Академическое издательство «Гео»

Keywords: Baikal, erosion, accumulation, inundation, subaerial delta, hypsometric model.


Dynamics of the subaerial surface of the Selenga river delta

M.V. Pavlov*, E.A. Ilyicheva*, and L. A. Savelyeva**

*V. B. Sochava Institute of Geography SB RAS,
664033, Irkutsk, Ulan-Batorskaya str., 1, Russia, maksimpavlov_v@mail.ru, lenail3663@mail.ru
**St. Petersburg University, 199034, St. Petersburg, Universitetskaya emb., 7/9, Russia, savelieval@mail.ru

We investigated the changes in the subaerial surface of the Selenga river delta occurring under the effect of variations in the Lake Baikal level, erosion-accumulation activity, the river hydraulicity and, perhaps, due to tectonic processes. It is found that an increase in absolute elevations of the delta surface that began in 1956 was caused by multiple inundations of floodplains and terraces by the river waters at high-water periods. Bank outcrops with several horizons of buried soils were observed in the central part of the delta. A radiocarbon dating of horse bones and a pollen analysis of the profile of alluvial-delta deposits have been made. A retrospective analysis of topographic maps, nautical charts and space images is made. For a comparative analysis we generated hypsometric models, and the model of the evolution of erosion-accumulation processes. An assessment is made of changes in the area of the delta, the shoreline length, the lake percentage and the degree of channelization of the delta and its sectors. The findings can give evidence of the tectonic origin of a reduction in the area of the Sredneustyevskii sector on account of a compaction of waterlogged materials. Since 1956 the mean height of the delta surface has increased by 0.8 m as a result of an accumulation of alluvial deposits in the central part; the periphery of the delta continues to be inundated in the Sredneustyevskii sector to a depth of 0.5 to 1.5 m. The rate of erosion-accumulation processes is characterized on the basis of experimental observations. In the main delta arms, the rate of bank erosion is estimated as moderate: up to 3 m/year in the central part. The area at the head of the delta showed a high rate intensity of bank caving, 10 m/year or more. A reconfiguration of the channel network and formation of new bifurcation nodes and delta branches are taking place to date.

Keywords: Baikal, erosion, accumulation, inundation, subaerial delta, hypsometric model.

DOI: 10.21782/GiPR0206-1619-2016-5(128-136)