PSI - Issue 20
S.A. Tikhonova et al. / Procedia Structural Integrity 20 (2019) 230–235 S.A. Tikhonova et al. / Structural Integrity Procedia 00 (2019) 000 – 000
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Dependence of vegetation index and meteorological factors was also investigated: average monthly air temperature, average monthly amount of precipitation in the studied areas. NDVI trends show a correlation with surface air temperature and total precipitation. With an increase in air temperature and a decrease in precipitation, the values of vegetation index decrease both on the main and background areas (2006, 2015). As the amount of precipitation increases, NDVI values increase (Fig.2). Site № 2 refers to the first stage of pipeline construction; in 2007 – 2008, the construction period was accompanied by activation of geocryological processes, water logging of the site, as evidenced by ground monitoring data, as well as a noticeable decrease in NDVI value. In 2014, permafrost processes fade out, as a result of protective measures taken by operating organization. Based on different types of vegetation, analysis of vegetation index values and ground monitoring data, a table for ranking vegetation status by NDVI value for two groups of plots was constructed for selected areas. Using NDVI, it is possible to assess the impact of the pipeline on activating geocryological processes, as well as to rank the sections of underground pipeline route, according to the degree of change in vegetation cover.
Fig.2. Graphs of changes in NDVI, temperature and amount of precipitation in the area № I near the town of Lensk
Table 3. Evaluation of the state of vegetation by NDVI for group 1 (Lensk, and p. Vitim). 0,40 and more Normal vegetation 0,35-0,40 Sparse vegetation 0,30-0,35 Oppressed vegetation 0,30 and less Severely depressed vegetation Table 4. Assessment of the state of vegetation by NDVI for group 2 (Neryungri) 0,30 and more Normal vegetation 0,25-0,30 Sparse vegetation 0,20-0,25 Oppressed vegetation 0,20 and less Severely depressed vegetation
4. Conclusion Our results have demonstrated the prospects of using NDVI vegetation index in studies of complex interactions between the environment, permafrost and underground oil pipelines based on remote sensing products. Despite the fact that increase in average annual air temperature and average annual precipitation also affects the change in vegetation index, using NDVI it is possible to assess the impact of pipeline on activating geocryological processes, as well as rank the sections of underground pipeline according to the degree of change in vegetation.
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