On river geologic action and channel evolution of middle and lower Yangtze river

Dynamic forces of water in a river are the most active external factors to reform the bed and bank of the river, resulting in constant erosion, transportation, deposition of geologic bodies in the river valley, i.e. geologic action of the river. The river evolution and its geologic action are closely correlative, and the geologic action of a river is restricted by the geologic structure of the river valley. From the viewpoint of river valleys structure and rivers geologic action, the following respects are discussed:① The interaction between river flow and associated river bed and bank moulds the configuration of the river channel, the discharge, velocity vector and parttern of the river flow change with time and space, therefore the mode and intensity of the rivers geologic action also change, resulting in river evolution. ② The restraint of geologic structure of river bed and bank on the rivers geologic action controls the river evolution trend. ③ Investigating and analyzing the present conditions of the middle and lower reaches of the Yangtze river, it is probed into the relations of the river morphology with the geology structure of river bed and bank and with the rivers geologic action; probing into the characteristics and affecting factors of river channel evolution, it is purposed to recognize some rules of river channel evolution then find out the technology and method for macro control of river regime.