The results of theoretical investigations predict a riverbed degredation in the Salzach in the area of the railway bridge. So the existing rockfill was to be replaced by a massive vertical drop structure in the riverbed, which is located 50 m downstream of the railway bridge. The structure leads to a reduction of the bed load transport and therefore protects the riverbed in the surroundings of the bridge piers from further scouring. The institute carried out physical model experiments for a straight (rectilinear) and a curved vertical drop structure.
In the physical model the curved structure proved to be the better option and was implemented in the river. The advantage of the curved structure is that the scour forms in the middle of the river, which results in lower costs for bank protection and improves the stability of the entire structure at the same time.
Scour of the linear weir from the right hand side
Physical model with scour formation in the tailwater of the curved vertical drop structure
One hundred year flood
View from the right bank of the Salzach on the curved vertical drop structure in the physical model
View similar to the photo above in nature in summer 2004
centennial flood (2.100 m³/s) through the vertical drop structure in the physical model
Flood (2,300 m³/s) on 12.08.2002. The structure worked well.