This valley is mainly served by the Lac-des-Roches road which passes on the north bank of this watercourse.

Forestry is the main economic activity in this valley; second resort; agriculture (in the lower part around the village of Côte-du-Lac), third.

The surface of the Lac river is generally frozen from the beginning of December until the end of March; however, safe circulation on the ice is generally done from mid-December to mid-March.

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

The "rivière du Lac" rises at the confluence of two forest streams (altitude: 270 metres (890 ft)), ie: Course of the Lac river From its source, the Rivière du Lac descends in a valley between the mountains, first in forest territory, on 4.1 kilometres (2.5 mi), with a drop of 105 metres (344 ft), according to the following segments: From the confluence of the Lac river, the current flows over 10.2 kilometres (6.3 mi) generally towards the south by the course of the Montmorency River, up to the northwest bank of the St. Lawrence River.