Hyperconcentrated flows as influenced by coupled wind-water processes |
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| Authors: | Email author" target="_blank">Jiongxin?XuEmail author |
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| Institution: | Institute of Geographical Sciences and Natural Resources Research, Chinese Academy of Sciences; Key Laboratory of Water Cycle and Related Land Surface Processes, Chinese Academy of Sciences, Beijing 100101, China |
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| Abstract: | Using data from more than 40 rivers in the middle Yellow River basin, a study has been made of the influence of coupled wind-water
processes on hyperconcentrated flows. A simple “vehicle” model has been proposed to describe hyperconcentrated flows. The
liquid phase of two-phase flows is a “vehicle”, in which coarse sediment particles are carried as solid-phase The formation
and characteristics of hyperconcentrated flows are closely related with the formation and characteristics of this liquid-phase
and solid-phase. Surface materials and geomorphic agents of the middle Yellow River basin form some patterns of combination,
which have deep influence on the formation and characteristics of liquid- and solid-phases of hyperconcentrated flows. The
combination of high percentages of relatively coarse material with low percentages of fine material appears in the area predominated
by the wind process, where the supply of relatively coarse sediment is sufficient, but the supply of relatively coarse sediment
is not. The combination of low percentages of relatively coarse material with high percentages of fine material appears in
the area predominated by the water process, where the supply of fine sediment is sufficient, but the supply of fine sediment
is not. In the area predominated by coupled wind-water processes appears the combination of medium percentages of coarse and
fine materials, and thus both coarse and fine sediments are in relatively sufficient supply. The manner in which the mean
annual sediment concentrations of liquid- and solid-phases vary with total suspended sediment concentration is different.
With the increased total suspended sediment concentration, mean annual sediment concentration of liquid-phase increased to
a limit and then remained constant; however, mean annual sediment concentrations of solid-phase increased continuously. Thus,
the magnitude of total suspended sediment concentration depends on the supply conditions of relatively coarse sediment and
the ability of the flow to carry these relatively coarse sediment particles. In the area predominated by wind process, both
the liquid- and the solid-phases cannot develop well, and their concentrations are low. In the area predominated by the water
process, the mean annual sediment concentrations of liquid- and solid-phases are also low. Only in the area predominated by
coupled wind-water processes, can the conditions most favor the development of both the liquid- and solid-phases, and then
the peaks of mean annual sediment concentrations of liquid- and solid-phases appear. Low values of suspended sediment concentrations
appear in the areas predominated by the wind process or by the water process, a fact indicating that the predominating wind
process or water process does not favor the development of hyperconcentrated flows. Peak values.appear in the area where the
coupled wind-water processes are predominated, indicating that the coupled wind-water processes most favor the development
of hyperconcentrated flows. |
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| Keywords: | river sediment hyperconcentrated flows liquid-solid two-phase flows wind process fluvial process Yellow River |
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