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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.

The Ningxia reach of the Yellow River (NRYR) is wide and shallow, and instability and damages are likely to occur at its vulnerable zone. In this study, based on the one‐dimensional hydro‐sediment dynamics, two‐dimensional hydro‐sediment dynamics and vulnerable zone stability analysis model, a coupled model was established to analyze the scouring risk of the vulnerable zones in the NRYR during flood season. Considering the morphological change of bank slope at the vulnerable zones caused by flow erosion, the seepage stability of a typical spur dyke and protection embankment under the water level fluctuation conditions was analyzed. To fully reflect the coupled scouring effect of flow and sediment, the water flow scouring intensity index α is proposed. A significant increase of water flow scouring intensity index α will result in bank toe scouring, while its significant decrease will lead to silting of the bank toe. The probability of instability failure of the bank for the spur dyke slope is greater during the flood recession period. Compared with the influence of the change of river water level in the flood season, the slip stability of the bank slope is more sensitive to the change of bank toe erosion.

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