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The alluvial river flooding problem in Inner Mongolia is prominent along the upper reaches of the Yellow River. Studying the scour and silting evolution of the river and the response mechanism of the floods can provide technical support for flood prevention and disaster mitigation in this river section. According to data on ice flood and scour and silting evolution, this paper produces the response relationship between a scour and silting evolution characteristics indicator and an ice flood condition change representation indicator based on formulaic calculations and related analyses. The results show that bankfull discharge, a characteristic indicator of river scour and siltation evolution, is closely related to the characterization indicators for ice flood sub-ice flow capacity and trough water storage increment. The under-ice flow capacity is about 1/5 that of bankfull discharge, and it decreases as bankfull discharge decreases. In addition, the channel detention increment increases as bankfull discharge decreases. The safety flow capacity in the main channel for ice flood control should not be less than 2 000 m³/s, and the increment in water storage should be kept below 1.4 billion m³ in the reach. The preliminary results can serve as a major guide for ice flood control in Inner Mongolian reaches. [ABSTRACT FROM AUTHOR]

Health of a river mainly depends on water demand for channel forming and sediment transport, particularly on the rational allocation of water resources in alluvial river. In this paper, energy balance equation was used to investigate the energy dissipation of sediment-carrying water flow, and distribution mode for water flow channel forming and sediment-carrying energy in the Upper Reaches of Yellow River in Inner Mongolia. Energy dissipated in alluvial river can be divided into two parts: one is to form a certain scale of river channel against boundary resistance of riverbed; another for transporting sediment. Silting or scouring of the riverbed during transportation can be an inherent indicator for the energy balance of water flow. Combined with the characteristics of flow and sediment movement in alluvial rivers, a complex relationship was proposed including the bank full discharge, the incoming sediment load, and the amount of scour and silting, in order to determine the water demand for channel forming and sediment transport. A calculation method was used to present the water demand for channel forming and sediment transport in a state of scour and silting in alluvial river. A calculation equation of water demand for channel forming and sediment transport was also established based on the measured data of the Inner Mongolia Reaches from 1960 to 2013. The calculated results showed that the incoming sediment load into the Inner Mongolia reaches was 70-110 million tons in flood season, and the water demand required for channel forming and sediment transport was 9.46-14.12 billion m³, providing that the silting ratio in these reaches was controlled below 30%, and a median water river channel in a scale of 2 000-3 000 m³/s. The water demand for channel forming and sediment transport mainly depends on incoming sediment loads, scales of river channels, and various levels of silting. In the case of the water demand higher required for channel forming and sediment transport, three trends can be obtained, including that, 1) the silting ratio can be lower control in an incoming sediment load and same scale of median water river channel; 2) the scale of median water river channel can be larger in an incoming sediment load and same silting ratio controlled, and 3) the incoming sediment load in flood season can be higher in the same silting ratio controlled and requirement on scale of median water river channel. There was agreement with the calculation results and the variation law of the water demand for channel forming and sediment transport of the Inner Mongolia reach, and the energy dissipation of alluvial rivers as well. The change law of water demand was obtained for channel forming and sediment transport under various conditions of sediment level, river channel scales and siltation levels. The findings can provide a sound technical support for the regulation of water resources in the Upper Reaches of Yellow River in Inner Mongolia. [ABSTRACT FROM AUTHOR]