Vízügyi Közlemények, 1954 (36. évfolyam)

2. szám - XV. Szilágyi József: Az Erzsébet-híd roncsainak hatása a mederalakulásra

(68) ON THE CONTROL OF SURFACE WATER IN HUNGARY By J. Pichlcr (See pp. 451—466 of Hungarian text.) 627.5 (439.1) The Great Hungarian Plain was in the XVIII century still a marshland of great extension, fed by spring floods of rivers. To eliminate flood damage a great many cut-offs were made and levees were built. On the Danube cut-offs were necessary because ice jam was often produced in sharp bends and caused grave floods. On the exceedingly gently sloping Tisza River (J = 2 — 5 cm/km) and on its tributaries in the Great Plain speeding up the withdrawal of floods was the principal aim. Therefore 112 cut-offs reduced the alluvial section of the Tisza from 1213 km to 760 km, whereby the duration of spring floods at Szeged was reduced from 5—6 months to 8 — 10 weeks. For the protection of the flood area of about 2,2 million ha levees of 3800 km total length were built at the expenditure of moving more than 200 million cu.m. of earth. This work was supplemented by reclamation of 1,1 million ha. of marshland, the construction of a canal network of 25 000 km extension for artificial drainage of the former flood area, with 195 pumping plants (ratings : 29 000 h.p., 365 m

3/sec> and numerous other works. The gigantic water control work, the portion of which pertaining to drainage of harmful waters has been executed during the last 75 years, is responsible for the reclamation of 1/

i of the total area of the country i.e. of 1/3 of its cropland. Thinly populated areas have been settled, a dense railway and highway network has been built, malaria eliminated, and almost half of the population is living on reclaimed land. During the last 10 years repair of big damage clone to protection works during World War II., strengthening of levees, extension of the canal network, and boosting pump capacity have been the main tasks. Of course reclamation work cannot be regarded as completed. Development is urged by the following reasons : 1. The great economic development of reclaimed floodland and investments made there, call for increased security against flood damage ; 2. Flood stages of rivers confined between levees have risen, the increase of the density of canalization network speeds up runoff, and the peak discharge of canals increases. 3. During the last 15 years extraordinary floods and accumulations of water in low-lying areas have increased. Most important agenda are the following : 1. Flood protection: Reinforcement of levees by topping them up to at least 1 m above the hitherto recorded maximum flood stage; along levees on permeable subsoil piping has to be prevented by auxiliary dykes, wrongly traced levee sections have to be corrected. Degraded riverbed sections facilitating ice jams have to be regulated, the rise of the river bottom on the Upper Danube (1 cm/year) has to be eliminated or reduced. Partial afforestation of flood areas to protect levees from beating by waves. 2. Boost of the efficiency of flood protection service by increased help by aviation (reconnoitring, material transport), reinforcement of permanent motorized service (light pneumatic sheet pile drivers, transportable power and lighting plant), perfection of flood forecasting. 3. Reclamation drainage : Increase of drainage capacity by doubling the present rating of 20,4 1/sec. km

2, better storage of winter precipitations. Mechanization of canal upkeep, production of adequate excavators (3 million m

3 capacity a year). Standardization of construction of pumping plants, duplicate-production of pumps. Successive electrification of pumping plants, with supply from two sources. 4. Soil improvement drainage. For the control of the water cycle of the soil, regulation of the ground water table on 230 000 ha ; 100 000 of these marshland.