This is a comparative analysis of snowmelt flood extension within the area in the Middle Lena from Pokrovsk gauging station to Namtsy one in case of ice jamming which comes with formation of the highest historical water levels in 1958 and 2010. The change in water surface slope and the rate of increase and decrease of the water level at the analyzed gauging stations has been shown. It is revealed that it is necessary to conduct a research of conditions of ice jamming during spring ice drift in order to establish the measures to realize flood prevention. Comparison of conditions and processes of formation of maximum water levels of spring flood in the years under review is of considerable scientific interest because in 2010, in contrast to 1958, on the considered section of the Lena river there were major changes of anthropogenic nature: the transformation of the river bed and measures to weaken the ice cover in order to reduce the probability of ice congestion. The paper concludes that a much larger increase in water level in 2010 is likely to be caused by anthropogenic factor. The intensity of change in the highest water-surface elevations and water-surface slopes as measured at the stream gaging stations covered, at periods when the Lena River ice breaks up with ice jams created depends on the change in the characteristics of the river’s morphology and the hydrological processes that affect the dynamics of the ice jams formation and breaking-up at the Lena River. In 2010, the highest ever recorded water level rising speed (119 cm/h) and the greatest ever water-surface slope (18.04·10-5) were registered at the section of the river between the Kangalassy and the Namtsy gaging stations. At the section of the Lena River between Pokrovsk and Namtsy, the seasonal high water expands unevenly when spring ice drifts occur. Therefore, the emergency and rescue action taken may fail to be effective. Thus, in order to have effective action in place to successfully prevent floods, the arrangements need to be sped up for the research to be held to study and understand the conditions causing ice jams to be created when spring ice drifts occur so that the flood prevention practices (methods) could be developed for the most typical sections throughout the Middle Lena River.

Ammosov Alexander Prokopievich, Doctor of Science (Technical), Professor 

Shpakova Raisa Nikolaevna, Candidate of Sciences (Geography), Moscow State Institute of International Relations (MGIMO), 76 (bldg. 1), Prospect Vernadskiy, Moscow, 119454, Russian Federation, tel.: 8(919)7656811, е-mail: production2003@mail.ru 

Kusatov Konstantin Innokentievich, Senior Hydrologist, Department of Hydrological Forecasts Yakutia Hydrometeorology and Environment Control Office, 8, Ya. Potapov st., Yakutsk, 677010, Russian Federation, tel.: 8(4112)36-02-28, е-mail: 360228@maill.ru 

Kornilova Zoya Grigorievna, Candidate of Science (Technical), Larionov Institute of Physical and Technical Problems of the North SB RAS, 1, Oktyabr’skaya st., Yakutsk, 677891, Russian Federation, tel.: 8(4112)39-06-71, е-mail: zoyz_korn@mail.ru

Ammosov A.P., Shpakova R.N., Kusatov K.I., Kornilova Z.G. Changes in Water Levels and Water Surface Slopes in Case of Congestion on the Lena River. The Bulletin of Irkutsk State University. Series Earth Sciences, 2019, vol. 28, pp. 3-20. https://doi.org/10.26516/2073-3402.2019.28.3 (in Russian)

Kusatov K.I., Аmmosov А.P., Kornilova Z.G., SHpakova R.N. Аntropogennyj faktor v zatoroobrazovanii i vesennem navodnenii pri ledokhode na r. Lena [Anthropogenic factor in ice formation and spring flooding at the Lena river]. Meteorologiya i gidrologiya, 2012, no. 6, pp. 54-60. https://doi.org/10.3103/S1068373912060064. (in Russian)

Buzin V.А. Zatory l'da i zatornye navodneniya na rekakh [Ice jams and congestion on the rivers]. Saint-Peterburg, Gidrometeoizdat Publ., 2004, 203 p. (in Russian)

Buzin V.A., Goroshkova N.I., Strizhenok A.V. Maksimalnye zatornye urovni vody severnyh rek Rossii v usloviyah izmeneniya klimata i antropogennogo vozdejstviya na process zatoroobrazovaniya. Meteorologiya i gidrologiya, 2014, no. 12, pp. 55-61. (in Russian)

Kil'myaninov V.V. Аnaliz uslovij formirovaniya i dolgosrochnyj prognoz zatornykh urovnej na r. Lene [Analysis of formation conditions and long-term prognosis of congestion levels on the Lena river]. Meteorologiya i gidrologiya. 1992, no. 4, pp. 82-89. (in Russian)

Kil'myaninov V.V. Vliyanie meteorologicheskih uslovij pered nachalom ledohoda na masshtab zatornyh navodnenij na r. Lena. Meteorologiya i gidrologiya, 2012, no. 4, pp. 86-89. (in Russian)

