Vízügyi Közlemények, Kivonatok, 1965

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

(44) In Chapter 1 a detailed description is given of the Central-Transdanuvian flood levees (Fig. 1), and especialy of those extending along the reach downstream of Dunaföldvár. Hydrological parameters relevant for the condition of levees have been compiled in Chapter 2. From Fig. 3 it is concluded that whereas stages over the Austrian Danube reach and even at Bratislava remained below previous maxima, the highest ice-free stage was exceeded at Komárom for 4, at Budapest for 9, at Baja for 18 and at Mohács for 24 days. A comparison of durations of three extreme ice-free floods is given in Fig. 4. The probability of occurrence of peak stages experienced over the reach has been estimated at 0.7 %, corresponding to a frequency of recurrence of 160 years. However, as far as the probability of duration of dangerously high stages is concerned — like the ones which were experienced for long" periods during the flood — recurrence frequencies around several hundred years have been calculated. i'lood hazards over the reach are illustrated in Fig. 5 by the profile

T indicating that over the upper portions ice-run floods represent the main source of danger. The difference between design ice-run flood stages and ice-free, flood stages is greatest here. Flood control operations in 1965 were therefore centered on the section downstream of the mouth of the Sió Creek. An account of the behaviour of flood levees during high water is given in Chapter 3. From among the effects to which the levee body was exposed during the flood, saturation was most detrimental and was accompanied by similarly unwanted phenomena. A photograph showing saturation of the levee is reproduced in Fig. 6. An other instance, where saturation was due to a highly impervious berm, is shown in Fig. 7. The influence of the flood on the surroundings of the levee and on the subsoil is dealt with subsequently. Methods applied for active flood control are described in Chapter 4. The organization of flood control in the Central Danuvian District is outlined. together with activities of the special hydrometry group established for the flood period, labour problems, material supply, transportation, mechanical equipment, lightung, communication and methods ol levee protection, which are illustrated in Figs. 9 to 12. Main experiences gathered during the flood have been summarized in Chapter 5. On the basis of this evidence a program is given for improving preventive and active protection. Suggestions were elaborated for strengthening the levees, and construction work was started immediately accordingly after the flood wave had passed. A levee cross section permitting two-way traffic on the crest and mechanical maintenance of the grass cover of the slopes are provided. In addition the shape of the cross section allows for seepage through the levee body. The resulting cross