It covers the vast majority of the shire, crossing it from north to south, and flows into the river Besòs, near Barcelona.

Throughout the comarca, it crosses alluvial clay terrains, which erodes easily, causing the river to carve a deep path into the soil.

More recently, because of the Catalan textile crisis, most of the factories were abandoned or reconverted for other uses, lessening the strain on the river's water quality.

Recently, there have been initiatives to recover the Ripoll for community recreation,[2] by restoring the river, which had deteriorated due not only to industrial pollution but also to the shanty towns made by immigrants who came to work in the mills from Southern Spain during the 1960s.

In 1962, the Vallès Occidental suffered a period of strong floods followed by winds that devastated the shire and caused hundreds of deaths.