GEODYNAMIC PHENOMENA OF THE POLISH COASTAL ZONE MAPPED AT THE SCALE 1:10 000
J. ZACHOWICZ1, R. DOBRACKI2, M.GRANICZNY3
1Polish Geological Institute, Branch of Marine Geology, 80-328 Gdańsk, st Kościerska. 5, Poland
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2Polish Geological Institute, Pomeranian Branch, 71-602 Szczecin, st Storrady 1, Poland
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3Polish Geological Institute, 00-975 Warszawa, st Rakowiecka 4, Poland
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The geodynamic map of the Polish coastal zone elaborated in the years 1995 – 97 covers about half of the Polish part of Baltic coastline. This map was developed at the Polish Geological Institute (Branches in Gdańsk and Szczecin) in the detailed scale 1:10 000. It presents the geological structure and the geodynamics of the coastal zone – land, backshore, beach and nearshore. On the background a wide spectrum of natural environment as well as utilisation and protection of its resources is presented, too.
Processes and phenomena, forming
the present shape of the coastline, are generated by many interrelated factors, such as: geologic structure, geomorphology, climatic phenomena, hydrologic and hydrodynamic conditions, biotic resources of the environment, type and way
of development and utilisation of the coastal zone. In the dynamic picture of the coastal zone, none
of these factors has an unequivocal and long lasting priority; also none of them can be viewed, analysed and interpreted without taking into account all other factors.
The Baltic coastal zone should be considered as a region of strong conflict between economical development (urbanisation, tourism, recreation, transport, industry) and the need to maintain
the natural landscape and the existing geo-ecosystems. Therefore, selection of a proper method of developing of the coastal zone resulting from its natural predisposition, is a basic task in
the process of economical utilisation of this zone.
Investigations carried out in the years 1995 – 97 enabled preparation of 32 map sheets. During this time content of Geodynamic Map, its utilisation and work plan for next map sheets preparation and digitalisation was discussed, too. Different field investigations and works were made for map preparation, among them: mapping, drilling (on land and sea), seismoacoustic, sonar and microseismic sounding. Laboratory asnalyses (grain size, petrography, heavy mineral composition and quantity, CaCO3 content), biostratigraphic analyses and expert opinions as well as 14C and TL age determination were performed, too. The map includes elements of geology, geodynamics, and evaluation of hydrogeological conditions, engineering geology and resource geology. Geological cross-sections are included at the each map sheet. Concept of the GIS date base structure was elaborated and two pilot sheets (Władysławowo and Rewal) have been made.
The MapInfo software was applied for its preparation.
The constantly occurring changes of the Polish coastline, progressing with different intensity, cause that this spatially and temporally diversified accretion – erosion system is becoming an extremely significant – if not the most important element for producing a basis for integrated and sustainable development of the Polish coastal zone. Coastal changes are typical example
of geoindicators. Shoreline position – coastal erosion, land use, sea levels, sediment transport and deposition etc. was selected as one of twenty-seven most important geoindicator.
Results obtained during the elaboration of the Map should be evaluated in two ranges. The basic range is the widening of information on
the geological structure of the coast and the correlation of the picture of geological structure
of the land and the sea bottom. Results of analyses and investigations unequivocally indicate that proper interpretation of the hydro- and geodynamic processes depends on accurate knowledge of the geological structure of the coastal zone.
The second range concerns the utilitarian results. Prediction indicates a continuing growth
of intensity of erosional processes. The strengthening of erosion results both from natural and anthropogenic causes. The hitherto stable, accumulative stretches of coast are gradually transforming into eroded coasts. Using various hydrotechnic structures counteracts this trend. However, this gives positive results in the short term only. In longer term, these structures disturb the litho- and morphodynamic balance and in effect intensify processes of coastal erosion.
At present, about 80% of the total length
of spit and alluvial coasts are eroded. These coasts can easily lose their role of barriers protecting
the land against inflows of seawater and against sea floods reaching far into the low-lying hinterland
of the coast.
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