Vízügyi Közlemények, 1970 (52. évfolyam)

4. füzet - Rövidebb közlemények és beszámolók

discerned, namely uniform, non-uniform and un-steady conditions of flow, whereas in the case of sediment dynamics the two latter conditions coincide and only steady and un-steady conditions of sediment distribution can be considered. It should be noted that the latter is closely related to changes in the shape of the channel. Any change in sediment concentration is immediately followed by a change in channel shape and the latter is of direct influence on the velocity field of flow. On the other hand, any change in the velocity field is immediately reflected in the magnitude of the sediment transporting capacity. Consequently, no variations in concentration can be followed analytically, unless strictly defined boundary conditions are specified. However, boundary conditions can be approximated only, since the shape of the bounding surfaces is itself dependent on the changes in sediment concentration. It is thus seen that the only possible theoretical approach would consist of developing equations including the variations of the velocity field and concentration distribution together with the changes in the shape of boundary surfaces, in a manner that channel shape controls velocity field, velocity field the sediment distribution in the watercourse, while any change in sediment distribution changes the shape of the channel. Quite obviously, considerable difficulties are to be expected even when attempting a mathematical formulation of a similar problem. As is generally known even in the case of substantially simpler problems — e. g. the construction of the surface profile for un-steady, varied flow in fixed channels — the working assumption of a two-dimensional problem must be resorted to. This seems to be even more permissible for the much more complex problem under consideration, in that a steady discharge and varying velocities, with varying rates of solids transportation and a changing channel configuration is allowed for in the analysis, or even the variation of discharge is included. Having described the problem at hand and outlined in general the possibilities for a solution, the actually possible approaches will be reviewed. 1. Determination of the sediment carrying capacity of watercourses, formulation of equations describing the silting of reservoirs, solution of the equations In the theoretical formulation of sediment transporting capacity, the first major result is associated with the name of M. A. Welikhanov [26], who demonstrated that the diffusion theory of suspended sediment transportation [15, 4] failed to make allowance for the effect of solid particles on the velocity field, and introduced the concept of suspension work. This approach was further developed by A. N. Kolmogorov [21] and G. I. Barenblatt [16] by including the suspension work into the energy equation of turbulent pulsation. The set of equations developed by 70