Vízügyi Közlemények, 1976 (58. évfolyam)

1. füzet - Szlávik Lajos: Az 1974. évi körös-völgyi árvíz hidrológiai jellemzése

Az 1974. évi Körös-völgyi árvíz 39 Объем стока на реке (Фекете) Черный-Кереш составил 206 милл. м

3 (44,4 мм) а на р. (Фехер) Белый-Кереш — 193,0 милл м

3 (45,4 мм). Коэффициент стока проиблизительно можно принять за 0,5—0,6. Сравнивая паводок 1974-го года с прежними высокими наводнениями заметно, что хотя пики уровней и расходов на этот раз превзошли все ранее наблюдавшиеся — обьем половодья все же не достиг своего максимума. * * * Hydrology of the I !»7 '« flood in the Körös valley By L. Szlávik, Civ. Engr. The Körös Rivers, namely the Sebes-, the Fekete- and the Fehér-Körös originate in three branches on the territory of Boumania and crossing the Hungarian Plains discharge into the Tisza River. The examination of the 1974 Hood in this river system has contributed numerous new data to the knowledge of the hydrologie characteristics in this involved river system ( Fig. 1.). Heavy rains in May and June, 1974, have created the conditions for the development of a flood wave of extraordinary violence, setting record peak stages. The rainfall of 50 to 130 mm over the catchment from June 9 to 14 (Fig. 4.), the adverse geographical distribution thereof and the already full channel were the predominant factors resulting in the flood wave. On 15 June the stage on the Fehér-Körös has surpassed by 68 cm, while on the Fekete-Körös by 55 cm the highest levels on record (Fig. 2.). Since the stages continued to rise, the levees at the "delta" confluence of the two streams were cut to provide emergency retention storage (Figs. 5. and 6.J. In this way major damages to the economy could be avoided (Figs. 7. and 8.). In the 7100 hectares large emergency reservoir 118 million m

3 water were stored and storage space was filled in 82 hours. The observations and measurements made in connection with emergency storage have provided a number of important hydrological information. In the gaging cross sections upstream of the levee cuts "inversed" flood loops were observed (Fig. 9.). In the 11 cross sections along the Körös rivers 221 discharge measurements were made (Table I.) and the data obtained throw interesting light on the properties of the flood loops. In the levee cuts 107 discharge measurements were performed in an effort to trace the filling and emptying of the emergency reservoirs, further for estimating the rate of dewatering (Fig. 12.). The water regime in the "delta" was reflected reliably by the measurement data (Fig. 10.). From the dynamics of filling the emergency reservoir it was concluded that in this flood wave the diversion of relatively small water volumen has resulted in an appreciable reduction of peak stages (Fig. 11.). In this respect local drawdown has played an important role, as illustrated clearly by a comparison with the flood liydrographs estimated without emergency storage (Fig. 13.). According to these estimates without emergency storage the peak stage on the Fehér-Körös would have been higher by 34 cm, while on the Fekete-Körös by 38 cm (Table II.). From the inundated area 80% of the water was removed by gravity (through 3 further cuts in the levees) and 20% by pumping, accomplished practically in 23 days (Figs. 16. and 17.). For attaining the highest possible rate of unwatering by gravity ( Fig. 15.) the flow in the indundated area was controlled by cutting artificial terrain features ( Fig. 14.). The total runoff volume on the Fekete-Körös was estimated at 200 million m

3 (44,4 mm), while on the Fehér-Körös at 193 million m

3 (45,4 mm). The avarage runoff coefficient was estimated at 0,5 — 0,6. By comparing the 1974 flood with earlier major floods ( Fig. 18. and Table III.) it will be perceived that the flood wave involving extremely high peak stages, discharges and of unprecedented violence has conveyed much less water than the greatest floods on record thus far.