Weir 2, Prestressed concrete footbridge in Vienna, Austria

Weir 2 is a weir in the Neue Donau in the south of Vienna, completed in 1988, which also carries a footpath and cycle link to the Donauinsel. It has five weir bays with a clear width of 30.6 metres each. The closures are hydraulically operated pressure segments with fixed overflow hoods; two of them have an additional retaining flap, and the segments are designed to withstand tensile stress because water can flow through in the opposite direction.

Weir 2 was completed in 1988 as one of three weirs regulating the water level of the Neue Donau. Trial borings showed the Tegel clay lay only at a depth of 40 metres beneath highly permeable sands, so the site was moved 470 metres from the planned spot; a required remediation of contaminated land in the Lobau forced a further shift of 50 metres.

Weir 2 is a fixed structure: unlike the movable weirs at power plants, its five gates normally stay in place. The closures are hydraulically operated pressure segments with a fixed overflow hood, and two of them carry an extra retaining flap. Because water can flow through in the opposite direction, the segments are also designed for tensile stress.

Weir 2 is reached on foot or by bike from the Donauinsel and serves as a crossing of the Neue Donau. The structure is a fixed weir that is normally not moved, so the five 30.6-metre-wide weir fields with their hydraulic pressure segments can be viewed from the crossing at any time. The site lies in the south of Vienna, near the Lobau.

The weir's site was moved twice before construction: test borings found Tegel only at 40 metres depth under highly permeable sands, forcing a 470-metre shift, and a required remediation of contaminated land in the Lobau caused a further 50-metre move.