Tisza Pilot Description
River Tisza is one of the largest tributary of Danube with a total catchment area of 157000km2 and it is shared by five countries (Ukraine, Romania, Slovakia, Hungary and Serbia). The river itself is the frontier along several kilometres between Ukraine and Romania, Hungary and Ukraine and between Slovakia and Hungary. It has a total length of 966 km.
During high water periods agriculturally used land becomes flooded. Barrages have been constructed in the river at Tiszalök (rkm 523 ), Szolnok (rkm 332) and Szeged (rkm 180).
Most of the Tisza’s course can be characterized as a lowland river (exception: upper section). Its hydrological regime fluctuates extremely and is determined by the discharge from middle-mountain tributaries. Periods of high discharge and water levels lie in spring, when large floods occur regularly. Low water levels characterize the summer. The Tisza transports large amounts of sediments (10–11 M t/a; Gatescu, 1990).
Due to drainage measures, which were undertaken in the 18th and 19th centuries the river course was shortened by 40 % (Dobrosi et al., 1993; Varga, 1997). This led to an increased velocity and riverbed erosion. Another consequence of these measures is the reduction of the floodplain area from 7,542 km2 (HU: 4,637 km2) to 1,215 km2 (HU: 914 km2).
After a relatively long dry period unprecedented series of extreme floods hit the Upper- and Middle Tisza River between November 1998 and March 2001. During the 28 month period four extreme floods occurred, as a consequence of which the total duration of flood alerts reached 24 month. Within this, extraordinary alerts lasted 9 month. The November flood in 1998 as well as the March flood in 2001 brought new records in flood peaks along the Upper-Tisza, the latter caused even dike breach there. However, these floods due to the attenuation of the single flood waves resulted in a high, but not extreme flood on the Middle-Tisza section which is subject of the present investigation, being the selected pilot site downstream Szolnok.