Formation of riverbed sediments in the upper reaches of rivers originating from glaciers (on the example of River Aktru, Altai Mountains)

A. M. Tarbeeva; N. N. Vinogradova; I. V. Krylenko; V. V. Surkov

doi:10.7868/S0435428118040065

Formation of riverbed sediments in the upper reaches of rivers originating from glaciers (on the example of River Aktru, Altai Mountains)

A. M. Tarbeeva, N. N. Vinogradova, I. V. Krylenko, V. V. Surkov

https://doi.org/10.7868/S0435428118040065

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Abstract

The changes in the composition of river sediments of River Aktru (the North-Chuyskiy Ridge) in the first 8 km downstream from its source from the glaciers are discussed. The glaciers are retreating and the length of the river network increases due to the formation of new river channels. Study of river sediment was carried out by direct measurements of grain size composition and morphology of debris on 18 test sites. It was revealed that the Altai rivers, as well as the previously studied rivers in the Elbrus region (Caucasus Mountains), maybe divided into the altitudinal zones that differ in the duration and conditions of river channel and sediment formation. Primary riverbeds with high stream gradients and channels with waterfalls and rapids, passively fitting to the roughness of the moraine terrain are formed in the periglacial zone. Channels are covered by badly sorted and badly rounded sediments of large size. The upstream zone (zone of active exogenous processes) is characterized by decreasing stream gradients and step-like longitudinal profiles of channels. Power flow increases and helps to activate the transport of sediment and the intensity of their reworking. River sediments in channels are formed largely as a result of processing of fluvio-glacial and alluvial- mud flow deposits. Average diameter of sediment particles reduces, their roundness strongly increases. Due to the peculiarities of the climate, topography and geological structure, the Altai rivers compared with rivers in Elbrus region are characterized by smaller stream gradients, less impact of mudflows, smaller size of river sediment grains and the bigger length of the periglacial zone.

Keywords

mountain rivers, glacier retreat, river sediments, Altai Mountains, the river Aktru

About the Authors

A. M. Tarbeeva

Lomonosov Moscow State University
Russian Federation
Faculty of Geography

N. N. Vinogradova

Lomonosov Moscow State University
Russian Federation
Faculty of Geography

I. V. Krylenko

Lomonosov Moscow State University
Russian Federation
Faculty of Geography

V. V. Surkov

Lomonosov Moscow State University
Russian Federation
Faculty of Geography

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Review

For citations:

Tarbeeva A.M., Vinogradova N.N., Krylenko I.V., Surkov V.V. Formation of riverbed sediments in the upper reaches of rivers originating from glaciers (on the example of River Aktru, Altai Mountains). Geomorfologiya. 2018;(4):69-79. (In Russ.) https://doi.org/10.7868/S0435428118040065