The water level of the river varies with the seasons and the precipitation; the spring flood occurs in March or April.

The "rivère à l'Île" rises from a Dame Deux lake (length: 0.5 kilometres (0.31 mi) in the form of a fine; altitude: 698 metres (2,290 ft)) located in the north-central part of Château-Richer.

The Île river includes another island with a length of 1.6 kilometres (0.99 mi) located downstream from the outlet of Lac Thibeault.

[2][3] Since December 13, 1996, the toponymic designation "Rivière à l'Île" has also applied to the bed of a stream to the east, which was officially called "Bras du Nord" from February 4, 1982.

[4] The toponym "Rivière à l'Île" was formalized on December 13, 1996 at the Commission de toponymie du Québec.