The River Effra is a former stream or small river in south London, England, now culverted for most of its course. Once a tributary of the River Thames, flows from the Effra were incorporated in the Victorian era into a combined sewer draining much of the historic area of Peckham and Brixton.
Etymology
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 for the name's origin include Ruskin's, that it was "shortened from [the Latin word] Effrena", that it was from a Celtic root "yfrid", or that it derived from Anglo-Saxon "efer", "bank", perhaps via "heah efre" ("high bank") recorded in a charter of 693 for a spot on the bank of the Thames. By the 1790s the land making up the Manor of Heathrow 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.
The upper, southern parts of the river became increasingly suburbanised as the 19th century went on. The art critic John Ruskin, who grew up at Herne Hill close to one of the Effra's tributaries, described "the good I got out of the tadpole-haunted ditch in Croxted Lane", 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.
Post-industrial revolution
When the London sewerage system was constructed during the mid-19th century, its designer Sir Joseph Bazalgette incorporated flows from the River Effra into the southern division of the system. The Effra Branch Sewer, about 3 miles in length and costing some £19,400 to construct, received much of the Effra's surface water and ran from the Norwood area into the Southern High Level Sewer at Croxted Lane. The Southern High Level itself ran from Herne Hill eastwards under Peckham and New Cross to Deptford. A portion of Brixton Storm Relief Sewer was reconstructed in the 1970s around Brixton Road.
The outfall changed again with the construction of Thames Tideway Tunnel in the 2020s. An interception chamber was built into the Thames at Albert Embankment in front of Brixton Storm Relief CSO to intercept the effluence into the Tideway Tunnel. In the event of a sewer overflow, the Effra effluence could still be discharged to the Thames through a new outfall in front of the interception chamber, called Effra CSO.
Course
thumb|right|The Upper Norwood Recreation Ground, source of the main tributary of the Effra.
The river was fed by several tributaries which met above Brixton. The main branch of the Effra rises near Harold Road in Upper Norwood Recreation Ground, and flows through West Norwood. Where Norwood High Street merges at the fountain with the A215 to form Norwood Road, it was joined by a small tributary from Knights Hill ward.
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". Most of these tributaries are no longer visible above ground: an exception is the Ambrook, which still flows seasonally in Sydenham Hill Wood.
Folklore
thumbnail|left|upright|Boundary marker for Camberwell Parish on the course of the Effra at [[Gipsy Hill, where the watercourse was rediscovered in the 1920s.]]
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.
Flooding
Although little more than a stream in the south, until 1935 the culverted watercourse 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".