The tidal section

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 lowest possible point on the Thames. 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.

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 1980’s to protect London from this risk.

Wildlife

Various species of bird feed off the river or nest on it, some being found both at sea and inland. These include Cormorant, Black-headed Gull, and Herring Gull. The Swan is a familiar sight on the river but the escaped Black Swan is more rare. The annual ceremony of Swan upping is an old tradition of counting stocks. Non-native geese that can be seen include Can; Geese, Egyptian Geese, and Bar-headed Geese, and ducks include the familiar native Mallard plus introduced Mandarin Duck and Wood Duck. Other water birds to be found on the Thames. In addition there many types of British birds that live alongside the river, although they are not specific to river habitat.

The Thames contains both seawater and freshwater, thus providing support for seawater and freshwater fish. The salmon, which inhabits both environments has been reintroduced. Some of the freshwater fish to be found in the Thames and its tributaries include brown trout, chub, dace, roach, barbel, perch, pike, bleak, and flounder. Colonies of short-snouted seahorses have also recently been discovered in the river.

In addition the Thames is host to some invasive crustaceans including Signal crayfish and Chinese Mitten Crab.

On 20 January 2006 a northern 16-18 ft (5 m) bottle-nosed whale was spotted in Thames and was seen as far upstream as Chelsea. This is extremely unusual because this type whale is generally found in deep sea waters. Crowds gathered along the riverbanks to witness extraordinary spectacle. But it soon became clear there was cause for concern, as the animal came within yards of the banks, almost beaching, and crashed into an empty boat causing slight bleeding. Approximately 12 hours later, the whale was believed to be seen again n Greenwich, possibly heading back to sea. There was a rescue attempt lasting several hours, but it eventually died on a barge.

Date: 2015-01-02; view: 929