The Dives flows over approximately 65 miles (105 km) across the Orne and Calvados departments. It extends from its source, at 492 ft (150 m) above sea level in Courménil near Exmes, to its mouth in the English Channel between the dunes of Cabourg and the marina of Dives-sur-Mer. This mainly south-north oriented watercourse with an average slope of 2‰ drains downstream from Mézidon-Canon a vast zone of marshes that extends almost to its mouth. True natural strongholds, these salt marshes and mudflats subject to estuarine dynamics form interface zones between land and sea and present a remarkable ecological diversity.