Hidrológiai Közlöny 2005 (85. évfolyam)
3. szám - Fiala Károly–Kiss Tímea: A középvízi meder változásai az 1890-es évektől az Alsó-Tiszán
F1ALA K. - K.ISS T : A kOzépvizi meder változásai 65 Cross-sectional changes of the river-bed on the lower section of Tisza River sincc 1890 Fiala, K. - Kiss, T. Abstract: Several floods were detected in the river system of I isza between 1998 and 2001. when on some sections Ihc highest stage in history was recorded. The increase in flood stages could be explained by different reasons, as the changes on the catchment, the floodplain or the river-bed. The aims of the investigation were (1) to determine the temporal and spatial changes in the cross-sectional parameters of the river-bed; and (2) lo estimate the effect of cross-seclional changes on banklull discharges As the greatest quantity of water is drained in ihc clianncl during Moods instead of on the floodplain (Tőrük, 2000), the area of cross-sections fundamentally influences the water-level al the same slope and discharge conditions The studied reach is situated on the lower section of Tisza (205-225 Dem). The cross-sections were made by the Hydrological Servicc in 1890, 1929, 1957, 1976, 1999 and 2001 At the cross-overs the maximum width and mean width decreased by 8-10 % and 15-19 % respectively (max. decrease 35 %). Since 1890 the maximum depth increased by 3-4.6 m (by 45 %). These changes resulted a cross-sectional area decrease, but only by 3 5-5% Along the studied reach few number of freely developing meanders can be found. In the axes of these meanders the cross-sectional area decreased by 1-2 % during the last 100 years However, most of the meanders have bank protection on the concave banks Therefore, these banks do not show lateral erosion sincc the training, though their convex counterparts host intensive accumulation. Thus ihe shape of the cross-sections changed; the width decreased by 22-45 % and the maximum depth increased by 230 %, resulting considerably great cross-sectional area decline. The area of cross-section influences the discharge belonging to a given stage, or the water-level belonging to a certain discharge Therefore, we have calculated how the changed areas influence the water-conductivity of the river-bed; calculations were made for average slope (0 00029) and velocity (0.7 m/s) conditions. The greatest channel conductivity decrease was calculated in case of meanders with revetments, where the discharges belonging to bankfull stage were decreased by 6.2-13.5 %. The decrease was uneven between the different dates, but it is important if one considers that on the 20 km long study reach 9 I km revetments (45 of the total 9length) were completed, thus along this section the stability of the river has changed, the water-conductivity conditions of the river-bed became less favorable. Key words: bed regulation, river regulation, River Tisza A Duna Múzeum Európai Közép Galériája 2005. május 4 - június 5. között Esztergomban Somogyi Győző festőművész alkotásaiból TÉRKÉPEK címmel kiállítást rendezett, amelyet dr. Prokopp Mária művészettörténész nyitott meg. (Fenti ábránk a kiállítás címadó ábrája volt)
