Morphological investigations in the River Odra

Since 1992, the Federal Institute of Hydrology (Bundesanstalt für Gewässerk- unde - BfG) performs morphological investigations in the river Odra downstream from the confluence of the river Neisse (Nysa Luzycka). The results of these investigations give a clear insight into the morphodyn- amic behaviour of this part of the river and indicate that on average 380000 t of suspended solids and 130000 t of bed load are transported by the river Odra at Hohensaaten per year, with a distinct seasonal variability in the case of suspended solids. Detailed studies on type and composition of the bed substrates have revealed that the river bottom is composed of very fine material: at Ratzdorf already 75 % of the bed material is finer than 2 mm, at Widuchowa almost all of the river bed material consists of sand finer than 0.63 mm. Because of the high sensitivity of the river bottom to discharge increases and the corresponding increases of bottom shear stress sand was found to be the dominating fraction of the suspended load in case of extreme flood events.