Susceptibility of the Yuzhno-Sakhalinsk city territory to mudflows

The active development of the western macroslope of the Susunai range (deforestation, construction of a gas pipeline, ski slopes, slopes grading for various linear and permanent structures), as well the fact that the woody vegetation in the river basins rising in the Susunai range was partly damaged by windstorms, have led to the increase in dangerous exogenous geodynamic processes, including the debris flows. Thereby the susceptibility of the territory of the Yuzhno-Sakhalinsk urban district to debris flow processes was studied comprehensively.
For the area, a reconnaissance survey of the debris flow basins formed on the western macroslope of the Susunai range after a period of mass debris flows of 31.08–01.092023, was performed; signs and traces of debris flows were recorded, as well as individual parameters of debris flows based on direct signs. The initial data on the debris flow processes and forming factors within the studied area were collected and analyzed, such as archival and file materials, scientific publications, engineering survey materials, and field work results. During the field work on the studied territory a complex of natural and territorial conditions promoting the debris flows formation was identified, including geomorphologic, geological, hydrometeorologic, geobotanical and anthropogenic factors. The debris flow regime of the territory was revealed as a main scientific result of the work. Application of an instrumental method (measurements of a network of automatic precipitation meters) and analysis of the data obtained showed the absence of a pronounced altitudinal gradient of daily precipitation maxima. At the same time, the archival data confirm the dependence of precipitation amounts on the hypsometric levels for the longer observation periods, i.e. monthly and annual ones.
After completing a complex of field work, including instrumental measurements, and determining the natural and territorial conditions of debris flow formation and the debris flow regime of the territory, the data were processed in the laboratory and the main scientific and practical results were obtained. The parameters of the debris flow and the main dynamic characteristics of emerging debris flows were calculated based on the current technical standards. The debris flow-prone zones were identified and the address list of objects located in debris flow-prone zones was compiled.

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