more than 15% of medium sand. In winter, the importance of
medium sand in the foredune increases (to 30- 40%) in winter. Plant species typical sand
accumulation on young dunes or dune fields include the psammophilous Ammophila
arenaria, Calammophila baltica and Elymus arenarius and the halophilous Honckenya
peploides. Other plants are characteristic of older fixed dunes.
A
D
The study involved measuring B
(i) dune relief changes, (ii)
Po mera nia n
vegetation dynamics, (iii) A
B
POLAND
hl
Bay
be
human or animal influences,
ck
Transect 420.6km
(iv) storm surges impact, and
oje
zd r
(v)
wind
impact.
The
Study area
dz y
Św
Mię
ino
ujś
measurements were taken
cie
C
WOLIN
several times during the year,
ISLAND
a
l
particularly – and whenever U S E D O M
u
ns
ni
Św
e
P
ISLAND
ina
possible – after every major
r
tó
zy
Wicko Lake
Pr
manifestation
of
factors
White dunes
412 Kilometres of
Polish coas
impacting the dunes. Relief
Transverse
Main roads
dunes
State border
changes were measured with
Yellow dunes
Moraines
Brown dunes
geodesic devices from fixed
plots (5x5m) along transects
Fig. 1. Location of the Swina Gate Barrier (B) on the Southern
Baltic (A); study area (C); wind rose (D).
(1km apart, in various areas).
Other measurements provided
comprehensive information on the dynamics of the entire environment, e.g.: sand grain
size, wind fields, vegetation dynamics or storm surges. The study is a part of the author’s
project focusing on the entire belt coastal dunes in Poland called ANDDY
(Anthropogenic-Natural Dunes Dynamics; web pages: bramaswiny.szc.pl and
polishdunes.szc.pl). The aim of the paper is to describe the development of the central
part of the Świna Gate Barrier (Polish coastline kilometre 420-421; Fig. 1).
N
Świnoujście
(1961-1995)
NW
SWEDEN
NE
BALTIC SEA
Rugen
SW
SE
Pomeranian
Bay
GE
RM
A
NY
S
428
Gulf of
Gdańsk
Szczecin
412
Human
impact
427
426
RUSSIA
Gdańsk
O
de
r
Human
impact
E
Vi
stu
la
00
W
LITHUANIA
Bornholm
15
425
424
Human
impact 413
Human
impact
415
414
416
423
422
421 420
419
418
417
Foredune morphodynamics
In 1995, the upper beach of the area between 420-421km, up to 30m from the foredune,
featured numerous small, 0.1 to 0.5m high, aeolian forms and was vegetated by pioneer
plants. Hillocks on the beach were separated from each other by deflation depressions,
the blow-outs, with organic material accumulated on their bottoms. The mean width of
the beach was about 60-90m. The seaward slope of the foredune, i.e. the dune ridge
closest to the beach and not yet stabilised, was abraded. The foredune measured up to
4m in height. In late autumn 1995, a very strong storm (surging to 1.5m above ASL)
destroyed the beach’s dense hillocks and plant habitats. It also cut the foredune off
and/or washed it away in many places. In late spring 1996, however, the upper beach
was again covered by numerous small aeolian forms. Locally, the foredune still showed
an abraded seaward slope, but storm gaps were in many places filled up by the
accumulated sand. Rather low (up to 0.2m) sandy “tongues” were seen on the foredune
top. As of 1997, the hillocks were growing in size (Fig. 2). In some places they
- 620 -
Morphodynamics of the central Swina Gate Barrier foredunes (Polish coast)
connected with the foredune slope and looked like long, grass-fixed tongues running
across the ridge and the water line. The increasingly denser grasses entrapped
progressively higher amounts of sand. The highest hillocks and grasses posed major
obstacles to the aeolian transport. Consequently, sand accumulation on the foredune was
clearly diminishing, whereby the ridge was slowly becoming stabilised (by other plants).
As a result of aeolian accumulation, the abraded seaward slope of the dune became
initially transformed into a gently-shaped form. Between the ridge and a new one that
was growing a deflation depression – a blow-out – appeared. Between 1998 and 2000,
the narrow depressions between the hillocks were filled up by the sand. The embryo
dunes became linked into a single dune ridge, parallel to the old one. The landward slope
of that ridge was steep, the seaward one being flat. The new foredune did not have any
straight ridge. It was a single ridge consisting of joined-together tops of the embryo
dunes. Ridges of the embryo dunes run transverse to the new foredune ridge. The ridge
described reached up to 2m. In front of it accumulation process and plant succession
started again. In autumn and winter 2001, a few heavy storms (water level to 1.5m above
ASL) damaged the dunes, with several storm gaps appearing in the foredune ridge of the
studied area. The gaps, wider than 20m, allowed sea water incursions to the low-lying
ground behind the foredune. No storms affected the area in winter 2002. It was only the
ice cover of the beach that stopped sand transport from the lower beach in the direction
of the foredune direction. In spring 2002, the sand accumulation process started filling
all the gaps and gates in the foredune. The next cold season proceeded without storms;
the accumulation was very small (0.1-0.2m), even on fixed dunes. In spring 2003, the
foredune was up to 3m high. The low-lying part behind it became stabilised. During the
growing season, a slow colonisation by mosses and lichens was observed. The sand was
transported only through the storm gates where an active surface was visible. In autumn
2003, the foredune ridge was damaged by a single storm surge (with water reaching
1.5m above the ASL) and the entire upper beach was levelled off. The dune hillocks (up
to 0.6m high) were cut off and the deflation depressions were filled with sand; the beach,
however, was still c 70-90m wide. The heavy wind during the storm in question
produced aeolian accumulation on the surfaces behind the foredune, fixed previously by
mosses. In early spring, the sand, blown over the foredune from places that had not been
ice-covered, accumulated on it, producing an 0.4m thick layer; the sand accumulated
also in the previously stabilised depression between the first two dunes. In spring, the
foredune was 4m (ASL) high and completely covered by grasses. Until summer 2004,
the upper beach was covered by numerous hillocks 0.3-0.7m high. They were covered by
grasses growing at a density comparable to that observed in 1997.
