yes, this is a weir (with emergency lock)
little info from the net:
After a barrage had already been built in Bremen-Hemelingen as the end point of the Unterweserkorrektion, another barrage was built in Dörverden from 1907 to 1914 in order to enable the delivery of Weser water for the irrigation of agricultural areas between Hoya and Bremen in dry times. [1] The first weir, a steel lattice construction, was built in 1911/1912 by the Aug. Klönne company. [2]
The barrage Dörverden at Weser kilometer 308.8 was built with the current weir from 1931 to 1933 as the second barrage of the Middle Weser in order to keep the water level as constant as possible and to make the waterway passable for large ships. The weir is 104.90 m wide and consists of two 40 m wide fields, the third field is 24.90 m wide. The water level is 4.60 m. In summer the headwater level is kept constant at 14.60 m above sea level, in winter at 15.10 m above sea level. The weir is operated by the Verden Waterways and Shipping Office. [3]
Cyclists and pedestrians can cross the weir over the Weser between Dörverden and Hilgermissen from March 15 to October 15, but using stairs with side sliders. [4]