Permafrost

42
Dynamics of the Baydaratskaya Bay Coasts (Kara Sea) in the Area of
the Gas Pipeline Underwater Crossing Design
N.G. Belova, S.A. Ogorodov, A.M. Kamalov, A.I. Noskov
(Russia, Faculty of Geography, Lomonosov Moscow State University,E-mail: nataliya-belova@yandex.ru)
Abstract: Coastal zone of the sea is an area of interaction between lithosphere, hydrosphere
and atmosphere and an extraordinary high dynamic activity. Morpholithodynamic conditions in
the coastal zone are one of the factors to select the site of pipelines crossing from the offshore
slope to the land and a value of pipeline deepening.
More than a half of the Baydaratskaya Bay of Kara Sea coastline extent is exposed by the
erosion process; moreover, at some sites, the coast destruction rate achieves up to 1-3 meters a
year in natural conditions. Taking into account the technological impacts on the environment
that result from new areas development and global warming forecast for the XXI Century, the
coastal destruction rate must essentially increase.
In the case of pipeline deepening through rapidly retreating parts of the shore a risk of its
injury arises as a result of possible uncovering, whipping and mechanical deformations.
Pipeline deepening, landfilling and other protective measures are often ineffective, since not
only coastal bluff retreat towards the land, but also erosion of beach and offshore slope are
typical for rapidly destructing coastal sections. Besides, parts of the pipeline uncovered as a
result of erosion process may become subjected to direct dynamic impact of sea ice. Extrusion
of fast-ice on the shore results in ice bulk forming may be a cause of costal infrastructure and
pipeline destruction.
Thus, environmental safety of a pipeline may be provided by both a proper selection of the
most dynamically stable coastal zone and a design value of pipe deepening taking into account
forecasted coastal dynamics for the period of pipeline construction and exploitation.
Since 1988 Laboratory of Geoecology of the North, Faculty of Geography, MSU is
carrying out monitoring observations on the coastal dynamics in the area of the gas pipeline
underwater crossing. In the summer-autumn of 2005 regular cycle of coastal dynamics research
was performed. As a result reliable values of long-term erosion rates over a 17-years
observations period have been derived on Yamal as on Ural crossing sections.
In spite of short dynamic activity period coastal zone of Baydaratskaya Bay is
characterized by quite intensive lithodynamic processes, which is connected with relative wide
outlet to the south-western sector of Kara Sea on the one hand, and with low stability of the
coasts, composed of frozen dispersive sediments on the other hand.
Field investigations allow to estimate coastal stability of Yamal as on Ural sections in the
area of pipeline crossing. It was determined that the least stability is typical for coasts,
composed by clay sediments with high ice content and massive ice beds. Such coasts are wide
spread on the Ural section, including a coast directly within northern segment of cross-section.
Long-term erosion rates for these coasts can reach 2.0-2.5 m a year. Thereupon it is expedient to
shift cross-section on the Ural coast on 300-500 m to the east to the dynamically more stable
section. On the contrary, Yamal section is chosen correctly in respect to pipeline safety.
Values of coastal dynamics, achieved as a result of long-term monitoring, enabled to
estimate vertical deformation of the coastal zone profile for 30 years of the pipeline exploitation.