Vízügyi Közlemények, 1997 (79. évfolyam)
4. füzet - Szlávik L.-Bálint G.: az 1997 tavaszi-nyári ár- és belvizek és a védekezési munkák
468 Szl ávik L. — . Bálint G. Flood and excess water defence alertness duties, which had been ordered by the authorities between January and August 1997, are summarized in Table V. Flood defence alertness duty was declared in January-February (wich ice-defence), in April, May, June, July and August (Figure 11). The total length of flood-defence lines on simultaneous duty was the largest (655 km) on the 22-23 of July. Upon the heavy rainstorm of the night and forenoon of 14—15 June an intensive flood wave was launched ont he River Berettyó, near to the common Hungarian/Rumanian border (Figure 12.). The hydrograph was flattening out as it travelled downstream and the alertness duty could be terminated on the 21st of June. Technical flood defence activities were also needed at the River Lajta at the time of the Danube flooding: strengthening and rising the dikes and the opening of an emergency storage reservoir on the left bank of the River (Figure 14). These measures were able to save Mosonmagyaróvár from flood inundation. In the area affected by the Gabcikovó hydropower scheme the flood flow of Danube was released by both the "old" rover channel and the power canal (Figure 13). Due to long lasting high water levels seepage and leakage have been observed at many planes along the defence lines and measures had to be taken at several locations to counteract the development of boils and other harmful leakage formations. The two most endangered places were in the vicinities of Surány and Dombori. Experts of the water authority were able, with the help of the local population, to successfully defend these dikes by building counter-pressure basins using sand-bags. The organization of the defence activities was highly supported by a special condition, namely that recently and just at the time of the flood two new legislations, directly stemming from the new Water Law, have been released and put into practice, providing the legal frame for the smooth operation. Excess water situation in Hungary. In the fall of 1996 high rainfall had nearly saturated the upper layer of the soil and during the winter this layer became frozen, melting again in the spring. As a result of this relatively small precipitation caused the oversaturation of soil and the occurrence of surface excess water inundations. The excess water drainage pumps had to be put into operation and excess-water defence alertness duty had to be declared at several locations. In the Tisza river basin excess water drainage activities were carried out in an almost continuous basis (Table VI.). The high rainstorms of the summer of 1997, with the simultaneously occurring floods which limited water release capacities, necessitated extensive excess water drainage operations in the North-Transdanubian part of the country and in the Tisza and Körös river valleys. Extremely high precipitation in association with other unfavourable conditions, of the Upper-Szabolcs sub-basin created dangerous excess water situation (Figure 19.). The highest inundation covered nearly 400 sqkm (not including oversaturated areas) and the pumping stations lifted 208 million m 3 water from the main drainage canals to the recipient rivers. The total cost of excess water defence activities was 212 million HUF. In addition to the Hungarian flood and excess water defence activities the Hungarian Water Management Organization provided technical aid to Poland where the highest flood of the century caused devastating damages. On the 18th of July the Hungarian Central Organization of Flood- and Excess Water Defence (ABKSZ) and the Water Authority of the Central Tisza River Valley (KÖTIVÍZIG) sent a mission of 26 experts and 20 high capacity pumps to Poland for helping the defence work there. Hoch- und Polderwässer im Frühjahr und Sommer 1997 und ihre Bekämpfung von Dr.-lng. Lajos SZLÀVIK, PhD und Dipl.-Ing. Gábor BÁLINT Im Sommer 1997 entstanden in recht ausgedehnten Gebieten Mittel- und Osteuropas Wetterlagen, die als extrem bezeichnet werden können, infolge deren vieleorts 50- bis 1 OOjährliche Hochwasserwellen verzeichnet wurden. An einigen Flüssen des Raumes kam es zu katastrophalen Hoch-
