Thames the River Thames

The tidal section

Below Teddington Lock (about 55 miles or 89 kilometres upstream of the Thames Estuary), the river is subject to tidal activity from the North Sea. Before the lock was installed, the river was tidal as far as Staines, about 16 miles (26 km) upstream.^[24] London, capital of Roman Britain, was established on two hills, now known as Cornhill and Ludgate Hill. These provided a firm base for a trading centre at the lowest possible point on the Thames.^[25]
A river crossing was built at the site of London Bridge. London Bridge is now used as the basis for published tide tables giving the times of high tide. High tide reaches Putney about 30 minutes later than London Bridge, and Teddington about an hour later. The tidal stretch of the river is known as "the Tideway". Tide tables are published by the Port of London Authority and are available online. Times of high and low tides are also posted on Twitter.
The principal tributaries of the River Thames on the Tideway include the rivers Crane, Brent, Wandle, Ravensbourne (the final part of which is called Deptford Creek), Lea (the final part of which is called Bow Creek), Roding, Darent and Ingrebourne. At London, the water is slightly brackish with sea salt, being a mix of sea and fresh water.
This part of the river is managed by the Port of London Authority. The flood threat here comes from high tides and strong winds from the North Sea, and the Thames Barrier was built in the 1980s to protect London from this risk.
The Nore is the sandbank that marks the mouth of the Thames Estuary, where the outflow from the Thames meets the North Sea. It is roughly halfway between Havengore Creek in Essex and Warden Point on the Isle of Sheppey in Kent. Until 1964 it marked the seaward limit of the Port of London Authority. As the sandbank was a major hazard for shipping coming in and out of London, in 1732 it received the world's first lightship. This became a major landmark, and was used as an assembly point for shipping. Today it is marked by Sea Reach № 1 Buoy.