EVALUATION OF NATURAL RISK CHANGES WITHIN EROSIONAL THERMOKARST PLAINS UNDER THE IMPACT OF CLIMATIC TRENDS

The relevance of assessing risk to engineering structures from geohazards is determined by changing natural conditions in the permafrost zone. Risk assessment by statistical methods directly is accompanied by certain difficulties. Accumulation of statistics requires a significant amount of time, and this time is often comparable to the time of engineering structure operation. The most difficult stage of risk assessment is the assessment of the probability of damage to engineering structures caused by a hazardous geological process. The aim of the study was to substantiate the method for solving this problem on the territory of thermokarst plains with fluvial erosion for linear engineering structures using the methods of mathematical landscape morphology. Mathematical landscape morphology allows us to proceed to the quantitative risk assessment. The first step of applying methods of mathematical landscape morphology is to divide the area into homogenous by the process development sections. The method is based on the model that was proposed by the authors for the development of the morphological structure of thermokarst plains with fluvial erosion under conditions of an asynchronous start, which is realized according to empirical verification in most of cases. The model of risk assessment was applied to 4 key areas located under different physico-geographical conditions, but having morphological homogeneity. Using satellite images of different periods, the delineation of thermokarst lakes and khasyreys was carried out. The average density of the number of lesions in different areas varies from 0.00026 year^–1 to 0.00104 year^–1, and there is no clear trend of change with time. According to quantitative experimental data, there has been a site-differentiated change in the risk of damage to linear structures within the thermokarst plains with fluvial erosion over the past few decades (46–56 years). The probability of damage to linear engineering structures has changed significantly in plot 35 (Yano-Indigirskaya lowland), which confirms the chi-square test. The probability of defeat increased by 6–9 times according to the estimates obtained. This situation is observed when the lengths of linear structures are 3–4 km. However, in most of the key areas, there is no significant change in the probability of damage, despite ongoing climate change.