Changes of cross-sectional morphology and channel capacity during an extreme flood event, lower Tisza and Maros rivers, Hungary

Abstract

When examining the characteristics of individual floods Hungarian researchers primarily investigate hydrological and hydraulic processes, whilst the relation between flood events and morphological changes of the river-bed are widely ignored. The present research quantifies the morphological changes of two cross-sections of the lowland reaches of the River Tisza and its tributary, the River Maros, during a high magni-tude flood which occurred in spring 2000. During the flood several key morphological cross-section variables (mean depth, channel bed eleva-tion, maximum depth, cross-sectional area and channel capacity) were monitored. Relationships between these data and daily river stage height series of the flood and specific stream power were determined. Results suggest that the identified morphological changes highly affect the channel capacity of the two cross-sections during the flood event. The channel capacity changes (9-10%) were almost identical for both study sites. However, different morphological processes characterised the two cross-sections. We found that morphological parameters de-pend not only on the actual stream power, but the available amount of sediment for transport, the rate of stage and stream power change.