THE SLOPE DEBRIS BASINS ON MARINE TERRACES OF THE SAKHALIN ISLAND AND THEIR DEPENDENCE ON THE LITHOLOGICAL COMPOSITION OF ROCKS

S. V. Rybal’chenko^a,# and K. V. Verkhovov^a,##

^aFar East Geological Institute, Far East Branch, Russian Academy of Science, Sakhalin Department, Yuzhno-Sakhalinsk, Russia
^bMPI Capital construction management, Yuzhno-Sakhalinsk, Russia
^#E-mail: rybalchenko_sv@mail.ru
^##E-mail: konstantin_verhovov@mail.ru

On Sakhalin, a significant portion of settlements and objects of transport infrastructure are located in the coastal zone and are often influenced by the slope geodynamic processes (landslides, debris flows, etc.), which are not taken into account in territorial planning and tracking. At first glance, the relatively resistant rocks are more susceptible to factors of denudation, and the motley composition of the sweet, forming the marine terraces, creates severe engineering geological conditions. The most dangerous geodynamic processes on the slopes of the marine terraces of the Sakhalin island are debris flows, because they are distinguished by suddenness, high speed, throw and a great destructive force, even with small amounts. Geological factors is one of the determinants in debris flow formation; and the lithological composition of the rocks affects the characteristics of debris flows, debris flow catchments, and debris flow process in general. This paper examines the influence of lithological composition on the forms of slope debris flow catchments, and the type of debris flow process. Lithological complexes of rocks are distinguished on the basis of stability of species to the factors of denudation. Thus, lithological complexes unite rocks composing a suite of similar genesis and physical properties regardless of their age. The mineralogical composition of the cement and grain-size composition of rocks exerts the greatest effect on the resistance of rocks to denudation factors. Each of the lithological complexes is represented by debris flow-forming rocks of specific composition, which controls the shape features and geomorphological structure of debris flow catchment, debris flow and the process in general. There is a direct correlation: lithologic complex - debris flow process – shape of the debris flow catchments. On the slopes of the marine terraces of Sakhalin it is possible to identify six types of slope debris flow catchments: a potential debris flow origination site, a gully, a landslide funnel, a linear, sinuous and diamond-shaped ravine. Shape of slope debris flow catchments may be complicated by additional elements of erosion landforms; however, form and formula of the main morphometric catchment allows us to determine the shape of the entire debris flow catchments, type of debris flow process and lithological complex.

Key words: denudation, lithological complex, debris flow, slope debris flow basin, debris flow process

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