South East Rivers Trust

Of rock-ramps and fish


And the fish easement work on the Hogsmill continues. This time our work is focused on the river around the Thames Water Sewage Treatment works situated in Berrylands, Surbiton, specifically the stretch from the railway bridge down towards Kingston Cemetery.

The over-widened channel here reduces water depth which, along with three small weirs and a lot of concrete-lined channel in between, effectively prevents fish from moving upstream.

So these weirs will have to go. Or will they? Toby’s work connecting reaches of the Hogsmill to free fish movement has shown an alternative – slow the flow and over they go! Building rock ramps and pool passes drown out these structures enabling fish to navigate their way over them.

Illustration of a typical rock-ramp (Source: Thorncraft and Harris, 2000)
Illustration of a typical rock-ramp (Source: Thorncraft and Harris, 2000)

After a few essentials from the Environment Agency, Thames Water and Network Rail we ought to have this project going in the next couple of months. More to follow shortly…

Reference

Thorncraft G. and Harris, J.H. 2000. Fish passage and fishways in New South Wales: A status report, Technical Report 1/2000 prepared by NSW fisheries for Cooperative Research Centre for Freshwater Ecology.

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