An understanding of the characteristics of fluvial erosion and deposition is essential for the proper solution of problems related to hydropower and bridge construction, the improvement of inland waterways, agricultural land reclamation, and many other practical tasks. At the same time, any general theory of the development of the geographical environment must take into account the activity of flowing water, since it continuously transforms the landscape. The theory of erosion-deposition and channel processes, as a branch of hydrology, is also studied within several technical disciplines, including hydraulic engineering, hydraulics, and engineering geology, as well as within natural-science disciplines such as physical geography and geomorphology. The foundations of this field were established both by engineers (F. M. Lokhtin and N. S. Lelyavsky) and by specialists in the natural sciences (V. V. Dokuchaev, A. P. Pavlov, I. D. Chersky, and S. N. Nikitin). These two directions, the engineering and the natural-historical approaches, subsequently underwent substantial development and specialization. Today, an enormous body of empirical material has been accumulated, making it possible to identify a series of specific regularities. However, integrating these regularities into a unified system is possible only when flowing water is regarded as an integral component of the geographical environment. Flowing water develops under specific conditions, and the combination of these conditions determines the volume and dynamics of discharge, the average longitudinal gradient, the grain size and mineral composition of alluvial sediments, and, in short, all the principal factors governing the intensity and characteristics of channel-forming activity. It follows that erosion-deposition and channel processes cannot be viewed as an isolated chain of phenomena developing independently of the geographical environment and without regard to the specific features of the drainage-basin landscape. Flowing water and its drainage basin must be considered together as closely interconnected and mutually dependent entities. These principles determine the structure of the present study. First, rivers are examined as elements of the geographical environment and as components of the continental hydrological network. Second, the fundamental characteristics of erosion-deposition and channel processes are established. Finally, several of the most typical manifestations of channel processes are described. In certain sections of the subject under consideration, such as channel processes in mountain rivers and the zonality of channel processes, the available data are insufficient and therefore only permit the formulation of problems rather than their complete resolution. Consequently, this work does not seek to provide an exhaustive and systematic treatment of the entire field.