Thames Estuary

This limit of the estuary has been defined in two main ways:[1]

• The narrow estuary is strongly tidal and is known as the Tideway. It starts in south-west London at Teddington Lock and weir, Teddington/Ham. This point is also mid-way between Richmond Lock which only keeps back a few miles of human-made head (stasis) of water during low tide and the extreme modern-era head at Thames Ditton Island on Kingston reach where slack water occurs at maximal high tide in times of rainfall-caused flooded banks. In terms of salinity the transition from freshwater to estuarine occurs around Battersea;[2] east of the Thames Barrier the water is of notable brackishness where fish, particularly in dry summers on the flood (the incoming) tide, are estuarine.

• The head of Sea Reach – the Kent / Essex Strait – south of Canvey Island on the northern (Essex) shore. This reach and all more eastern zones (a mixture of channels and shoals) have a width that contributes to the large, archetypal, internal but mainly submerged sandbanks. These come from a combination of silt-borne fluvial and tidal scouring and deposition (silting).

London Stone, Yantlet Creek

The transition between the Thames Estuary and the North Sea has been located at various notional boundaries, including:[1]

• The Yantlet Line between the Crow Stone (London Stone) on the northern foreshore at Chalkwell, Westcliffe-on-Sea and another London Stone off the Isle of Grain, to the south. (This marked the seaward limit of the river jurisdiction successively of the City of London and the Thames Conservancy).
• A line between Havengore Creek, Essex (to the north), and Warden Point, east Sheppey, Kent (to the south), tallying with the easternmost hazardous point of the Nore sandbank. (This formed the seaward limit of the Port of London Authority on its establishment in 1908).[3]
• A line between North Foreland, Margate, Kent via the Kentish Knock lighthouse to Harwich in Essex. Here begin sandbanks of the bight of this shallow sea. Per a Hydrological Survey of 1882–9.[4] (This tallies with the eastern edge of the current seaward limit of the Port of London Authority as defined in 1964).[3]

The estuary is one of the largest of 170 such inlets on the coast of Great Britain. It constitutes a major shipping route, with thousands of movements each year, including: large oil tankers, container ships, bulk carriers (of loose materials/liquids), and roll-on/roll-off (ro-ro) ferries. It is the accessway for the Port of London (including London Gateway, associated Tilbury and Purfleet) and the Medway Ports of Sheerness, Chatham and Thamesport.

The traditional Thames sailing barge worked in this area, designed to be suitable for the shallow waters in the smaller ports.

Wind farms in the estuary, in this case the London Array.

A 2000s-decade-built wind farm is 8.5 km north of Herne Bay, Kent, on a shoal south-west of Kentish Knock. It is 30 wind turbines generating typically 82.4MW of electricity.

The much larger 630 MW London Array was inaugurated in 2013.

'Mapp' of the Thames Estuary by Capt. Greenvile Collins, 1698. (North is to the right; rhumb lines are shown. London is beyond the top left of the chart).

Provision of buoys and beacons for the purpose of navigation came relatively late to England (compared to the Netherlands, for example).[16] Instead, coastal navigators and pilots relied on the use of transits (the alignment of prominent structures or natural features on land) for guidance. In 1566 Trinity House of Deptford (which oversaw pilotage on the Thames) was empowered to 'make, erect and set up [...] beacons, marks and signs for the sea' (albeit at its own expense).[17] Not long afterwards, the decay of the steeple of Margate Church (an important landmark for negotiating 'the Narrows', a complex route between sandbanks used by vessels sailing to or from London along the North Kent coast) led to Trinity House marking the Narrows with buoys in the late 16th century.[16]

In his coastal survey of 1682-93, Greenvile Collins records five buoys around the Narrows, just north of Reculver, on the southern approach to the Thames. The Swin (the northern approach) was marked with buoys at the easternmost points of the Gunfleet, Middle and Buxey sands, and by beacons on the Whitaker, Shoe and Blacktail spits. A buoy marked the easternmost point of the Nore sandbank at this time, and three more buoys marked sandbanks in the middle part of the estuary (Spaniard, Red Sand and the Oaze).[16]

The Nore Lightship, the world's first lightvessel, was established in the Estuary as a private venture in 1732 to mark the 'best position for entering the Thames and Medway, and to clear the Nore Sand'.[18] The coastwise approach from the north was aided by the establishment of the Sunk lightvessel in 1802 'to mark the north-east entrance to East Swin, and to guide vessels round Long Sand'. Later, the Swin channel was further marked by lightvessels at Swin Middle (1837) and Mouse (1838), and by screw-pile lighthouses on the Maplin Sands (1841) and at Gunfleet (1856).[19] Meanwhile, one of the outlying sandbanks of the Estuary was marked by a lightvessel at Kentish Knock (in 1840); and in due course the southern approach was marked by lightvessels at the Tongue (1847) and Girdler (1848) sands, with another being added (between these two) in the Princes Channel (1856). In 1851 two more screw-pile lighthouses were built further upriver, on the northern foreshore of Sea Reach: at Mucking and on the Chapman sands (just off Canvey Island).

Prior to 1684 beacons were set up on the mudflats north of the Swin channel, to help vessels approaching the Thames from the north to navigate the sands. Pan-sand Beacon was set up by Trinity House in 1774 to mark a dangerous sandbank on the southern approach.[20] Similar daymarks were set up on other nearby sandbanks in later years, including on Margate Hook (1843), Middle Ground (1844) and Shingles (1846).[20] Trinity House also maintained beacons further upriver, including at Broadness (established in 1821), Stoneness (1839), Erith (1830) and Tripcock (1832).

In 1864 responsibility for maintaining the navigation lights of the River Thames between London Bridge and Yantlet was transferred by Act of Parliament from the Thames Conservancy to the Corporation of Trinity House; responsibility for buoyage was transferred likewise in 1878.[21] In 1885 the beacons at Broadness and Stoneness were replaced with iron-frame experimental lighthouses, each lit by a novel system which would allow the light to function unattended (except for a twice-weekly visit by a boatman for cleaning and maintenance). Broadness was lit by Pintsch gas, and Stoneness by a Lindberg light (which burned petroleum naphtha).[22] At the same time Trinity House began experimenting with the application of lamps to buoys, using Pintsch's oil-gas system, beginning with three in the Thames Estuary (East Oaze, Ovens and Sheerness Middle); the experiment was deemed a success and subsequently further buoys and beacons were lit by Trinity House using the same system, in the Estuary and beyond.[22]

Today the Port of London Authority's Thames Navigation Service (established in 1959) is responsible for buoyage, beaconage and bridge lights on the Tideway.[23] Trinity House remains responsible for aids to navigation in the wider estuary (and beyond).

This table shows, from west to east, the principal navigation lights, buoys and other marks to the north (port) and south (starboard) of the main deep-water channels of the River Thames from Gallions Reach to the Sunk Light Float.[24][25][26][27][28] The Thames is in IALA region A so port buoys are red and starboard buoys are green.