Geological Hazard Potential at the Baltic Sea and Its Coastal Zone: Examples from the Eastern Gulf of Finland and the Kaliningrad Area - The Baltic Sea Basin - page 355

destabilizes the system. Nowadays, there is a dynamic correlation between coastal
erosion and the state of the submarine terrace, i.e., the more the terrace erosion
the greater the on-land problems. The situation becomes even more problematic
because of the ineffective old system of coastal protection measures (Fig. 16.7 ) and
the intense and unsustainable development of recreation infrastructure.
16.5.2.3 Ice Impact
In the eastern Gulf of Finland, ice impact is the second important factor of coastal
erosion. These processes are most dangerous during winter floods when 1-m-thick
ice layers can damage shallow water areas of the gulf bottom upon the depth of
30-50 cm and remove frozen blocks of sediments and even big boulders along
the beach face. Ice damages trees and coastal buildings as well as coast protection
structures.
16.5.2.4 Slope Slides
Landslides in the eastern Gulf of Finland are observed locally along some parts of
the coast between the capes Flotsky and Peschany and in the vicinity of the town of
Lebyazhye (Krasnaya Gorka fortress, southern coastal zone) where the coastal cliffs
reach 25-30 m height.
The geological structure of the upper sediment layers plays an important role
in the landslide processes. In the southern coastal zone, clays of Kotlin horizon of
Vendian are overlapped by 5-m-thick Quaternary deposits. The intense wetting of
Vendian clays and the occurrence of microfractures (especially within tectonic faults
zones) lead to a decrease of property strength and can cause landslides (Auslender
et al. 2002 ) .
16.5.2.5 Sea Bottom Sediment Pollution
The problem of bottom sediment pollution was not the focus of our studies.
Although it cannot be classified as a geological hazard itself, the risk assessments
should keep this problem in mind for any hydroengineering activities, i.e., dredg-
ing, dumping, and pipeline construction. Within the Russian sector of the Baltic Sea,
the most polluted areas are the lagoons adjacent to the big cities of St. Petersburg
and Kaliningrad - the Neva Bay and the Vistula Lagoon (Spiridonov et al. 2004 ,
Emelyanov et al. 1998 ) . Mud of depositional basins can form a huge sink for spe-
cial chemical substances. In the eastern Gulf of Finland, an extended and prolonged
seafloor anoxia within local coastal depositional basins could therefore enhance
the environmental problems by releasing metals and nutrients from the seafloor
sediments (Kotilainen et al. 2007 ) . The possible consequence of these pollution
processes is discussed in Chapter 17 .