Possibility and Restrictive Factors of High Efficiency Transport of Hyper Concentration Floods in the Lower Yellow River

Sediment transport in the lower reaches of the Yellow River has always been a major topic in river management in China. With the rapid economic development, the availability of water resources has become one of the constraints affecting the regional economic development of the Yellow River Basin. In order to meet the requirements that less water could own greater sediment transport capacity, and to save water resources to ensure the basic health of the Yellow River, more efficient mode of sediment transport has become an important research objective in the study of the Yellow River. In view of the history of the Yellow River, there have been hyper concentration floods under the condition of channel scouring. Considering the powerful sediment transport capacity of hyper concentration floods, we study the possibility of adopting hyper concentration floods mode to transport plenty of sediment in the lower reaches of the Yellow River, and make a quantitative analysis of the critical conditions of hyper concentration flow to achieve the equilibrium of scouring and silting and even the state of channel scouring. Quantitative calculation was carried out at the Huayuankou section and Lijin section, and the variation of relative sediment transport capacity was taken as the main physical quantity to carry out the analysis and comparison under different water and sand conditions. The results show that the hyper concentration floods under natural conditions in the balance of scouring and silting have certain particularities, especially the relationship between gradation and sediment concentration might satisfy the double logarithmic equation after exchanging of suspended sediment and bed sediment along the river. At the same time, the conditions of hyper concentration floods with different sediment sources have certain rules for the efficient sediment transport mode with some differences. Finally, we put forward an index map to define different types of hyper concentration floods, for elaborating essential differences between scouring type and silting type of flood with high sediment concentration.