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THREE MAIN STAGES OF FLOODPLAIN EVOLUTION IN NORTHERN EURASIA AND THEIR ECOLOGICAL SIGNIFICANCEстатья Глава в книге
- Авторы: Sidorchuk Aleksey, Borisova Olga, Chernov Aleksey, Panin Andrey
- Сборник: Floodplains: Environmental Management, Restoration and Ecological Implications
- Серия: Environmental Research Advances
- Глава в коллективной монографии
- Год издания: 2013
- Место издания: Nova Science Pub Hauppauge, N.Y.,
- Первая страница: 69
- Последняя страница: 136
- Аннотация: Three main stages of floodplain formation were identified in northern Eurasia: (1) floodplain formation by the rivers larger than modern ones, (2) floodplain formation by the rivers smaller than modern ones, and (3) floodplain formation by the rivers of the modern morphological type. Large paleochannels of the first stage are common on river floodplains and low terraces on the East European and West Siberian plains. They are up to 10-15 times greater than modern river channels. The large paleochannels are dated to 11-15 thousand radiocarbon years B.P. (the Late Glacial time). The reconstructed surface runoff was then 1.4 times greater than the modern one on the northern mega-slope of the East European Plain, 2.3 times greater on its southern megaslope, and two times greater in West Siberia. Small oxbows of the second stage are wide spread on the floodplains of lowland rivers in Northern Eurasia, mostly in the forest zone. They were formed during the Atlantic period of the Holocene. During the Holocene climatic optimum, water runoff from the northern mega-slope of the East European Plain was ~180 km3 a-1, which is 30% less than the present-day runoff from the same drainage area. The annual runoff in the Volga River basin was ~134 km3, which is about one half of the present value. The runoff in the Don and Dnepr River basins during the Holocene optimum was 40% less, and that in the Ob’ and Irtysh River basin was 30% less than the modern one. The rivers of the present-day sizes and morphological types were formed during the climate cooling and wetting during the Subboreal and Subatlantic time of the Holocene, the general process being an increase in the river channel size and decrease in the width of meandering belt on the floodplain. The floodplain topography, formed during the previous stages, have significant influence on the modern flow hydraulics and the regime of sedimentation, being some kind of past events ‘memory’. Since the Holocene climatic optimum can be considered as a paleoanalogue of the global anthropogenic warming of the mid-21st century, information on the river floodplain evolution during the Late Glacial – Holocene can be used in the ecological scenarios of the global warming. The transformation of large lateglacial paleochannels into smaller ones due to climate warming at the beginning of the Holocene represents a likely scenario of the ecological changes within the present-day permafrost zone. The revers transformation of the modern rivers into smaller ones is a likely scenario of the ecological changes within the present-day forest zone. A general decrease in surface runoff may cause considerable landscape transformation in this vast territory.
- Добавил в систему: Сидорчук Алексей Юрьевич