Vízügyi Közlemények, 1956 (38. évfolyam)
2. füzet - VII. Kisebb közlemények
(54) Ice Conditions and Shallows on Hungarian Rivers was read by K. Tory. Statistical data on ice conditions of the Hungarian Danube section are collected, and it is explained why there are no floods associated with ice — against the Danube — on the Tisza River. The second part of the paper deals with the investigation of shallows on the Upper Danube. Introduction of the concepts of the "top" shallow (the worst one at any time on a reach), of the depth deficit against the standard draught of 21 dm of a 1000ton barge, that is, the yardstick of the badness of the shallow has made possible to find a measure for the characterization of river sections from the viewpoint of navigation, whose variation in time reflects the success of river control work, or the harmful consequences of its neglect. (Full text, German and French summaries in this issue.) In the course of the discussion of the first two papers Prof. K. Debski (Warszava) pointed out that the results of investigations on the coefficient of channel stability is in perfect accord with his former calculations. E. Németh, Prof, of University, showed that the coefficients of channel stability suggested by Lohtin, Bogárdi and Dçbski are all quantities proportional to the reciprocal of the Froude number, which indicates that the laws of channel degeneration may perhaps be checked by model tests. He referred to investigations of H. House, M. Giandotti and J. B. Leighly on load transport and the distribution of the tractive force along the walls of regular trapezoidal profiles. Academician E. Xlosonyi found that the coefficient of channel stability express 's the ratio of average sediment grain size to tractive force. He drew attention to the fact that since in experiments on bed load motion not only the Froude number but also the Reynolds number plays a part, the scale effect has also to be taken account of. From contributions to the discussion by navigation and river control experts suggestions of Eng. S. Ilorvith (Danube Commission) are pointed out. From the viewpoint of river control he suggests the following research : 1. Investigition of water and sediment movement, of variations of surface slope, of the width of the band of sediment movement, of settlement deposits and shoal wandering, wear, disintegration and sorting of sediment, the operation of sediment measuring instruments, the variation of the coefficient of channel stability on two 21) km reaches of the Danube, to be selected for examination, one strongly unstable, the other in equilibrium. 2. Study of forecasting the expected shallow depths. 3. Freezing up of the river and formation of ice jams, in correlation with characteristic hydraulic data on the river. Forecasting ice events. III. Hydrographie Problems of Flood Control and Prevention The first paper entitled : Design Flood Stages of Hungarian Rivers, was read to the third session of the Congress by Z. Károlyi. Cand. of Technical Sc. In the past according to experience gathered during almost 100 years, the so far observed highest crest was taken for a design stage in reinforcing dams. This "empirical" flood stage was, where necessary (for instance in flood control of new areas), corrected partly on the basis of hydraulic calculations, partly by speculation. Recently flood stages of different probability are being calculated by methods of mathematical statistics. The principle of uniform safety can thus be realized, and levees can be reinforced economically. However, extrapolation has to be done very carefully, because the hydrologie applicability of Lhe different distribution functions is not sufficiently proved. Joint application of numerical and graphical methods is expedient, and for exceptionally critical reachcs the obtained results have to be checked against the physically possible maximum crest determined. Thereupon Doz. Dr. Ing. W. Lászlóffy read his paper on Development of Flood Forecasting in Hungary (Full text with German summary in this issue). The third paper was read by Prof. B. A. Marchinkov, representing the Bulgarian Academy of Sc., on :
