From the Wikipedia page [1]
Channelsea River is a tidal river in London, England, one of the Bow Back Rivers that flow into the Bow Creek part of the River Lea, which in turn flows into the River Thames. Bow Creek provided the final outfall to the Thames, and the other channels were called Abbey Creek, City Mill River, Prescott Channel, Pudding Mill River, Three Mills Back River, Three Mills Wall River and Waterworks River. Below Bow Locks the creek forms the boundary between the London Boroughs of Newham and Tower Hamlets, in east London
In 1957–8, the Channelsea River was culverted between Stratford High Street and Lett Road.
In 1994, the historian Dan Cruickshank discovered 4,000 tons (60%) of the lost Euston Arch buried in the bed of the River Lea at the Channelsea River and the Prescott Channel.
Channelsea Island is located on this river.