Weir 1, Weir and footbridge in Leopoldstadt, Austria

Weir 1 is a footbridge combined with a water control structure spanning the Danube in Vienna. The prestressed concrete construction manages water flow while allowing pedestrians to cross the river above it.

Weir 1 was built between 1976 and 1978 as one of three weirs regulating the water level of the New Danube. It was founded on diaphragm walls in Tertiary sands and clays; exploratory drilling revealed a fault zone, forcing the weir axis to be shifted. In June 2017 an underground hydropower plant with an Archimedean screw began operating at the site.

Since June 2017 an underground hydropower plant has operated at Weir 1, a joint project of Wien Energie and the city's waters authority (MA 45). Its Archimedean screw, 15 m long and 3.20 m in diameter, turns at 25 revolutions per minute and uses a head of about 3.5 m to produce an average of 45 kW, enough for roughly 130 households.

The structure is easily accessible and offers clear views of the Danube and its water management systems. You can walk across and observe from both sides how the weir and bridge work together.

The structure demonstrates how engineers combined flood control and pedestrian traffic in a single construction. The prestressed concrete technique made it possible to create a slender design that requires less space than traditional methods.