Kil'myaninov V.V., Tazatinov V.M., SHepelev V.V. Zatory – ledovye monstry rek YAkutii [Congestion – the ice monsters of the rivers of Yakutia]. Nauka i tekhnika v YAkutii, 2001, no. 1, pp. 36-40. (in Russian)

Kusatov K.I. Srezki zatornykh urovnej vody [Cutting of mastic water levels]. Meteorologiya i gidrologiya, 1977, no. 10, pp. 113-116. (in Russian)

Mostakhov S.E. Reka Lena [Lena river]. Yakutsk, YAkutskoe knizhnoe izdatelstvo Publ., 1972, 142 p. (in Russian)

Nogovicyn D.D., Kil'myaninov V.V. K voprosu o prognozirovanii zatornyh yavlenij na r. Lene [On the prediction of congestion on the Lena river]. Nauka i tekhnika v Yakutii, 2007, no. 1(12), pp. 19-24. (in Russian)

Volkova L.S., Gnatyuk G.A., Dektyarev A.G. [et al.]. Respublika Saha (YAkutiya). Kompleksnyj atlas [The Republic of Sakha (Yakutia). Comprehensive Atlas]. Yakutsk, FGUP YAkutskoe aehrogeodezicheskoe predpriyatie Publ., 2009, 239 p. (in Russian)

Rozhdestvenskij A.V., Buzin V.A., SHalashina T.L. Usloviya formirovaniya i veroyatnye znacheniya naivysshih urovnej vody r. Lena u g. Yakutsk. Meteorologiya i gidrologiya, 2010, no. 1, pp. 77-87.

Uhov G.A., Kil'myaninov V.V. Zatornye yavleniya na rekah Lenskogo bassejna [Congestion on the rivers of the Lena basin]. Sibirskij nauchnyj vestnik, Novosibirsk, 1999, is. 3, pp. 198-211. (in Russian)

Resursy poverhnostnyh vod SSSR. T. 17. Leno-Indigirskij rajon [Surface water resources of the USSR. Vol. 17. The Lena-Indigirka district]. Leningrad, Gidrometeoizdat Publ., 1972, 652 p. (in Russian)

Beltaos, S., Carter, T., Rowsell, R., DePalma Sarah G.S. Erosion potential of dynamic ice breakup in Lower Athabasca River. Part I: Field measurements and initial quantification. Cold Regions Science and Technology, 2018, vol. 149, pp. 16-28. https://doi.org/10.1016/j.coldregions.2018.01.013

Gautier E., Dépret Th., Costard F., Virmoux C., Fedorov A., Grancher D., Konstantinov P., Brunstein D. Going with the flow: Hydrologic response of middle Lena River (Siberia) to the climate variability and change. Journal of Hydrology, 2018, 557, pp. 475-488 https://doi.org/10.1016/j.jhydrol.2017.12.034.

Hiyama T., Takakura H. (eds.). Global Warming and Human – Nature Dimension in Northern Eurasia, Global Environmental Studies. https://doi.org/10.1007/978-981-10-4648-3_3

Jomelli V., Favier V., Vuille M., Braucher R., L. Martin Blard, P.-H., Colose C., Brunstein D., He F., Khodri M., Bourle`s D.L., Leanni L., Rinterknecht V., Grancher D., Francou B., Ceballos J.L., Fonseca H., Liu Z., Otto-Bliesner B.L. A major advance of tropical Andean glaciers during the Antarctic cold reversal. https://doi.org/10.1038/nature13546.

Kovachis N., Burrell B.C., Huokuna M., Beltaos S., Turcotte B., Jasek M. Ice-jam flood delineation: Challenges and research needs. Canadian Water Resources Journal. Revue canadienne des ressources hydriques. http://dx.doi.org/10.1080/07011784.2017.1294998.

Lindenschmidt K.-E., Huokuna M., Burrell B.C., Beltaos S. Lessons learned from past ice-jam floods concerning the challenges of flood mapping. International Journal of River Basin Management. https://doi.org/10.1080/15715124.2018.1439496.

Lindenschmidt K.-E., Das А., Rokaya Pr., Chu T. Ice-jam flood risk assessment and mapping. Hydrol. Process, 2016, 30, 3754-3769. https://doi.org/10.1002/hyp.10853.

Rawlins M.A., Ye H., Yang D., Shiklomanov A., McDonald K.C. Divergence in seasonal hydrology across northern Eurasia: Emerging trends and water cycle linkages. J. Geophys. Res. 114, D18119 [Electronic resource]. https://doi.org/10.1029/2009JD011747.

Suzuki L.K., Matsuo K., Yamazaki D., Ichii K., Iijima Y. Papa, F., Yanagi L.Y., Hiyama T. Hydrological Variability and Changes in the Arctic Circumpolar Tundra and the Three Largest Pan-Arctic River Basins from 2002 to 2016 [Electronic resource]. Remote Sens, 2018, no. 10, 402 p. https://doi.org/10.3390/rs10030402.