Vízügyi Közlemények, 1970 (52. évfolyam)

4. füzet - Rövidebb közlemények és beszámolók

Besides physical processes such of chemical character also occur in watercourses and mud flow. As a special case of these chemical processes, the occurrence and chemical alterations of a few disintegrating minerals (cassiterite, tungstenite, etc.) have been studied by S. Doucet [7]. The results reported in his paper may be helpful in solving a few special problems in sediment transportation and mineralogy. 2. Evaluation of observation results on sediment transportation Attempts at the determination of the characteristics of sediment transportation are made in order to utilize the information gained thereby in attaining specific goals. One of these goals is to predict the changes in bed morphology resulting from a particular regulation activity. When dealing with problems of similar nature it will be soon appreciated that if studies concerned with sediment transportation are to yield useful results for practice within a practically acceptable period of time and at a reasonable cost, predominantly inductive methods of research must be resorted to extensively. (In fact, there is increasing evidence available that the primarily deductive methods of research are usually of little practical value, owing partly to mathematical difficulties and partly to the relatively great number of unknown quantities and the great volume of observations required for their determination.) The application of largely (and of course not exclusively) inductive methods of approach to the solution of problems in river regulation is described in the paper of M. Miloradov [8]. Owing to adverse changes in water depths, regulation structures became necessary on the Beliyavitza section of the Danube between River Stations 1180 and 1185 km to ensure the required depths for navigation. The design of the structures was preceded by extensive observations on the movement of water, suspended sediment and bed-load over the section. The results of these were used to determine the characteristics of velocity distribution and transporting capacity. These characteristics were then used in constructing the mathematical model of bed changes for this particular section. Relationships of a form which proved difficult to handle mathematically were omitted from this model, including only the simpler mathematical expressions, which, however, were accurate enough for the problem. The structures were designed and constructed according to the computed results and subsequent checks on their performance verified the assumptions made in the design computations. An example for the application of predominantly inductive methods is illustrated also in the paper by J. Vincent [10], who performed observations in the model of the Danube section downstream of Bratislava. The model was built to 1 : 200 horizontal and 1 : 75 vertical scales and used to predict the influence of dredging operations on waterlevels — and especially highwater stages — over the section around Bratislava. The results obtained are very plausible: although the stages pertaining to particular discharges are lowered as a result of dredging, the 64