The River Ash is a small, shallow river in Surrey, England. Its course of is just outside Greater London. Work has been carried out to re-align, clear, build up a small, Littleton head of water and create two backwaters. One backwater dates to the medieval period; the other to the 1990s decade. It flows as one of the six distributaries of the River Colne from the south of Staines Moor immediately south of the Staines Bypass eastwards through the rest of the borough of Spelthorne before meeting the River Thames. It is not navigable to craft and is rich in plant and insects, particularly reeds, diverse sedges (many of which commonly called bulrushes), pond-skaters, amphibians and lepidoptera (moths and butterflies). It enhances the Ash Link Nature Reserve, Studios Walk woodland biodiversity site and two parks. It is recognised as a key ecological feature within its Borough. Course The river is a distributary of the Colne. It forms the traditional boundary of Staines-upon-Thames first with Stanwell then with Ashford. It then turns southward and splits Littleton (specifically the Queen Mary Reservoir, then a thin nature reserve by Shepperton Studios) from Laleham. It then resumes eastward. It is the northern limit of diminutive, near-square Shepperton Green — the western third of which was for centuries a southern outcrop (projection) of Littleton, and remains so in the Anglican church system. Eighteen-hole Sunbury Golf Course on high-landscaped former municipal waste landfill then opposes a little of Shepperton across the banks. Then a farm of Green Belt straddles the river partly in outer lands of Sunbury-on-Thames. The river joins the Thames, flowing gently into the Creek – a secondary weirstream of the Thames – facing a long residential island: Wheatley's Ait. It marks two streets' garden ends, many of which have built footbridges. The five urban centres in the borough are well over 500 m away, which has spared it from pollution and supported its biodiversity. Three parks feature the river such as a long walk in Fordbridge Park, Ashford. Canoeists avoid the river when deep enough to canoe due to short barrages, extreme narrows and culverts. Flow In terms of flow of the distributaries, it is mid-ranked: flow exceeds: Sweeps Ditch, Staines (perhaps no longer a distributary of the Colne since building works in the 1970s) The long but ornamental Duke of Northumberland's River The Longford River. flow normally dwarves: the short final main