Historical and Seasonal Trends in Flood Conveyance, Tisza River, Hungary

R. A. Venczel and N. Pinter
Southern Illinois University Carbondale

This study compiled hydraulic and hydrologic data for stations situated on the Tisza River, Hungary: Tivadar, Vásárosnamény, Záhony, Kiskóre, Szolnok and Szeged. Data were obtained from the Hungarian hydrological authority (VITUKI). This research had two objectives: (1) to identify causal mechanisms driving recent increases in flood stages, and (2) test for a seasonal change in the stage-discharge relationship. The first objective involved testing the hypothesis that increased flooding on the Tisza River is the result of conveyance loss due to (1) channel and floodplain aggradation and/or (2) increased channel or floodplain roughness. Conveyance loss can be caused by three and only three geometrical changes: decrease in width, depth and/or flow velocity. Aggradation affects the width and depth, while roughness affects the flow velocity. The second objective of this project involved testing the hypothesis that there is an identifiable seasonal signal on the Tisza River.

Results showed a decrease in conveyance of above-bankfull discharges at five of the six stations due to decreased flow velocity. This has increased flood stages on the Tisza River by up to 2.3 m. An increase in conveyance of belowbankfull discharges was observed at five of the six stations, and correlated to increased velocity and cross-sectional area. Seasonal analysis results showed two trends at different stations. The first trend had stages reaching maxima during winter, and the second trend had stages reaching maxima during spring. These Differences in stage between seasons reached levels of ~2 m.

AAPG Search and Discover Article #90087 © 2008 AAPG/SEG Student Expo, Houston, Texas