Vízügyi Közlemények, 1954 (36. évfolyam)

2. szám - XV. Szilágyi József: Az Erzsébet-híd roncsainak hatása a mederalakulásra

(29) SOME LESSONS FROM TISZA RIVER FLOOD STATISTICS By T.. Puskás (Figures on pp. 157 — 168 of Hungarian text) • N UDC 551.482.215.1 : 627,51 The design flood stage of the Tisza River agreed upon in hydraulic planning had been determined as the upper envelope of peak floods recorded, with certain corrections. To compare it with flood records a statistical analysis of the Tisza floods was maid by the method of the probability calculus. The investigation covered the period of 1888 — 1952 (65 years), considering the maximum flood flow due to spring snow runoff of each year at nine sections of the river (Fig. 1). This paper presents some interesting experience acquired in preparing the evaluation and the most important results of the calculation. The statistical analysis was based on discharges corresponding to the aforementioned river stages. On the very gently sloping Tisza River (t = 0,02—0,1 %

0) the discharge at the same stage is considerably variable corresponding to changes of slope of the stream. For the determination of discharges this problem had to be examined more in detail and rating curves had to be extrapolated. At the Záhony section, where a change in slope occurs only in consequence of rise and fall, the rating curve was referred to the steady-flow slope. Therefore results of discharge measurements executed at different slopes were reduced on the slope corresponding to crest stage, depending on the water stage only and taken for equal to the slope at stable river stages (Fig. 2.). At Szeged the slope of the stream is variable because of the variable backup effect of the Danube ; the slope of the stream could be at any time characterized by the coincident gauge height at Zenta, the neighbouring gauging station, and discharges could be determined with the aid of an auxiliary diagram drawn on this basis (Fig. 4.). The mean velocity diagram of the section at Polgár relative to the main channel and presented in Fig. 6. indicates that the method of extending rating curvfcs cannot be applied mechanically to stages overflowing the banks, for this may lead to substantial errors. To improve the accuracy of series of discharge data, determined one by one, independently of one another— for the examined sections, these had to be confronted and coordinated. Table I. lists mean annual discharges and differences between mean annual discharges at contiguous sections of the river. Dotted characteristic curves of Fig. /., permitting no interpolation, also show the harmony of data of different sections. As a summary of the statistical analysis to characterize Tisza spring floods Fig. 9. presents the longitudinal hydrologie section of computed flood discharges of different probability and of the minimum, maximum and mean flood flows recorded during the period investigated, as well as the change of the coefficient of variation along the river. Fig. 10. shows the schematic longitudinal section of calculated flood stages of the Hungarian Tisza, of 0,5, 1 and 3% probability, as well as of the design flood stage based on records. The probability of the latter is not the same all along the river, which is in conformity with experience. ОПРЕДЕЛЕНИЯ КОЭФФИЦИЕНТА ИНФИЛЬТРАЦИИ И РАСХОДА ПРОДОЛ-. ЖИТЕЛЬНО ВЫБИРАЕМОЙ. ВОДЫ В КАРСТОВЫХ УСЛОВИЯХ Автор : X. Кесслер (Рисунки см. на 179 — 188. стр. венгерского текста) ОДТ 551.491.78 С точки зрения водохозяйства весьма важной задачей является количественное определение расхода воды, выбираемой из карстовых пород без нарушения естественного водохозяйства. Решение этой задачи можно произвести только в том случае, если точно знаем коэффициент инфильтрации. На основании многочисленных измерений расхода воды истоков, произведенных в рамке водного кадастра Водохозяйственного Научно-исследовательского Института можно установить, что значение коэффициента инфильтрации изменяется в широких пределах (иногда между 7 и 70%) даже на одной и той же территории. Исследования показывают, что суммарный годовой расход карстовых истоков зависит не только от количества годовых осадков, а в значительной мере и от внутригодового распределения осадков (рис. 1.).