Based on the researches of the field data of the Lower Yellow River,the inter-effects between channel geometry and flow and sediment transport have been analysed and two patterns of scour-fill changes in river bends and straight reaches have been suggested.The effects of channel geometry on flow and sediment transport could be estimated through the following eqationsin which are usually not equal to unity,The narrower the cross-section is,the higher the values of β and α.The role of flow and sediment transport on cross section could be considered by eqs.(27) to (30).