The Semois, from Chiny to Herbeumont and from Herbeumont to Bohan. Sometimes meandering between steep rocky slopes or spreading its meanders more gently in the alluvial plain that it creates in less rocky areas, the Semois has varied and diversified facies: rapid and torrential areas between scattered blocks of rock, shallow riffles , deeper areas of calm water.

The Semois, given its width and its average slope (across the entire route), is the favorite zone of the barbel which finds in rich and calm waters enough to prosper and grow. The shallow areas of the riffles are used by the species for reproduction, while the calmer and deeper areas, bordered by alders, provide it with plenty of hiding places and food. But the barbel is not alone in appreciating the situation: chub, dace, hotus, spirling bleak, common bleak, roach, eel, perch, etc. are found here in large numbers while in the faster and well oxygenated areas grayling and trout are present everywhere. Minnows, loaches, gudgeons, tench, pike... complete the picture and no less than thirty species of fish can be present. Species of Community interest, listed among the species protected by the Natura 2000 Directive, such as the sculpin, the European lamprey, the rare river loach or even the mountain hog. The Semois is therefore a paradise for fishermen… among these are also the gray heron and the kingfisher whose blue flash of flight and shrill cries will often accompany the descents. From autumn, they are joined by the great egret or by groups of goosanders (splendid ducks with a pointed beak ending in a hook and a belly swathed in salmon); for the past ten years these birds have chosen to winter in increasing numbers on certain Walloon rivers, thus joining the native mallards or other little grebes…. It will be easy to distinguish them from the great cormorants with black plumage which frequent the Semois all year round but which form large groups there in winter, especially in the dormitory trees adopted for the night. Dippers, gray wagtails or streams frequently flutter from stone to stone as boats pass. The Semois is a watercourse par excellence where large populations of aquatic buttercups develop; their long green hairs and their whitish flowers sometimes invade the entire width of the stream in certain places. These aquatic vegetations are part of the plant formations recognized as Natura 2000 habitats in waterways. In addition to the forest massifs (beech groves, oak groves and spruce groves), the Semois valley has large areas of wet meadows. These plots, which are regularly flooded by floods, have a great floristic diversity and make up very beautiful bouquets along the watercourse. These are very often natural habitats protected by the Natura 2000 Directive: megaphorbiaaies and wet hay meadows. These plant formations are unfortunately more and more invaded by invasive plants: Himalayan balsams which, if they form pretty pinkish bouquets on the banks, nevertheless do so to the detriment of the native vegetation. In autumn or winter, you may be lucky enough to surprise a group of European mouflons that come to graze in the valley. Deer and goats or even stags and hinds will also sometimes be seen randomly during your discreet movements. The European beaver is also present everywhere in Semois. Traces of its passage are therefore clearly visible: trees, gnawed or sharpened in pencils, shavings, long setting paths ... are easily identifiable. The beaver is protected in Wallonia.