The Tonge meanders southwards, to the east of Bolton, past Springfield where it is joined by Bradshaw Brook, at the end of its route from the Jumbles and Wayoh reservoirs, close to Tonge Fold.

[1][2] The 0.7-hectare (1.7-acre) site comprises the steep west right bank of the river.

It was designated an SSSI 1987 for its geological interest, principally the fluvial sandstone which has yielded pteridosperm seeds, known as Trigonocarpus.

The well preserved nature of the seeds make it of considerable sedimentological and palaeogeographic interest.

In 2017, invasive walking catfish Clarias were recovered from the river.