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The River Thames

Originally, the river flowed further to the north, through Buckinghamshire to Essex, before becoming a tributary to the River Rhine.  Around 475,000 years ago glaciers forced the river southwards along its present course.

The river is now tidal as far as Teddington, 90km upstream from the Thames estuary; but when the Romans arrived, it was probably only tidal as far as the site of Londinium (now the City of London). This may be one of the reasons why the Romans established a settlement here.

Up until the late 19th century, the river was wider with a slower tidal flow.  The building of old London Bridge also slowed down the river.  In very cold winters the river froze over and ‘frost fairs’ were held on the ice.

Old London Bridge was demolished in 1831 and a bridge with much wider arches was built.  With the building of new Thames embankments between 1864 and 1870 the river became narrower, faster and deeper.  The river has never really frozen since that time.

London is now sinking at an estimated 12 inches (30cm) every 100 years.

People and the river

Dredging the River Thames

Human activity has always had a significant effect on the river.  By the middle ages the river was an important resource for transport, waterpower, and food. From the earliest times, boats were used to carry food, trade goods and people up the river into the heart of England.  Trout, salmon and eels were caught in large numbers all along the Thames.

In the non-tidal upriver reaches, mills for grinding corn were common.  However, the weirs needed for the water wheels made navigation difficult for barges and boats.  This situation was eased after the introduction of lock gates in the early 17th century.

By the 15th century, shipyards were appearing east of London at Shadwell, Rotherhithe and Deptford.   However, until the early 19th century, much of the riverside east of London was formed of marshy wetlands and agricultural land, and there were rich pastures at Greenwich, West Ham, East Ham and Blackwall, and on the Isle of Dogs. The establishment of the dock systems at this time brought heavy industrialisation and pollution to the riverside.

A polluted stream

Straightening the Thames

The Corporation of the City of London was responsible for managing the river until 1857 when the Thames Conservancy was established.   Both organisations struggled to conserve fish stocks and keep the river clear for vessels.

Chemicals from industries like the riverside gasworks, and sewage from the rapidly growing population of London, resulted in heavy pollution of the river.

Unfortunately, the river had always been the main source of drinking water.  In 1581 water wheels were erected under London Bridge to supply water to the City, and  from the early 18th century private water companies used largely untreated water straight from the river to supply the growing population. 

By the 1830s, the pollution of the river resulted in an outbreak of cholera among the population.  The river became deprived of oxygen, and fish stocks virtually disappeared.

In the late 1850s, the stench from the river was so great that MPs were forced to abandon the House of Commons.  The engineer Joseph Bazalgette was brought in to design a new sewer system that would divert the city’s sewage miles downstream.  However, raw sewage dumped downstream still washed back in on the flood tide.

From the 1960s onwards, with the closure of the docks, efforts began to be made to clean up the river.  Despite occasional overflows from London’s Victorian sewage system during heavy rain, the river is now one of the cleanest urban waterways in Europe.  Salmon are common and porpoise, seals and even dolphins have been spotted, sometimes as far upstream as London Bridge.