Salmons Brook

Running through wasteland and under the Lea Valley Lines railway, it is quickly joined by the outflow of the Deephams Sewage Treatment Works.

[6][7] As a west bank tributary of the lower River Lea, Salmons Brook came into being about 400,000 years ago, after the Anglian glaciation.

Until the Anglian glaciation, the River Thames flowed north-eastwards via Watford, through what is now the Vale of St Albans, then eastwards towards Chelmsford and the North Sea.

[8] Prior to the Anglian glaciation, a "proto-Mole-Wey" river was flowing northwards from the Weald and North Downs, through the "Finchley depression" and Palmers Green, to join the proto-Thames somewhere around Hoddesdon, at what is today an altitude of around 60 metres.

They, and their own tributaries, cut down successively through till left by the ice sheet, then through "Dollis Hill Gravel", and then into Claygate Beds and London Clay below.

[14] During the course of the following 400,000 years, the lower Lea moved steadily eastwards, leaving river terrace deposits of decreasing age and altitude as it did so, as well as a relatively steep eastern slope.

From Hadley Road down to Grange Park, Salmons Brook, like the lower River Lea, has a notably steep eastern slope.

But we are currently in an interglacial period, and the stream would have been flowing more strongly than today at times of "high discharge, under cold climatic conditions".

Furthermore, as the River Lea itself cut down as it moved eastwards, it lowered the base level of its tributary stream, Salmons Brook.