Viroin Valley of Olloy at Mazée

The Viroin, which originates in Nismes at the confluence of the Eau Blanche and Eau Noire, flows for about fifteen kilometers before emptying into the Meuse at Vireux-Molhain, a village in the French Ardennes. Between Olloy and Treignes, the river delineates the boundary between the Ardennes slope and the Calestienne, two regions that are very contrasting in terms of climate, ecology, and geomorphology. It meanders extensively there, making its course particularly picturesque. Originally occupied by wet forests and later, until the mid-20th century, by meadowland, the floodplain has changed significantly today, although it has retained multiple interests. Botanically, the valley is notable for the presence of several remarkable species, particularly confined to fragments of riparian forest: two-leaved squill (Scilla bifolia), yellow gagea (Gagea lutea), false buttercup anemone (Anemone ranunculoides), scaly lathraea (Lathraea squamaria), smooth elm (Ulmus laevis), etc. The vertical banks of the river allow for the nesting of the sand martin (Riparia riparia), which is unfortunately threatened, and the kingfisher (Alcedo atthis). The dead arms and remaining wet meadows shelter several species of amphibians and the grass snake (Natrix natrix), which can be locally abundant. Finally, the pebble beaches are frequented by an impressive dragonfly, the club-tailed dragonfly (Onycogomphus forcipatus), as well as a discreet but highly specialized fauna, mainly consisting of ground beetles, rove beetles, and spiders.

Public Access: Some sections are leased by several fishing companies. The river is also utilized for kayak rentals. Access is possible along the paths and trails, but can sometimes be very difficult in wet weather due to the nature of the terrain (especially on the Ardennes slope).
Type: Site of Great Biological Interest (SGIB)

La biodiversité en Wallonie