Summary:

The hydrotechnic structures of the flood protection system of the Wrocław city were realized after the flood in 1903. They protected the city against the discharges equal 2400m3/s. During the catastrophic flood in 1997 the maximal discharge in Odra river was much higher, about 3640m3/s. The stages and discharges in the whole Wrocław Hydrotechnic System (WHS) were also higher then in 1903. It concerned also the knot Odra-Widawa. The high stages and discharges leaded to the destruction of the inlet weir to the channel Odra-Widawa and of the channel’s embankments, what caused the inundation of the city quarters Kowale and Wojnów. The presented paper is an attempt of the determination of causes of the weir Odra-Widawa destruction. The hydrogrammes of stages during the flood were determinated on the base of measurement performed by the Water Administration in Wrocław on the upstream gauge of the sluice Bartoszewice. It could be stated that the destruction of the weir and embankments was related mainly to the blockage of a part of weir by branches brought by the stream and to the small hydraulic capacity of the Strachociński bridge on the channel Odra-Widawa.