Академическое издательство «Гео»

Keywords: slope wash, gully erosion, suspended sediment yield, ponds, sediment balance in the basin.


The functioning of the cascade lithodynamic system of the Kuda river basin (Upper Angara region)

S.A. Tukhta*, O.I. Bazhenova*, **, Yu.V. Ryzhov*, **, ***

*V.B. Sochava Institute of Geography, Siberian Branch, Russian Academy of Sciences, 664033, Irkutsk,
ul. Ulan-Batorskaya, 1, Russia, varitan@ya.ru, bazhenova@irigs.irk.ru, ryzhovyurij@yandex.ru
**Irkutsk Scientific Center, 664033, Irkutsk, ul. Lermontova, 134, Russia,
bazhenova@irigs.irk.ru, ryzhovyurij@yandex.ru
***Institute of the Earth’s Crust, Siberian Branch, Russian Academy of Sciences,
664033, Irkutsk, ul. Lermontova, 128, Russia, ryzhovyurij@yandex.ru

The redistribution of sediments in the Kuda river basin as a result of erosion-accumulation processes is investigated from the systems perspective. The current geodynamic position of the basin associated with the transition zone from the Siberian platform to the Baikal rift is emphasized. The contribution of cryogenic, karst and aeolian processes to the mobilization of matter in the system is considered. A quantitative assessment of the amount of transported material in the upper (slope), middle (ravine) and lower (riverbed) lithodynamic zones of the basin was made. Time series of the main hydroclimatic indicators were used to determine the long-term dynamics of the functioning of the basin. Using the satellite images, we identified changes in the economic activities within the basin over the past 30 years. They imply a reduction in croplands and an expansion of grasslands. Calculations show that the annual volume of sediments transported within the basin reaches 3 184 430 tons. Most of them (89 %) are involved in the movement by the runoff of storm water, and only 364 405 tons are transported with the runoff of melt water. The role of gully erosion in ablation and sediment transportation is insignificant, because most of the gullies are inactive with a reduction in agriculture; the average growth rate of the heads of gullies does not exceed 0.5 m/year. Channel processes contribute primarily to the redistribution of sediments between adjacent sections of the channel, and their transport to large distances is limited by karst processes and by a significant anthropogenic transformation of the bottoms of the valleys. The annual flow of suspended and transported sediments is a mere 31 000 tons, and the main ablation of material from the system occurs in a dissolved form. In general, the mechanical volume of sediment yield from the system makes up 1 %. The rest of material is redistributed in the basin and causes an enhanced accumulation. It is shown that almost half of the sediments is intercepted by large ponds; the rest is accumulated in the bottoms of the valleys in areas with active karst development, on floodplains as well as in talus and proluvial trains. The study determined a general trend in the transformation of the relief as a result of the functioning of the basin implying its planation.

Keywords: slope wash, gully erosion, suspended sediment yield, ponds, sediment balance in the basin.

DOI: 10.21782/GiPR0206-1619-2019-2(147-158)