Floodplain aggradation caused by the high magnitude flood of 2006 in the lower Tisza region, Hungary

The area of floodplains in the Carpathian Basin was dramatically reduced as a result of river regulation works in the 19th century. Therefore, the accumulation processes were limited to the narrower floodplains. The aims of the presented study are to determine the rate of accumulation caused by a single flood event on the active, narrow floodplain of the Lower Tisza and to evaluate the relations between the aggradation, flow velocity during the peak of the flood and the canopy. The uncultivated lands in the study area cause increased roughness which decreased the velocity of the flood, influencing the rate of aggradation. The highest flow velocity was measured on points where the flood entered to the floodplain and at the foot of the levee. These points were characterised by thick (over 50 mm) and coarse sandy sediment. In the inner parts of the floodplain flood conductivity zones were formed, where the vegetational roughness was small. In the inner parts of the floodplain the rate of aggradation was influenced by the geomorphology and the vegetation density of the area.