Лондонның жоғалған Эфра өзені: тарихы мен ағымдағы жағдайы

The River Effra is a former set of streams in south London, England, culverted and used mainly for storm sewerage. It had been a tributary of the Thames. Its catchment waters, where not drained to aquifer soakaways and surface water drains, have been incorporated into 1850s built combined sewer sectors, devised by Sir Joseph Bazalgette. One drains Peckham, the other Brixton, then intended to flow towards Peckham. These generally flow east to be treated at Crossness. When it rains these sectors can purposefully backup and overflow in two Effra sewers that mirror a known and, from the study of medieval records, a suspected distributary. At least four of these limbs can operate to enable overflow, as opposed to normal flow, and it is not known how many Southwark distributaries ran before the known diversion to Vauxhall was made in the 13th century. Overflows reach two combined sewer overflows that will discharge into the Thames Tideway Tunnel on its completion in 2025. The 13th century ending, a WNW cut – then a dyke – was dug to cut across a low plain of the strip parish of Lambeth and is emulated by a key section of the Southern Low Level Interceptor sewer.

The etymology of the name "Effra" has been much disputed. There is no evidence that it was applied to the stream before the late 18th century, and early 19th century gazetteers gave it no name. A map of 1744 refers to it as the "Shore", and it was also referred to as "Brixton Creek" and "the Wash". Unlikely suggestions include Ruskin's, that it was "shortened from [the Latin word] Effrena", that it was from Celtic "yfrid", or that it derived from Anglo Saxon efer or efre, "bank". Bonner notes "heah efre" ("high bank") in a charter of 693 CE records a spot on the bank of the Thames. By the 1790s it was known as Effra Farm. There were also springs at a lower level in Dulwich; the various tributaries met near Brixton before flowing to the Thames. and made an early sketch of a bridge over it. Until about 1850, Brixton Road, where it ran along the course of the stream, was known as the "Washway", It still often flooded in heavy rain, and residents of Brixton Road and South Lambeth repeatedly complained of their houses being inundated. as far upstream as Herne Hill.

When the London sewerage system was constructed during the mid 19th century, its designer Sir Joseph Bazalgette incorporated flows from the Effra into the southern half of the system. The about 3 mile (5 km) Effra Branch Sewer cost £19,400 to build, received all but the Brixton outfall of the Effra could safely withstand and runs from Dulwich and Norwood into the Southern High Level Interceptor Sewer at Croxted Lane. This itself continues east from Herne Hill under Peckham and New Cross to Deptford. East along the watershed, springs rose in Dulwich Wood, flowing through Belair Park and beneath North Dulwich to Herne Hill. Still further to the east a tributary called the Ambrook rose from springs in Sydenham Hill Wood and Peckarmans Wood, flowing to Herne Hill through present day Dulwich Park, where its heavily landscaped channel is visible. The longest and easternmost tributary ran from Eliot Bank and Horniman Park in Forest Hill down to Herne Hill. Rocque's map of 1746 called these confluences around Herne Hill railway station "Island Green". These tributaries are no longer visible above ground: save for the Ambrook, which still flows seasonally in Sydenham Hill Wood.

A local story tells of a coffin found floating down the Thames in Victorian times, which was traced back to West Norwood Cemetery. Cemetery staff were puzzled to find that the plot the coffin had come from was undisturbed. Further investigation revealed that the ground beneath the grave had subsided, and the entire coffin had fallen into the underground Effra river, floating downstream to Vauxhall and entering the Thames.

Until 1935 a key part of the combined sewer flooded during heavy rains every decade or so; an inscription on a white stone tablet high up the side of a building in Elder Road, West Norwood reads: "FLOOD LEVEL 17th July 1890". After a three hour long storm on 14 June 1914, this section overflowed again and flooded houses along its path from Elder Road to Chestnut Roadlocals evacuated their damaged homes for several days. Further floods in the 1920s prompted works to enlarge the Effra Branch. This was sufficient until a very small number of homes flooded during the powerful downpours of 20 July 2007.

In 1992, a project by the London arts group Platform sparked a local campaign to dig up the river. The Unearthing the Effra project was based around a mock Effra Redevelopment Agency, which included a public office. The project gained publicity in local newspapers and radio stations before the journalists noticed that the group had scattered, the whole thing being a stunt carried out in the name of art.