Research on the Influence of Flow-sediment Variation on Cross-section Configuration Change in Ningxia-Inner Mongolia Reach of the Yellow River

The adjustment process of river section shape is an adaptive process to the change of incoming water and sediment conditions, which can reflect the evolution process of river erosion and deposition to a certain extent. Based on the observed data from 1965 to 2004 at various hydrological stations in the upper reaches of the Yellow River, this paper analyzes the adjustment process of the river section and its internal relationship with the variation of water and sediment conditions in the Ning-Meng reach. and puts forward the response relationship between the process of water and sediment inflow and the morphological characteristics of the river section in the Ning-Meng reach, which provides a basis for the study of river regulation in the Ning-Meng reach. The results show that, the typical cross-section changes have the trend of the bank-full area decreased and the width-depth ratio increased year by year, and increase bank-full area were increased with the water of the year; but each section of each period increased in different degree, before 1986,each section significantly increased; after 1986, the Ningxia reach increased less, but the Inner Mongolia reach increased greatly; the width-depth ratio enlarged with the increase of incoming sediment coefficient, the increasing trend of the Ningxia reach was not obvious, but the increasing trend of the Inner Mongolia reach before 1986 was no more obvious than after 1986. Therefore, the Cross-section configuration changes of Ningxia reach were relatively small and tended to be stable; but the Cross-section configuration of Inner Mongolia reach become more and more wide and shallow with the increase of incoming sediment coefficient. The critical water sediment boundary conditions of the Cross-section configuration of Ningxia-Inner Mongolia Reach tending to be stable were obtained by analysis of the response relationship between the sediment delivery ratio and the conditions of incoming water and sediment.

Key words: The Yellow River；Ningxia-Inner Mongolia reach；The bank-full area；The width-depth ratio；Sediment delivery ratio