Vízügyi Közlemények, Kivonatok, 1965

Dégen Imre: Az 1965. évi dunai árvíz és árvízvédelmünk fejlődése

(23) the time of peak discharge, to the end of June, the runoff volume through the Budapest gaging section was 50 cu.kilometres, while in the total flood period, the six months between the 1st March and 31st August, the total runoff conveyed by the Danube was 74.3 cu.kilometres. This volume is 1.7 times as high as that calculated for the same period with the average of the last 20 years, and exceeds by more than 4 cu.kilometres the annual average runoff during the last 50 years. One of the characteristic features of the 1965 highwater was that snowmelt runoff from the catchment contributed only 11 cu.kilometres to the total, corresponding to one-fifth of the runoff volume that passed up to the end of June. The general conclusion that warm rainfalls of high intensity play the main role in snowmelt floods, is supported also by an analysis of the ] 965 highwater resulting from both snowmelt and precipitation. In Chapter 112 the progression of the flood and forecasting of the progression is described. As indicated by the hydrographie map for the 14th June (Fig.

7over the greatest part of the Hungarian reach of the Danube and most of its tributaries flood waves involving stages which approximated, or surpassed 100% developed. The already grave situation turned then critical. The close sequence of flood waves developed as a consequence of snowmelt and repeated rainfalls over the upper part of the Danube catchment, and which overtook each other over the Hungarian reach created a situation which in itself was grave enough, but was affected adversely by the almost simultaneous highwaters of the Czechoslovakian, Hungarian and Yougoslavian tributaries of the Danube. Over the lower Hungarian reach and the Yougoslav reach downstream of the mouth of the Dráva River, the flood situation was aggravated by the extreme highwater on the Dráva Pàver and by the circumstance that the carrying capacity of the downstream bed was reduced by the simultaneous highwaters on the Dráva. Száva and Tisza Rivers. Over the reach above the mouth of the Dráva River the regime of the Danube is influenced mostly by its right-hand tributaries, of which the Inn River having the largest watershed, situated at the same time at the highest elevation (Fig. 8) is most important. The extreme flood would, however, have been turned into an unavoidable catastrophe by a combination of flood wawes from the Bavarian Danube and the Inn river. In the present case, fortunately, the flood wave of the Bavarian Danube overtook the one originated on the Inn River around Dunaremete only, and there the latter was slightly attenuated already. At the same time rising stages on the left-hand tributaries of the Danube had a highly adverse effect on stages over the central portion of the Hungarian Danube. It was especially the flood wave of the Vág River, which caused an unexpectedly grave situation at Komárom, where Danube stages exceeded the 1954 maxima already before the effect of the Vág flood became felt. Crevasses on the Czechoslovakian side occurred in this period, and the water volume of 1000—1200 million cu.m drawn away through these