Conclusions
The foredune in the central part of the barrier is not sufficiently stabilised by grasses and
wide enough to withstand heavy storms. The foredune has been rising for the last 9
years. The former foredune had emerged in the area between 1986 and 1995; its
formation took 9 years as well. Last autumn (2004), the foredune began to be colonised
by plants that, as opposed to those that had been establishing themselves before, were
not tolerant of sand fill-up.
- 621 -
T.A. Łabuz
R o ad s, fo otp a ths
1986
N
A
Beach
B
B
Sea
7m
6
5
4
3
2
1986
Forest road
A
Forest road
BEACH
Footpath
Forest road
B
Transect 420.6km /azimuth N
Profile from map of
Polish coast. Plant
ranges from air photos.
[m]
6
1986
4
2
0
40
0
A new foredune emerged
during 11 years. A strong
storm surge in Nov. ‘95
washed away dunes in
many places
120
80
(No data) A
1995 - no transect
data
[m]
6
1997.07
4
2
0
40
0
120
80
A
D
E
A new foredune was built.
Plant succession partly
fixed old foredune.
C
6
2001.04
4
2
420.6 km /N
40
0
160 [m]
6
2002.05
4
2
420.6 km /N
0
0
40
120
80
B
C
E
160 [m]
A
[m]
6
2003.07
4
2
0
0
40
120
80
D
160 [m]
A
B
C
E
[m]
6
2004.03
4
2
0
0
40
160 [m]
120
80
No data in winter
D
Still accumulation on
foredune ridge and on
upper beach.
Very dense plants
species are covering
whole beach
(rapid succession).
A
B
C
E
[m]
D
Strong storm did not
break dune ridge in
middle part of barrier.
Plants will again stop
sand during groving
season.
120
80
D
Rebuild foredune. Fixed
surface in lower part
between ridges.
Succession on beach
& embryo dunes growth.
160 [m]
B
[m]
0
Foredune cut off after
several storms (winter
2001/02).
Plants begin again to
trap sand on beach.
160 [m]
B
D C
E
E
B
C
A
[m]
2004.09
6
4
2
0
0
40
120
80
D
E
C
160 [m]
B A
Psamophilous grasses A - halophytes
B - psammophilous grasses, Elymo-Ammophiletum habitats
C - other psammophytes, Helichryso-Jasionetum habitats
Willow shrubs
D - trees, Empetro-Nigri Pinetum habitats
Pine trees
E - Mosses & lichens
Fig. 2. Foredune morphodynamics with habitat changes in the central part of the
Swina Gate Barrier: an example transect at km 420.6 off the Polish coast.
- 622 -
Morphodynamics of the central Swina Gate Barrier foredunes (Polish coast)
The new initial field of the foredune (third since 1986) was 30-40m wide, consisting of
dune hillocks (shadow and embryo dunes) up to 1m high, densely vegetated by grasses.
New dunes in the area do not develop at an identical rate; instead, the rate varies due to
the wind and storm events. The winter season in the area may feature numerous storms
one year (as in winters of 1995/6, 2001/2 or 2003/4) to be devoid of them next year. The
same is true with respect to the wind regime. As a result of all the factors, new dunes
emerge and will probably do so in the future. Storm surges are causing abrasion of the
dunes but supply the beach with material. Low thickness of sand helps in aeolian
transportation along barrier beaches. Absence of mass tourism leads to natural dune
development in the middle part of the investigated barrier.
References
Carter R.W.G. and P. Wilson. 1990. The geomorphological, ecological and pedological
development of coastal foredunes at Magilligan Point. p.129-157. In: Nordstrom
K.F., N.P. Psuty and B. Carter. (Eds). Coastal dunes. Wiley & Sons, Chichester.
Hesp P.A. 1984. Foredune formation of southeast Australia. P.69-97. In: Coastal
Geomorphology in Australia. Academic Press, Sydney. Thom B.G. (Ed).
- 623 -