ISERE (anc. ISARA), tributary of the RhOne, south-east France, 18o m. long, with a descent of 7,55o ft. and a drainage area of 4,275 square miles. It flows through the departments of Savoie, Isere and Drome. It rises as a torrent in the Galise glaciers of the French Graian alps, and has successive sections of its course orientated south-east, north-west and north-east-south west, crossing the geological outcrops for the most part obliquely, and receiving the Arly and Arc, among other streams. After tra
versing the northern part of the axis of the Belledonne chain, it enters the wider Graisivaudan valley, floored by Jurassic strata, which is parallel to the Belledonne and flows south-westward to its union with its southern feeder, the Drac, just below Gren oble; it becomes navigable at Montmelian.