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Lewell Mill Flow Deflectors

With many thanks to the West Countries Rivers Trust the Frome Piddle & West Dorset Fisheries Association is funding a habitat improvement project on the Frome, Main River and the South Stream at Lewell Mill, West Stafford

This project involves the construction of nine new willow deflectors and the restoration of four narrowing burns.
Lewell Mill 1 Restoration of Willow burns. (Constructed with EA funding over ten years ago.)
Lewell Mill 2 Flow deflectors.
Lewell Mill 3 Flow deflectors.

Work took place in the early autumn of 2010 when the water level was at its lowest, salmonid movement at a minimum, and any breeding of mammals and birds finished, in fact there is no negative ecological impact on the area.

The work was carried out by Casterbridge Fisheries Ltd staff and over seen by the FP&WDFA project manager.

To create new willow flow deflectors to overcome the very uniform flow in this area, displacing some of the silt build up also adding natural woody debris encouraging various invertebrates, possibly native Crayfish and creating another suitable area to encourage spawning Salmon.

These structures soon become the home of both 0+ Salmon and Trout Parr as well as mature adults.

The posts for all the flow deflectors were driven in by hand, with 500mm centres and driven well into the bed of the river to a depth of at least 750mm to prevent any movement. (Existing posts still in place for the burns).

Some of the willow needed to create the structures was harvested on site, and additional willow harvested from a short distance upstream.

The flow deflectors have the brash made into large bundles, placed on the upstream edge of the posts, these bundles are then wired firmly into place, and the thick ends of the willow brash pushed into the bank to encourage the whole structure to grow.

The mattress burns, rebuilt using live willow, (previous hazel faggots washed out) were firstly woven around the outside stakes creating a solid framework before tightly filling the whole burn with willow mattress, and then the structure is wired in tightly to prevent any winter wash out.

The above picture shows two of the live willow burns which have narrowed the river and created a meander.

As soon as these burns were re instated the flow increased removing the blanket weed from the bed of the river, and started to move fine sediment that had been deposited over the summer’s low flow.

The structures over the winter months gather and collect silt, providing nutrients and a firm base for the willow to grow come the following spring, extending the life of these enhancements, with the need for minimal maintenance, and providing material for future use.

Casterbridge Fisheries Limited  john@riverworks.co.ukwww.riverworks.co.uk