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
Gibbon River Gibbon River The Gibbon River flows east of the Continental Divide in Yellowstone National Park, in northwestern Wyoming, the Northwestern United States. Along with the Firehole River, it is a major tributary of the Madison River, which itself is a tributary of the Missouri River. The Gibbon River rises in the center of the park at Grebe Lake. It flows for a short distance into Wolf Lake. Below Wolf Lake, the river flows through Virginia Cascades into the Norris valley. It flows near the Norris Geyser Basin and through the Gibbon Geyser Basin. From there it flows through the Gibbon