Vízügyi Közlemények, 1967 (49. évfolyam)

4. füzet - Rövidebb közlemények és beszámolók

(4 3) INUNDATIONS BY EXCESS SURFACE WATER IN WINTER-SPRING 1965-1966, IN HUNGARY By J. Szőcs, Civ. Engr. (For the Hungarian text see pp. 5) In spring, 1966 large areas were inundated in Hungary by excess surface water in plain-land regions, which form about two-thirds of the country. Extreme volumes of excess surface water were forecast already in autumn, 1965, from inundations in spring-summer, 1965, when excess surface waters covered about 100,000 hectares, and from the gradually rising groundwater table. As a result of wet weather conditions in autumn, the upper soil layer became practically saturated by December, and depending on the structure and physical properties of the soil, saturation attained a depth from 50 to 120 centimetres, so that in several sub-catchments it reached down to the groundwater table. Owing to saturation of the upper soil layer, about 75,000 hectares were inundated in December, 1965. Excess surface waters in the winter-spring period occurred substantially in two waves, the first of which appeared in December-January, while the second in February-March. Excess surface waters in December caused no major inundations, but resulted in a further rise of the then already high groundwater table. Control measures in this period were limited to the operation of permanent and portable pumping stations, removal of observed obstacles to runoff, emptying of storage ponds, and in January, to the removal of snow and ice from canals and structures. Control activities were intensified early in February. The situation was aggravated by the fact that together with excess surface waters several flood waves passed down the Tisza River and its tributaries, and consequently excess surface water could be discharged into the recipient by pumping only, and in some instances even pumping had to be restricted because of high water in the river. In several places water volumes surpassing the capacity of the canal network and pumping stations occurred, involving the danger of rendering main structures inoperative for extended periods. To counter this contingency waters were retained in numerous places and during control operations routing of waters, as well as portable pumps assumed great significance. The maximum pumping capacity during control operations was 392 cu.m/sec in permanent, and 133 cu.m/sec in portable pumping stations. Greatest inundation attained 359,000 hectares on the 16th February, which decreased to 236,000 hectares within a week. Control measures taken by individual district water authorities are described subsequently. HYDROLOGICAL CONDITIONS RESULTING IN INUNDATIONS BY EXCESS SURFACE WATER IN SPRING, 1963 By G. Kienitz, Civ. Engr. (For the Hungarian text see pp. 31) Plain areas of considerable magnitude were inundated by excess surface water in Spring, 1963 in Hungary. The occurrence of excess surface waters in Spring has been related by the author to four factors, of which two may be regarded as indirect, while two as direct ones. The first two comprise autumn precipitation, which determines the degree of saturation of the soil, and the severeness of soil freezeing, by which moisture is conserved, whereas the second two comprise thickness and rate of melting of the snow cover, as well as the volume of precipitation which accompanies snowmelt. Extreme values for at least three of these factors during the coming season could be anticipated in Autumn, 1965 already, and thus the extreme volumes of excess surface water that occurred in Spring, 1966 were by no means surprising. Forecasts proved to be correct by subsequent events. Autumn precipitation prior