Geography of Kent and Dungeness have been formed by accumulation of alluvium. Kent's principal river, the River Medway, rises near Edenbridge and flows some 25 miles (40 km) eastwards to a point near Maidstone, when it turns north. Here it breaks through the North Downs at Rochester before joining the River Thames as its final tributary near Sheerness. The river is tidal as far as Allington lock, but in earlier times cargo-carrying vessels reached as far upstream as Tonbridge. The Medway has captured the head waters of other rivers such as the River Darent. There are other rivers in Kent, most notably the
Black River (Chehalis River) Black River (Chehalis River) The Black River is a river in Thurston County in the U.S. state of Washington. It is approximately long with a drainage basin of about . The Black River's source is Black Lake, located about west of Tumwater. The river flows generally south, through the Mima Mounds State Natural Area, then southwest, passing by Rochester and entering Grays Harbor County, then emptying into the Chehalis River in the Chehalis Indian Reservation. The fur trader John Work was the first to describe the Black River in 1824: "The Black River so named from the colour of its