Vízügyi Közlemények, 1963 (45. évfolyam)

4. füzet - VIII. Könyvismertetés

"(56) S. Ice conditions on the Danube Hiver ( By Dr. Z. Károlyi, Civ. Eng.) The ice cover on the Danube River developed in the third, most severe frost period which lasted from the 9th January to the 2nd February. Daily mean temperatures, temperature deficiencies as well as the formation of running and solid ice is illustrated in Fig. 3.1. Solid ice developed already during the second frost period, 20th to 30th December, 1962, downstream from the Hungarian-Yougoslav border, at Apatin, (river station 1401 km) and at Bogoyevo (river station 1367) which extended up to the border and which developed during the subsequent days into an ice jam at Apatin on Yougoslav territory. All the ice from the 77 km long ice cover was carried under the jam between river stations 1401 and 1409 km and raised the waterlevel by 3,8 after the 9th January (Fig. 3.2). The two cross sections determined by Yougoslav authorities are shown in Fig. 3.3, the vicinity of the jam is illustrated in Fig. 3.4. As to be seen from these the water underpassed the jam at the lefthand side of the central bank, scoured the bottom to great depths and flowed around the jam in the left branch at high velocity and with open surface. Yougoslav authorities succeeded after long difficulties in blasting a 50 m wide channel in the jam. Heavy ice runs started again in the third, very severe frost period beginning with the 9th January. This ice however, was halted a{ the solid ice of the Apatin jam. Consequently the second ice cover developed at a much higher rate on the Danube. The days by which the solid ice developed earlier after the beginning of frost than in other years is shown in Table I. The solid ice cover developed on the flat Danube reach at the average rate of 43 km/day. The huge ice volume, the dangerous jam at Apatin and the bulging ice masses on the Upper Danube justified the preparations made for the case of an ice-carrying flood. Integrating curves of daily mean temperatures during long and extended winters are shown in Fig. 3.6. Among these the winter 1962 — 63 occupies an intermediate position. Meteorological conditions highly favourable for the departure of the ice cover ensued. Temperatures rose at a slow rate, no wave arrived from the upper reaches and, most important, the spring temperature rise was higher in Yougoslavia than in Hungary (Fig. 3.7). Under the combined effect of these factors the ice from the Hungarian Danube found no obstacle to its passage and departed fairly easily with but local jams causing minor backwater only. These slight rises in the waterlevel is shown by the profile of simultaneous stages in Fig. 3.8. From the smooth departure of the ice cover under the prevailing favourable meteorological conditions the conclusion to be arrived at is that the river training works carried out so far resulted in considerable improvement, while the reach above the mouth of the Dráva River is in need of far reaching channel regulation. A great number of ice bottlenecks are still to be found over this reach. The new Hungarian ice breaker fleet of seven vessels was offered the first opportunity to prove its worth. They successfully prevented the development of jams and accelerated its breaking up. 4. Hydrological conditions of floods due to river- and excess surface tvater in Central Trans-Danii

via (By M. Bratán, Miss K. Csongrádi and I. Zsuffa, Civ. Engs.) One of the areas which suffered from inundation was the central part of the country west from the Danube River, which area comprises two major lakes, Lake Balaton and Lake Velence and a river system formed by several smaller watercourses. In the snow cover overlying the soil which froze to great depth in winter 1963, the water content stored was 60 — 70 mm even in plain regions (Fig. 4.1). Thawing which began in March caused this volume of water to run off during a few days and created extreme floods on the smaller watercourses in Central Trans-Danuvia. In order to ensure the passage of the flood waves without damage the water authorities created temporary flood reservoirs and prevented thereby the indundation of more valuable land further downstream. The District Water Authority in charge of the area organized well before the flood wave the observation and collection of characteristic flood data. The water content stored in the snow cover was measured, hydrographs during the floods were observed, flood discharges were measured and peak discharges were estimated in many sections after the passage of the flood wave from traces left behind (Fig. 4.2).