From there, a secondary forest road goes north-west to the peninsula south of the mouth of the Portneuf East river.

The mountainous topography of the Portneuf East River hinders the development of a forest road for this valley.

The main hydrographic slopes neighboring the Portneuf East River are: The Portneuf East River rises at the mouth of Lake Emilien (length: 1.8 kilometres (1.1 mi); altitude: 579 metres (1,900 ft)) surrounded by mountains.

[1] From Lac Émilien, the Portneuf Est river generally flows east, then south-east, entirely in forest areas over 37.7 kilometres (23.4 mi) according to the following segments: Upper course of the Portneuf East river (segment of 24.3 kilometres (15.1 mi) altitude: 523 metres (1,716 ft)) over its full length and Lake Ale (length: 0.8 kilometres (0.50 mi); altitude: 512 metres (1,680 ft)) over its full length, as well as by forming a curve towards the South, up to the discharge (coming from the North) of a set of lakes including Éric, Garant, Noir, Épinette, Cameo and Élie; Note: Lac Charles receives the outlet (coming from the Southwest) from Lac du Chicot; Lower course of the Portneuf East river (segment of 13.4 kilometres (8.3 mi) The Portneuf East River flows in a curve from the East bank of the Portneuf River at the head of a series of rapids stretching 0.5 kilometres (0.31 mi) to the South.

This confluence is located at: The toponym "Rivière Portneuf Est" was formalized on December 5, 1968, at the Place Names Bank of the Commission de toponymie du Québec.