The Yonne emerges in a peat bog on Mont Préneley, 2,421 ft (738 m) above sea level. The river comes into play in the heart of the forest of La Gravelle, southeast of Château-Chinon in the Morvan region. Its flow being always low and its depth sometimes reaching only 1 ft (30 cm), it was mainly used to transport driftwood, coal, and wine. It was necessary to build bypass canals (Épizy, Nivernais, and Bourgogne canals) around 1790 and nearly 26 locks so that larger boats could increase the Yonne's trade. Today, they mainly receive tourists, nature lovers, and river vacationers.