INVESTIGATION OF FORMATION CONDITIONS AND COMPUTATIONS OF MAXIMUM WATER LEVELS ON THE LENA RIVER NEAR THE TOWN OF LENSK

A. V. Rozhdestvenskii, V. A. Buzin, and V. A. Lobanov

Catastrophic floods on the Lena River near the town of Lensk in 1998 and especially in 2001 result in the necessity of a detailed investigation of causes and conditions of formation of similar extreme phenomena and of the improvement of calculated values of maximum water levels. Genesis of formation of peak levels during spring floods in the form of two waves related to ice dams and the free state of the channel is considered. Meteorological conditions leading to the formation of dam levels are analyzed in light of modern climate changes. Series of the observational data on the maximum water levels at Lensk are reduced to a long-term period, and their homogeneity and stationarity are tested. With consideration for the extreme historical level of 1878, the maximum water levels are recalculated with 1% probability. The mark resulted from these calculations is equal to 171.87 m of BS (Baltic System), which is 1.8 m higher than that taken earlier for design.

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