Kent coastline of Kent is continuously changing, due to tectonic uplift and coastal erosion. Until about 960, the Isle of Thanet was an island, separated by the Wantsum channel, formed around a deposit of chalk; over time, the channels silted up with alluvium. Similarly Romney Marsh and Dungeness have been formed by accumulation of alluvium. Kent's principal river, the River Medway, rises near East Grinstead in Sussex and flows eastwards to Maidstone. Here it turns north and breaks through the North Downs at Rochester, then joins the estuary of the River Thames as its final tributary near Sheerness. The Medway is
River Esk, Dumfries and Galloway River Esk, Dumfries and Galloway The River Esk (), also called the Border Esk, is a river in Dumfries and Galloway, Scotland, that flows into the Solway Firth. It also flows for a small way through the English county of Cumbria before entering the Solway. The river rises in the hills to the east of Moffat and its two main tributaries, the Black Esk and the White Esk, merge at the southern end of Castle O'er Forest. It flows south east through Eskdale past Langholm before merging with Liddel Water (which defines the border between Scotland and England. Before passing