Dam, where’s all the water gone?

We’ve started work on the Trewint Street Fish Passage!

Fish passage on the River Wandle is impeded by over 30 in stream structures, the majority of which are weirs left from the milling era. These weirs and structures are a barrier to the movement of fish both up and downstream and also fragments and isolates habitats.

The Weir

Trewint Street is one of the significant barriers to fish passage, with two weirs either side of a large concrete island. With funding from the Environment Agency, Thames Water and Defra’s Catchment Partnership Action Fund (CPAF), we have started our project to install baffles and a fish pass to the right hand side weir, allowing the movement of fish once more!

The pass will also benefit European Eel populations which have declined by over 98% in the last 15 years, with barriers to movement being a contributory factor.

So what are we doing?

Low cost bafflesOn the right side channel, a series of baffles will be installed to the upper section of the concrete weir. These baffles are made from recycled plastic and fixed to the weirs in rows.  They slow the flow down on the weir, deepening the water and allow fish to swim up the weir through notches cut into the baffles (Image, Fishtek).

Barrages

In the lower part of the right hand channel, three notched barrages will be created to reduce the drop in water level between the channel and baffles. This will allow fish to easily swim up through the notches and through the baffles to new habitats beyond (Image, EA).

What will you see?

You will see a lot of building work on site over the next month as our contractors (Amenity Water Management (AWM) get started. You’ll also notice that the right hand channel is a lot drier than normal…

Dam!

Amenity Water Management have created a sandbag dam to keep the channel dry allowing them to work on installing the structures. All will return to normal once work is complete.

We’ll keep you posted with updates as always, but for now Tim is just happy to have wet feet again!

Tim happy once more

2 thoughts on “Dam, where’s all the water gone?

  1. Rob Thorp

    Hi Theo,
    Is that the right hand channel looking downstream, or the right hand channel looking upstream, please? As are kayaking club are planning a paddle down the Wandle at some point this month, and we would normally paddle down the right hand side, looking downstream.
    There is no easy way to portage around that area if we can’t kayak through it, so we would probably need to postpone the paddle.
    Please can you let me know some more details.
    Many thanks,
    Rob Thorp

Leave a Reply

Your email address will not be published. Required fields are marked *

Optionally add an image (JPEG only)