If Scar House reservoir overflows, water flows past Manchester Hole to Goyden Pot, another sinkhole.

The water sinking into the Nidderdale caves reappears at the rising Nidd Head to the south of the village of Lofthouse.

Below Lofthouse the river is joined by How Stean Beck, and turns south-south-east towards Ramsgill before flowing into Gouthwaite Reservoir.

Below the gorge, the river meanders south-east through the town of Knaresborough, heading north and looping south again as it enters flatter terrain.

The two most northerly reservoirs on the course of the river were built to provide water to the Bradford area in the early 1900s by way of the Nidd Aqueduct.

Around Lofthouse there are outcrops of Upper Yoredale limestone, which is more permeable than millstone grit and has created the Nidderdale Caves, where the river flows underground.

Lower down on the flood plain, the nature of the underlying ground is Magnesian Limestone over alluvium and terrace drift deposits.

[10][11] Where the river passes through the Nidd Gorge, Carboniferous (Namurian) and Upper Permian rock is exposed.

[14][15][16][17] The Nidd likely shares this etymology with the river and town of Neath (Welsh Nedd) in South Wales and the town of Stratton in Cornwall (originally named Strat-Neth), and with many other rivers across Europe, such as the Nete in Belgium, the Nied in France, Neda in Galicia (NW Spain), the Nethe, Nidda and Nidder in Germany, and the Nida in Poland.