Abstract
Recently, construction of many large-scale water conservancy projects, as well as the vegetation protection and restoration projects in the upper reaches of the Yellow River, have led to serious changes in water inflow processes, sediment inflow processes, and scour and silting situation in the Ningxia section of the Yellow River (NSYR). This study explored the relationship between the sediment scouring and the silting law of the sediment-laden rivers and the equilibrium fluvial facies in the NSYR. The double cumulative curves of the annual silting amounts and annual incoming sediment amounts in the Qingtongxia–Shizuishan section were then established. It has been previously proven the fluvial facies coefficient increases year by year with the increase in the silting amounts in the watercourse, which lead to the evolution of the watercourse toward the wandering reach. The fluvial facies relationships of their cross-sections under an equilibrium state in the NSYR were established using a Yalin fluvial facies method. The Fr values under an equilibrium state and the actual state were analyzed. The results showed the Xiaheyan section was in an equilibrium state, and the Qingtongxia and Shizuishan cross-section were in a scouring state. This conclusion was confirmed by the actual measured results for numerous years.
Highlights
It is known that sediment scouring and silting in natural sediment-laden rivers, along with the adjustments of the riverbed morphology, are closely related to the water and sediment conditions [1,2]
In the present study, based on the data obtained from the three main hydrological stations in the Ningxia section of the Yellow River from 1950 to 2010, the variation process curves for the runoff and sediment discharge of the Xiaheyan hydrological stations during both flood seasons and non-flood seasons were established, as detailed in Figures 2 and 3
51 silt measurement cross-sections were arranged in the Ningxia section in 1993, 1999, 2001, and 2009, respectively; 22 cross-sections were arranged at the end of the section located from Xiaheyan to the Qingtongxia Reservoir, and 29 cross-sections were arranged in the section from Qingtongxia to the Shizuishan Yellow River Bridge
Summary
It is known that sediment scouring and silting in natural sediment-laden rivers, along with the adjustments of the riverbed morphology, are closely related to the water and sediment conditions [1,2]. The total amount of sediment entering the Yellow River decreased; the main channel and branches of the river experienced frequent rising and falling actions, and the relationship between the water and sediment remained uncoordinated These factors had resulted in imbalance conditions between the sediment scour, silting, and river regime evolution in the Ningxia River Reach area [3,4]. The examination of the river facies relationships of the Yellow River in Ningxia and Inner Mongolia can potentially reveal the evolution processes of a “balance-destruction-rebalance” cycle in these areas of the river It is of great theoretical and practical significance that a thorough understanding of the river bed morphology of alluvial rivers is established to carry out accurate hydraulic calculations of these alluvial rivers and formulate effective river regulation plans
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