Vízügyi Közlemények, 1958 (40. évfolyam)

4. füzet - VII. Kisebb közleménye

(84) the series of stage data for the Mezőtúr gaging section of the Körön River — where records are kept since 1950 only — on basis of data observed at a gaging station more upstream (Fig. 9). Periods when the stage in the Körös River exceeds that in the Hortobágy Canal could be determined directly by comparing the two series of stage data (both indicating elevations above Adriatic level) in Fig 10. It has been assumed that the flood gate is closed at the beginning of each major flood. Stages in the two water-courses rise independently from this moment as long as the stage in the Hortobágy Canal attains the usually receeding one in the Körös River. The flood gate is opened when the two stages become equal. The „opening stage" has been determined by summing up the flow volumes conveyed by the Hortobágy Canal beginning with the moment of closure (Fig. 12) and by determining on basis of available cross sections (Fig. 13) the volume required for the storage of water as a function of time. Stages in the canal have thus been plotted against time (Fig. 14). These investigations were only possible using a successively approximating method on basis of Fig. 14. Trials made are exemplified in Table VIII. The correct opening stage was found when assumed values and those obtained in the last column showed a fair agreement. By extending the investigation to embrace a period of fifty years highest opening stages compiled in Table IX were obtained for each year. Probabilities of gate opening stages have been computed on basis of the 50 year series thus established by both the curve III of Pearson and by the empirical method (Table X). The gate opening stage having a probability of 0,5 per cent has been obtained as 87,00 m above Adriatic level. Data of the design flood level have been determined according to the well-known multiplication theorem of probability functions so as to yield 0,5 per cent as tl e product of probabilities of discharge and gate opening stage. Correspondingly, in the two extreme cases, a 99,99 per ent probability flood discharge pertains to an opening stage of 0,5 per cent probability and, in turn, a 99,99 per cent probability opening stage pertains to a flood discharge of 0,5 per cent probability. Practically 100 per cent should pertain, however, this case is not defined mathematically. The stage pertaining to a discharge of 0,5 per cent probability will be significant for the upper reaches of the Hortobágy Canal, where no backwater from the recipient is felt any more. On the other hand, a gate opening stage of 0,5 per cent probability accompanied by a 100 per cent, probability flood discharge will yield highest values in the vicinity of the mouth. Over the intermediate reach, as indicated by investigations, the highest flood level is obtained at a 0,8 per cent probability opening stage and a discharge of 62 per cent probability. Stages for the backwater each have been determined according to the method of Pawlowsky. A few examples of resistance moduli arc shown in Fig. lő while the computation itself is given in liable XII. Stages for a steadily travelling flood wave have been determined by the aid of gage relation curves. Besides the flood level of 0,5 per cent probability to be expected under present conditions the aim was the determination of the design flood level to be expected in the future. Resolving the plan for the development of bays along the Hortobágy Canal into five phases, it could be determined that the highest flood discharge is to be expected at the end of the fifth phase, by which time the full development of all bays will be completed. Detailed investigation methods used for present conditions could be applied successfully to those ensuing after full development as well. Results of these computations have been entered together with those previously described into the profile of the Hortobágy Canal shown in Fig. 16, respectively have been compiled in Table XIII. The method described can be applied to all rivers, or drainage canals, respectively — using proper judgement — to canalized river sections flood waters of which are received through pumping stations rather than naturally, or the mouth of which is closed by a gate to prevent high waters in the recipient from entering into the river or canal under consideration. (Author's summary translated by Z. Szilixissy, civ. eng.)