The Toulourenc torrential river to the north side of Mont Ventoux, defines the departments of Vaucluse and Drome. It rises at the foot of the castle of Aulan near Montbrun-les-Bains, runs almost 30 kilometers before it flows into the Ouvèze about the town of Entrechaux .
Sinuant according valleys down the mountain, she dug into the rock bed, upstream and downstream of the hamlet of Veaux deep gorges sometimes reaching 100 meters.
The downstream gorge called "Estrechon" (because of its narrowness) does not exceed in places 1, 50 meter wide and has a length of 3 kilometers, from Our Lady of Angels in Calves.
Above the hamlet after another Estrechon collapse block serves as a river bed,
then gorges continue until Saint-Léger-du-Ventoux
"Font de Martin" make this source, a flow rate of 30 to 100 l / s, springs on the right bank of the river, between Saint-Léger-du-Ventoux and Brantes . During the summer, it is the only significant water supply to Toulourenc. Its origin is in the permeable limestone pockets Ventoux that store atmospheric precipitation North Slope.