CHANGES OF THE COAST OF LAKE PEIPSI DURING THE LAST DECADES
E. TAVAST
Institute of Geology at Tallinn Technical University, 10143 Tallinn, 7 Estonia Ave, Estonia
e-mail: Tavast@gi.ee
Peipsi is one of the largest lakes in Europe
(3555 km2). Water level fluctuations in the lake are
considerable. During the last 90 years an amplitude
of 3.04 m has been registered. The lowest water
level in the last century was registered on
November 7, 1964 (28.72 m a.s.l.) and the highest
on May 12, 1924 (31.76 m a.s.l.). There are about
11 year periods of high and low water level stands
(Jaani,1973). After the great flood of 1924, the first
serious steps were taken to lower the water level of
the lake through improving the outflow conditions
at the head of the Narva River. The river channel
was dredged at a length of 10 km. The limestone
and boulders, removed from the river channel, were
used for defending constructions.
Very deep and short waves are characteristic of
L. Peipsi. During high water level their effect on
the coast and buildings is considerable. The profile
of equilibrium is formed at the coast by usual
winds. When the speed of wind is 10-15 m/s the
scarps up to 50-60 cm in height, festons and small
beach ridges are formed on the beach. During the
next storm these will be smashed and the new
balance profile comes into being. Considerable
changes take place when the speed of wind reaches
above 20 m/s.
Lake Peipsi has a more open eastern and
northern and more swampy and overgrown western
bank. Due to the prevailing south-westerly and
westerly winds active erosion-accumulative or
erosional shores are spread in the northern and
eastern parts of the lake. Swampy shores overgrown
with bushes, bulrush and reed are characteristic of
the western and southern parts. The intensity of
erosion and accumulation processes of beaches are
cyclically changing. During 1987-1993, erosion
became more intensive, even at some sites at the
western coast. The coast in the northern part of the
lake retreated several metres during those years
(Tavast, Raukas, 1996). At the end of November
1987, strong wind blew from the south and southwest and on the northern coast the water rose more
than 0.5 m above its usual level. The beach suffered
remarkable damage. In some places the shore
retreated 4-5 m (Fig. 1). Over the course of the last
six years (1995-2000), the erosion processes have
diminished. The accumulation processes prevail at
those sites where some years ago erosion was
remarkable.
We have investigated the dynamics of the lake
shore since 1981 and collected a lot of factual data
to predict possible changes in the coming future.
Fig. 1. Changes of the northern coast of the L. Peipsi since 1982 at different water level near the Kuru Village.
REFERENCES
Jaani, A. 1973. Cyclic changes in the abundance of
water (in Estonian). – Eesti Loodus, 12, 758–
764.
Tavast, E., Raukas, A. 1996. Geological
development of the Northern Coast of Lake
Peipsi. – Journal of Coastal Research, 12, 4,
1024–1033.
33