Vízügyi Közlemények, 1963 (45. évfolyam)

4. füzet - VIII. Könyvismertetés

"(55) THE 1963 SPRING FLOODS IN HUNGARY (For the Hungarian text see pp 279—341 ) 1. Introduction. The 1963 spring floods (By M. Breinich Civ. Eng.) The extremely severe winter 1982 — 63 created in the northern and western parts of Hungary conditions in which inundations from both river- and excess surface waters were imminent. The situation was much more favourable in the south-eastern and eastern parts of the country. By the end of the winter the thickness of the snow cover was only 3 — 5 cm over the southeastern parts, 25 to 30 cm over the northwestern parts, while 117 and 50 cm in the northern and western mountains, respectively. At the same time the soil was frozen and of a high water content. A further aggravating factor was the ice cover over the entire Hungarian reach of the Danube River, starting from the Yougoslav border downstream from which an ice jam developed at about 30 km distance. Preparations had to be made therefore against both an ice-carrying flood on the Danube River, and inundations by smaller water-courses and drainage canals in the northern and western parts of the country. Thanks to the favourable weather conditions the ice cover broke up between the 12th and 18th March without having caused any serious floods. Yet owing to the sudden melting of the snow on the frozen soil between the 10th and 15th March, flood waves exceeding highest peaks on record by 20—40 cm travelled down the tributaries of the Danube and Tisza Rivers, as the Rába, Marcal and Sió Rivers, the Nádor Canal, the Zagyva, Tarna and Sajó Rivers, as well as on the border stream between Hungary and Czechoslovakia, the Ipoly River, The flood levees we re overtopped at several places, and the levees ruptured at several points along the Marcal, Tarna, Zagyva and Ipoly Rivers, resulting in inundations of considerable extent. The areas endangered by floods and mentioned in the review are illustrated in Fig. 1. 2. Meteorological factors (By 7. Vancsó, meteorologist) Weather conditions during the winter 1962 — 63 are discussed according to periods. The first period commenced on the 22nd November, 1962 with country-wide extensive snowfall. The resulting snow cover was 30 — 90 cm thick west from the Danube, but was insignificant east of this line. A period with mild night frost ensued and lasted until the 10th December. Rainfall in the second, milder period from the 31st December to the 8th January completely saturated the soil. In the ensuing 25 day period from the 9th January to the 2nd February temperatures dropped to minus 15 to 22 Centigrades. The soil froze completely to great depths and by the end of this period every watercourse was covered by solid ice. On the 3rd, as well as on the 5th and 6th February considerable precipitation in the form of snow and rain fell in the Carpathian basin (Fig. 2.1 ) caused by two cyclones travelling at high speed from SSW to NNE (Fig. 2.2). This set of meteorological conditions created flood waves on the Tisza River and its tributaries, but gave no concern as far the ice-carrying flood on the Danube River was considered. Mild temperatures combined with rainfall from the 10th to 22nd February created again high stages on the Tisza River system, with gage readings between 88 and 96%. This period was concluded by a cold wave. Daytime temperatures rose to above the freezing point from the 3rd March, and to the 7th night frost only occurred. This meteorological pattern is of a tvpe unlikely to cause ice-carrying flood on the Danube River (Fig. 2.3 top). The rainy period from the 9th to the 13th March which caused extraordinary floods on smaller watercourses and creeks was again of a meteorological pattern likely to induce floods on the Tisza River and its tributaries (Fig. 2.3 bottom). Between the 12th and 16th March stages exceeding the highest ones on record ensued on the small watercourses in the western and northern parts of the country as well as on Lake Velence situated west from the Danube. This type of meteorological pattern proved to cause no dangerous conditions on the Danube River, from which the ice cleared without trouble. It is finally established that the classification of meteorological patterns according to type in the previous years was very helpful to the flood forecasting service.