Thames Estuary facts for kids

Seen by the Operational Land Imager

Naval chart of the estuary, 1801

The Thames Estuary is where the River Thames meets the waters of the North Sea, in the south-east of Great Britain.

The limits of the estuary have been defined in several ways:

• Although physically the head of Sea Reach or the Kent / Essex Strait, south of Canvey Island on the northern (Essex) shore presents a western boundary, the Tideway itself can be considered estuarine; it starts in south-west London at Teddington/Ham.
• The Yantlet Line between the Crowstone in Chalkwell and the London Stone on the Isle of Grain.
• The Nore sandbank between Havengore Creek, Essex, and Warden Point, Kent.
• The eastern boundary of the estuary, suggested in a Hydrological Survey of 1882-9, is a line drawn from North Foreland, Margate, Kent via the Kentish Knock lighthouse to Harwich in Essex. The typical estuarine sandbanks extend to this line. The estuary downstream of the Tideway has a tidal movement of 4 metres, moving at a speed of up to 2.6 knots (4.8 km/h; 3.0 mph).
• A line from Warden Point on the Isle of Sheppey, Kent, via Sea Reach No. 1 buoys, to Havengore Head, Essex.

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, and roll-on/roll-off (ro-ro) ferries entering the estuary for the Port of London 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. More recently one of the largest wind farms in the UK has been developed in the estuary, located 8.5 km north of Herne Bay, Kent. The farm consists of 30 wind turbines generating a total of 82.4MW of electricity. The much larger 630 MW London Array was inaugurated in 2013.

This area has had several proposed sites for the building of a new airport to supplement, or to replace Heathrow/Gatwick. In the 1960s Maplin Sands was a contender; in 2002 it was to be at Cliffe, Kent. The new airport would be built on a man-made island in the estuary north of Minster-in-Sheppey.

There have also been discussions about the need for a Lower Thames Crossing in order to alleviate traffic congestion at Dartford.

The Thames Estuary is the focal part of the 21st-century toponym, the "Thames Gateway", designated as one of the principal development areas in Southern England.

Greater Thames Estuary

The upper part of the estuary from Tilbury to Mucking Creek looking north from Shorne, which is 4 kilometres (2.5 mi) south of the river

The appellation Greater Thames Estuary applies to the coast and the low-lying lands bordering the estuary. These are characterised by the presence of mudflats, low-lying open beaches, and salt marshes, namely the North Kent Marshes and the Essex Marshes. Man-made embankments are backed by reclaimed wetland grazing areas, but rising sea levels may make it necessary to temporarily flood some of that land in places at spring tides, to take the pressure off the defences.

The Blackwater Estuary, on the Essex coast, in the northern part of the Greater Thames Estuary. Mersea Island is on the right.

There are many smaller estuaries in Essex, including the rivers Colne, Blackwater and Crouch. Small coastal villages depend on an economy of fishing, boat-building, and yachting. The Isle of Sheppey, the Isle of Grain, Canvey Island, Two Tree Island, Havengore Island, New England Island, Rushley Island, Potton Island, Foulness Island and Mersea Island are part of the coastline.

Where higher land reaches the coast, there are some larger settlements, such as Clacton-on-Sea to the north in Essex, Herne Bay, Kent, and the Southend-on-Sea area within the narrower part of the estuary.

Salinity

The River Thames flowing through London is a classic river estuary, with sedimentary deposition restricted through manmade embankments. The district of Teddington a few miles south-west of London's centre marks the boundary between the tidal and non-tidal parts of the Thames. It is considered a freshwater river about as far east as Battersea, insofar as the average salinity is very low and the fish fauna consists predominantly of freshwater species such as roach, dace, carp, perch, and pike. The Thames Estuary becomes brackish between Battersea and Gravesend, and the diversity of freshwater fish species present is smaller, primarily roach and dace. Euryhaline marine species are more common, such as flounder, European seabass, mullet, and smelt. Further east, the salinity increases and the freshwater fish species are completely replaced by euryhaline marine ones, until the river reaches Gravesend, at which point conditions become fully marine and the fish fauna resemble that of the adjacent North Sea, including both euryhaline and stenohaline marine species. A similar pattern of replacement can be observed with the aquatic plants and invertebrates living in the river.

Channels

For commercial shipping approaching the Nore and thus London, main deep-water routes were the Princes Channel, the Queens Channel and the South Channel to the south, to a lesser extent the Kings Channel and the Swin to the north. The Swin was used by barges and leisure craft from the Essex rivers, and coasters and colliers from the north east. These channels were made up of natural troughs; Yantlet Channel (Sea Reach), Oaze Deep, Knock John Channel, Black Deep Channel which have been extensively marked. These are separated by slow moving sandbanks with names such as the East and West Barrows, the Nob, the Knock, the John, the Sunk, the Girdler, and the Long sands.

The shallow bottomed barges and coasters would navigate the swatchways at flood tide, and would cross the sand banks at spitways, points where the water was least shallow, and just deep enough at that point of the tide. If they missed the moment they would heave to and wait for the next tide.

Recreational craft are expected use channels most suited to the size of their vessel. When navigating to or from the north they should use the Middle Deep, Swin and Warp. Barrow Deep and Warp. When navigating to or from the south, they should use the Horse and Gore and Four Fathom Channels.

To cross the estuary large vessels used Fisherman's Gat, and small vessels to were expected to use Foulger's Gat.

Navigational marks

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. The Thames is in IALA region A so port buoys are red and starboard buoys are green.

Thames estuary navigation marks

See also

In Spanish: Estuario del Támesis para niños