Aue des unteren Sengbachtals, Nature reserve in Solingen, Germany.

Aue des unteren Sengbachtals is a 6.41-hectare nature reserve in southern Solingen, on the border with Leichlingen. It covers a 30 to 60 m wide, roughly 1,400 m long stretch of the Sengbach valley floor between the Sengbach dam wall and the stream's mouth on the Wupper near Glüder, bordered by steep slopes up to 60 m high. The stream's flow varies sharply because of the reservoir: the upper course can dry out in summer, while overflow brings flooding.

The government of North Rhine-Westphalia designated this protected area in 2005 to preserve the natural state of the Sengbach river valley. This protection aimed to secure the ecological functions of the river and its floodplains for the long term.

The reserve's name refers to the floodplain (Aue) of the lower Sengbach valley, the stretch between the Sengbach dam wall and the stream's mouth on the Wupper near Glüder. The Sengbach's flow swings sharply: the upper course can dry out in summer, while water spills over the dam in flood. The damp meadows and fallow ground draw a rich insect fauna, including the sickle-bearing bush-cricket and the wasp spider recorded in the 2005 landscape plan.

Marked walking trails run throughout the reserve with several entry points accessible from Solingen. Visitors should wear sturdy footwear, as wet grassland can be soft after rain and forest floors are uneven.

The Sengbach's flow varies sharply because of the Sengbach Dam upstream: the upper course can dry out in summer, while overflow from the dam causes flooding. Despite this, the water remains largely unpolluted. The reserve is also home to the bullhead (Cottus gobio), a fish listed in the EU Habitats Directive.