River Medway. The River Medway is a river in South East England. It rises in the High Weald, East Sussex and flows through Tonbridge, Maidstone and the Medway conurbation in Kent, before emptying into the Thames Estuary near Sheerness, a total distance of 70 miles. About 13 miles of the river lies in East Sussex, with the remainder being in Kent. It has a catchment area of 930 square miles, the second largest in southern England after the Thames. The map opposite shows only the major tributaries: a more detailed map shows the extensive network of smaller streams feeding into the main river. Those tributaries rise from points along the North Downs, the Weald and Ashdown Forest. Former minor tributaries include the Old Bourne River, which flowed through the Brook, Chatham. The river and its tributaries flow through largely rural areas, Tonbridge, Maidstone and Medway being the exceptions. The Medway itself initially flows in a west–east direction south of the North Downs; at the confluence of the River Beult, however, it turns north and breaks through the North Downs at the Medway Gap, a steep and narrow valley near Rochester, before its final section to the sea. Until 1746 the river was not navigable above Maidstone. Below that point each village on the river had its wharf or wharves: at Halling, Snodland, New Hythe and Aylesford. Cargoes included corn, fodder, fruit, stone and timber. In 1746, improvements to the channel meant that barges of 40 long tons could reach East Farleigh, Yalding and even Tonbridge. In 1828, the channel was further improved up to Leigh. There are eleven locks on the river. The lowest, opened in 1792, is at Allington, and is the tidal limit. The others are at East Farleigh, Teston, Hampstead Lane, Stoneham Old Lock, Sluice Weir Lock, Oak Weir Lock, East Lock, Porter's, Eldridge's and Town Lock in Tonbridge. The locks will take craft up to 80 feet by 18 feet, and vessels with a draft of 4 feet can navigate the river. The shallowest point is just below Sluice Weir Lock, which is prone to silting after heavy rain. Small craft such as canoes can sometimes travel as far as Penshurst. The stretch from Leigh to Allington is known as the Medway Navigation, and is 19 miles in length. The Environment Agency is the navigation authority. One of the channels on the southern side of the estuary, Stangate Creek, is the subject of a painting by William Turner. In a location described as "opposite the Isle of Grain, Sharpfleet Creek, and the lower-end of the Hope", a quarantine site for ships was proclaimed on 16 September 1709, during an outbreak of the plague. The area had been leased to oyster fisherman, so compensation was paid to them. Nearly 150 ships quarantined there in the first six months of 1712, and the site was again used between 1721 and 1743. In 1918 to 1920, damages were sought for damage done to an oyster fishery in Stangate Creek. Until recently the lowest public crossing of the Medway was at Rochester, where there has been a bridge since Roman times. In the 14th century the Wardens and Commonalty of Rochester Bridge were instituted by Sir John de Cobham to pay for the rebuilding and upkeep of the bridge. Until 1963 the nearest crossing to Rochester Bridge was the 14th-century bridge at Aylesford, 12 miles upstream. Since then the following additional crossings have come into use: 1963: A viaduct over the river was built south of Rochester to carry the first section of the M2 motorway. In 2003 this was widened to two separate spans. Between 1963 and 1996 the M20 was built, with a bridge over the Medway south of Aylesford. 1996: The Medway Tunnel became the river's lowest public crossing, connecting Gillingham to Strood. The four-lane tunnel was constructed using the immersed tube method, and was partially paid for by Rochester Bridge Trust, the successor to the Wardens and Commonalty. 2003: A railway bridge 0.8 miles long, with a central span of 498 feet, was constructed for High Speed 1. The railway bridge lies parallel to the M2 motorway bridges. 2017: A new road bridge from the A228 between Holborough and Halling across to Hall Road, Wouldham, to facilitate the development of Peters Village. Three other major crossings are at Tonbridge, where bridges carry the A227 road and a rail link over the river; there is also a two-span viaduct which takes the A21 over the Medway Valley near Haysden. The lowest crossing of the Medway are two cable tunnels between the Isle of Grain and Chetney marshes. These were built between 1973 and 1976 in anticipation of the commissioning of Grain power station. The tunnels are 1700 m long, 2.54 m in diameter and between 34 and 47 m below ordnance datum; each carries a 400kV electricity circuit. There is no public access.