Abstract
The paper provides a comprehensive assessment of channel formation conditions and hydrological-morphological characteristics, and also considers the features of the channel changes regime of parallel-braided channel reaches, being the most complex and diverse in morphodynamics. The general condition for their development is a large width of channels (respectively, the maximum value of the criterion of the flow quasi-uniformity suggested by I.F. Karasev). In such channels, the flow is divided into two branches, between which, in the middle of the channel, occurs accumulation of sediments and formation of mid-channel bars and islands. At the same time, parallel-braided channels are the result of other channel types (non-meandering) development due to certain changes in determining factors: increased water content and sediment runoff, overgrowth of channel bars, as a result of which mid-channel bars turn into islands, and anthropogenic impacts on rivers. On sandy floodplain rivers, parallel-braided reaches are typical for low-stable and unstable channels in the absence of the directed influence from bedrock banks on the flow and when effective water discharge passes over the floodplain edge. The islands in such braided reaches are mostly small. On rivers with incised channels, they are either similar in morphology and the channel changes regime to wide floodplain unstable channels, differing from the latter in large islands with elongated shape, or form sculptural islands and are very stable. In any variety, parallel-braided channels are very individual in their channel changes regime and there are no universal channel control schemes for them.
Highlights
Географический вестникГидрология Чалов Р.С., Беркович К.М., Рулёва С.Н., Завадский А.С., Головлёв П.П., Голубцов Б.Г
В статье даются разносторонняя оценка условий формирования, гидролого- морфологическая характеристика, рассматриваются особенности режима деформаций и трансформации самых сложных и разнообразных по морфодинамике параллельно-рукавных русловых разветвлений
The paper provides a comprehensive assessment of channel formation conditions and hydrological-morphological characteristics, and considers the features of the channel changes regime of parallel-braided channel reaches, being the most complex and diverse in morphodynamics
Summary
Гидрология Чалов Р.С., Беркович К.М., Рулёва С.Н., Завадский А.С., Головлёв П.П., Голубцов Б.Г. В ПРР обычно Lо/Bо > 4, составляя на Северной Двине 5,7, Мезени – 5.8, Печоре – 8,1 [14], верхней Оби – 4,2 [7], средней Лене – 4,8–4,9, нижней Оби – 6–10, увеличиваясь по мере повышения устойчивости русла. На верхней Оби и на средней Лене ПРР формируются элементарные и малые острова удлиненной формы из-за аккумуляции наносов посередине русла, развития кос в ухвостьях и их зарастания. На реках с врезанным руслом параллельно-рукавные разветвления либо аналогичны по морфологии и режиму деформаций широкопойменным неустойчивым, отличаясь от них большими размерами и удлинённостью островов, либо, встречаясь в скальных грунтах, формируя скульптурные и скульптурно-аккумулятивные острова и имея галечно-валунные руслообразующие наносы, являются очень устойчивыми.
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