The Aux Rochers River proper leaves the south end of Lake Walker and flows southeast for a further 30 kilometres (19 mi).

[3] A map of the Ecological regions of Quebec shows the river rising and flowing south through the eastern spruce/moss domain of the boreal zone.

Inland is an area with rounded rocky hills up to 400 metres (1,300 ft) high, extending north for 8 to 18 kilometres (5.0 to 11.2 mi).

There are areas of till less than 2 metres (6 ft 7 in) thick in the northern part, and the major valleys hold large deposits of glaciofluvial sediments.

The coastal plain has large quantities of clay and silt sediments deposited when the Goldthwait Sea invaded after the retreat of the Laurentide Ice Sheet.

[2] The Aux Rochers River and its longest tributary runs from north to south for a distance of 161 kilometres (100 mi), with a drop over this length of 585 metres (1,919 ft).

On the coastal plain the Aux Rochers River meanders slightly, then follows a rectilinear course where it has cut into the layer of glaciomarine sediments.

Wetlands cover 0.71% of watershed, mainly on the coastal plain with its flat relief and fine sediments.

It was formed by the flooding of an old trough-shaped glacial valley with very steep slopes that rise by over 400 metres (1,300 ft) in places.

[8][9] Aux Rochers River is also considered to be a scenic place and tourist destination as it has various areas of rapids and small falls.

The Larry Lake Old Forest, between the Ronald and MacDonald Rivers, covers an area of 8.33 square kilometres (3.22 sq mi).

In view of the rapidly declining Atlantic salmon population catch-and-release should have been implemented on all rivers apart from northern Quebec.