The river drains into Oyster Harbour along with the King River. The geography of the river includes steep hillsides, forests, farmland, and small granite outcrops. The river flows through two pools: Meriwarbelup Pool and Noorubup Pool. The upper part of the river lies within the National Park, and there are several tributaries that flow into the Kalgan River.

The history of the Kalgan River is rich. It was named “Riviere des Francais” by Captain Nicolas Baudin during the French Scientific Expedition in 1803. It became known as the “French River” by early settlers. The river was recorded as “Kal-gan-up” by explorer Alexander Collie in April 1831, which is believed to be the Noongar word for “place of many waters” or “place of fish.” The Albany Fish Traps have been situated here for thousands of years.

The flora along the Kalgan River is diverse. The estuarine section is dominated by saltwater paperbark trees surrounded by coastal saw sedge and shore rushes. The freshwater areas have a greater variety of plant species, including swamp paperbark, marri, jarrah, wattle, and Western Australian peppermint trees. In areas where native species have been lost, erosion of the riverbank has become a problem. Many wildflowers can be found along the Luke Pen Walk.

The Kalgan River is renowned for its fishing opportunities and is home to